SPECIAL R&D REPORT

ON THE FAO-VIET NAM

COFFEE PROJECT

TCP/VIE/2903 (A)

Nguyen Van Thuong, Tran Kim Loang, Phan Thanh Binh,

Ha Thi Mao, Ho Thi Phuoc, and staff of WASI,

Le Anh Tuan, Bach Than Tuan, Go Nuc Bin,

Pham Van Tam and staff of CAFECONTROL

Compiled by

Anthony Marsh, J. Michael Frank

and Keith Chapman

March 2006

SPECIAL R&D REPORT ON THE FAO-VIET NAM COFFEE PROJECT

TCP/VIE/2903 (A)

Nguyen Van Thuong, Tran Kim Loang, Phan Thanh Binh,

Ha Thi Mao, Ho Thi Phuoc, and staff of WASI, Le Anh Tuan, Bach Than Tuan, Go Nuc Bin,

Pham Van Tam and staff of CAFECONTROL

Compiled by

Anthony Marsh, J. Michael Frank, and Keith Chapman

March 2006

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Disclaimer The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Viet Nam Government or the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area of its authorities, or concerning the delimitation of its frontiers or boundaries.

Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged. All rights reserved. Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders.

For copies and applications for permission, write to:

FAO Regional Office for Asia and the Pacific 39 Phra Artit Road Banglamphu 10200 Bangkok Thailand

Tel: 66-2-6974000 Fax: 66-2-6974445 Email: FAO-RAP@FAO.ORG

Website: www.fao.org/world/regional/rap/highlights.asp

Acknowledgements The authors and FAO sincerely acknowledge the assistance given to both the FAO Project and the compilation of this report by the following people for their excellent support with implementation and facilitation of the project. Research staff of the Ministry of Agriculture and Rural Development (MARD)

Western Highlands Agro-Forestry Scientific Technology Institute (WASI), Buon Me Thout

CAFECONTROL Daklak, Buon Me Thout and CAFECONTROL HCMC

Staff of MARD in Hanoi

FAO in Viet Nam

Staff of FAO Regional Office for Asia and the Pacific, Bangkok.

The authors also wish to thank Loraine Chapman for her support and skills in desktop publishing this report.

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PREFACE Coffee quality improvement and Ochratoxin A (OTA) prevention are key issues for Viet Nam. With an annual production of around 800,000 MT of green bean coffee per year, Viet Nam is now the biggest producer and exporter of Robusta coffee in the world. No country, and especially Viet Nam, can afford to have coffee rejected by the world market for OTA contamination. Currently, Vietnamese coffee is discounted by approximately USD30/MT, as it is generally perceived by the world market to be of lower quality.

The challenge then, is to assure the world market that higher quality coffee can be produced that is free of OTA contamination. Wet weather at drying time, limited drying areas and slow drying, along with improper storage have been recognised as major contributors to lower quality coffee that is likely to be contaminated with OTA. Inexpensive, simple semi-wash/demucilaging technologies with enhanced rapid drying by smallholders has been shown to produce higher quality Robusta coffee, therefore attracting greatly improved prices of USD160/MT more in the world market.

In 2002, Viet Nam recognized these problems and sought FAO assistance to provide solutions. FAO, in collaboration with the International Coffee Organization (ICO) and the Institute for Scientific Information on Coffee (ISIC), had developed a project entitled, “Enhancement of Coffee Quality through Prevention of Mould Formation,” which was being financed by the Common Fund for Commodities (CFC), for seven countries during 2000 to 2005. However at that time, because Viet Nam was not a member of ICO or CFC, it did not qualify for assistance from the global project. Accordingly, FAO independently agreed to support a TCP project (TCP/VIE/2903 A) with its own funding entitled, “Improvement of Coffee Quality and Prevention of Mould Formation and Ochratoxin A (OTA) Contamination of Coffee in Viet Nam.”

This publication reports on some key outcomes of the project and provides a greater insight into on-farm issues as well as reporting on practical findings and R&D initiatives. We trust that you will find the publication useful in extending your knowledge on coffee and in providing solutions to problems of coffee quality and avoidance of OTA.

Keith Chapman, March 2006

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CONTENTS INTRODUCTION ............................................................................................................................ 7

Overall objective ..................................................................................................................... 7 Key outputs.............................................................................................................................. 7

TRIALS OF DOMESTIC AND IMPORTED WET COFFEE PROCESSING EQUIPMENT (SEASON 1:2003/04)..................................................................................................................................... 9

Summary.................................................................................................................................. 9 Introduction ............................................................................................................................. 9 Materials and methods ........................................................................................................... 9

Description of two Pulper / Mucilage removal machines ................................................................... 10 Descriptions of three coffee mashers ................................................................................................ 10

Methodology.......................................................................................................................... 11 Specific data collected from the trials ................................................................................................ 12

Results and discussion........................................................................................................ 12 Quality of cherry material................................................................................................................... 12 Major specifications of the processing machines .............................................................................. 13 Processing costs ............................................................................................................................... 14

Conclusions and recommendations ................................................................................... 15 Conclusions on the two pulper-mucilage machines........................................................................... 15 Conclusions on the three masher machines...................................................................................... 15 Recommendations ............................................................................................................................ 15

TRIALS ON DOMESTIC AND IMPORTED WET COFFEE PROCESSING EQUIPMENT REPORT 1: ARABICA COFFEE (SEASON 2: 2004/05) ................................................................................... 17

Summary................................................................................................................................ 17 Introduction ........................................................................................................................... 17 Objectives .............................................................................................................................. 18 Materials and methods ......................................................................................................... 18

Individual machine descriptions......................................................................................................... 18 Coffee used for processing trial......................................................................................................... 19

Methodology.......................................................................................................................... 19 Trial implementation .......................................................................................................................... 19 Specific outputs and data collected ................................................................................................... 19

Results and discussion........................................................................................................ 20 Key technical specifications of Arabica coffee processing equipment............................................... 20 Pulping and mucilage removal performance and quality dried coffee ............................................... 20 Physical quality of dry coffee ............................................................................................................. 20 Cup quality of dry coffee.................................................................................................................... 21 Direct costs to process/produce 1kg of green bean coffee................................................................ 21

Conclusions and recommendations ................................................................................... 22 Conclusions....................................................................................................................................... 22 Recommendations ............................................................................................................................ 22 PINHALENSE S/A MAQUINAS AGRICOLAS Rua Honorio Soares 80 Esp. Tso. Pinhal-SP Brazil CEP 13.990-000................................................................................................................................ 23

TRIALS ON DOMESTIC AND IMPORTED WET COFFEE PROCESSING EQUIPMENT REPORT 2: ROBUSTA COFFEE (SEASON 2: 2004/05)................................................................................... 24

Summary................................................................................................................................ 24 Introduction ........................................................................................................................... 24 Objectives .............................................................................................................................. 25 Material and methods ........................................................................................................... 25

Machines tested ................................................................................................................................ 25 Methodology.......................................................................................................................... 27

Trial implementation .......................................................................................................................... 27 Quality of Robusta cherry used in the trials ....................................................................................... 27

Results and discussion........................................................................................................ 27 Performance results of coffee processing machines ......................................................................... 27 Direct costs to process one kilo of green bean.................................................................................. 28 Pulping and mucilage removal performance ..................................................................................... 28 Physical quality of coffee produced ................................................................................................... 29

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Beverage/liquor quality of products ................................................................................................... 29 Conclusions and recommendations ...................................................................................30

Conclusions ....................................................................................................................................... 30 Recommendations............................................................................................................................. 30

STORAGE IMPACT ON ROBUSTA COFFEE QUALITY IN BOUN ME THOUT: RESEARCH RESULTS 2004/05 (PART I)......................................................................................................... 32

Summary ................................................................................................................................32 Introduction ...........................................................................................................................32 Objectives ..............................................................................................................................33 Materials and methods .........................................................................................................33

Materials ............................................................................................................................................ 33 Methodology ..........................................................................................................................33

Conditions of storage......................................................................................................................... 34 Data collected.................................................................................................................................... 35

Results and discussion ........................................................................................................35 Moisture content of coffee beans....................................................................................................... 35 Air temperature and relative humidity in the stores............................................................................ 36 Quality of green bean coffee.............................................................................................................. 37 Relationship between moisture content, water activity and rate of mould development in coffee beans................................................................................................................................................. 38 Cup Quality of coffee ......................................................................................................................... 43 OTA analysis ..................................................................................................................................... 43

Conclusions and recommendations ...................................................................................44 Conclusions ....................................................................................................................................... 44 Recommendations............................................................................................................................. 44 References ........................................................................................................................................ 44

EFFECTS OF STORAGE CONDITIONS ON FUNGAL OCCURRENCE IN GREEN BEANS OF ROBUSTA COFFEE, STORED AS GREEN BEAN, PARCHMENT AND CHERRY (PART II) .......... 49

Summary ................................................................................................................................49 Introduction ...........................................................................................................................50 Metholodogy ..........................................................................................................................50

Experimental set-up........................................................................................................................... 50 Sampling............................................................................................................................................ 51 Fungal analysis.................................................................................................................................. 52

Results and discussion ........................................................................................................52 SOLAR-DRYER TRIALS SEASON 1: 2003/04.............................................................................. 57

Summary ................................................................................................................................57 Introduction ...........................................................................................................................57 Objectives ..............................................................................................................................58 Methodology ..........................................................................................................................58

Drying method ................................................................................................................................... 58 Trial details ........................................................................................................................................ 58 Methodology ...................................................................................................................................... 59

Results and discussion ........................................................................................................60 Results .............................................................................................................................................. 60 Discussion ......................................................................................................................................... 61

Conclusion and recommendations .....................................................................................66 Conclusions ....................................................................................................................................... 66 Recommendations............................................................................................................................. 67

SOLAR DRYING TRIALS SEASON 2: 2004/05............................................................................. 70 Summary ................................................................................................................................70 Introduction ...........................................................................................................................70 Objectives ..............................................................................................................................71 Methodology ..........................................................................................................................71

Trials conducted ................................................................................................................................ 71 Trial implementation .......................................................................................................................... 71 Data collected.................................................................................................................................... 72

Results and discussion ........................................................................................................72

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Temperature and air relative humidity ............................................................................................... 72 Drying conditions............................................................................................................................... 74 Quality of green bean ........................................................................................................................ 75 Status of mould contamination in coffee beans................................................................................. 75 Coffee cup quality.............................................................................................................................. 76 Drying efficiencies ............................................................................................................................. 76

Conclusions and recommendations ................................................................................... 77 Conclusions....................................................................................................................................... 77 Recommendations ............................................................................................................................ 77

EFFECTS OF PROCESSING ALTERNATIVES AND DRYING METHODS ON DEVELOPMENT OF FUNGI IN COFFEE ...................................................................................................................... 79

Summary................................................................................................................................ 79 Introduction ........................................................................................................................... 79 Methodology.......................................................................................................................... 80

Experimental set-up .......................................................................................................................... 80 Mycological methods......................................................................................................................... 80

Results and discussion........................................................................................................ 81 Processing trials of 2003/4 ................................................................................................................ 81 Coffee bean infection ........................................................................................................................ 83 Processing trials of 2004/5 ................................................................................................................ 86

COFFEE QUALITY AND OCHRATOXIN A (OTA) FARMER SURVEY (2003/2004) ................... 88 Summary................................................................................................................................ 88 Introduction ........................................................................................................................... 88 Methodology.......................................................................................................................... 89 Results and discussion........................................................................................................ 89

1. Farm information ........................................................................................................................... 89 2. Harvesting and Production ............................................................................................................ 90 3. Coffee processing practice ............................................................................................................ 91 4. Summary of mycological analysis ................................................................................................. 93 5. Coffee storage............................................................................................................................... 95 6. Technical problems – farmers’ perspective ................................................................................... 95

Conclusions........................................................................................................................... 96 WHOLE FRESH CHERRY COFFEE AND MASHED FRESH CHERRY PROCESSING FARMER SURVEY (2004/2005) .................................................................................................................. 98

Summary................................................................................................................................ 98 Introduction ........................................................................................................................... 98 Methodology.......................................................................................................................... 98

Survey results and evaluation ........................................................................................................... 99 Discussion of cup quality evaluation................................................................................................ 102 Discussion of Mycology................................................................................................................... 103

Conclusions......................................................................................................................... 104 Recommendations .............................................................................................................. 104

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INTRODUCTION The FAO TCP/VIE/2903 project entitled, “Improvement of Coffee Quality and Prevention of Mould Formation and Ochratoxin A (OTA) Contamination of Coffee in Viet Nam,” was designed and implemented by the FAO Regional Office for Asia and the Pacific (FAO/RAP) with the assistance of the FAOR and staff of FAO in Viet Nam at the request of the GOV. The project was approved officially for funding and implementation by FAO late in December 2002, and implementation began officially in early 2003.

Overall objective Improved incomes and livelihoods of smallholder coffee producers in Viet Nam via production, processing, storage, transport and phytosanitary management interventions to improve coffee quality and its competitiveness, reduce losses and safeguard markets and coffee consumer’s health by reduction/elimination of Orchratoxin A contamination from moulds.

Counterparts from the Western Highlands Agro-Forestry Scientific and Technical Institute (WASI) in Buon Ma Thuot, Daklak province and CAFECONTROL (HCMC and Dak Lak) of the Ministry of Agriculture and Rural Development along with the Viet Nam Coffee and Cocoa Association (VICOFA), and the MARD Ba Vi Coffee Research Centres, and MARD Department of Science and Technology and provincial and district extension agencies, worked closely with FAO specialists and International and National Consultants to implement the project.

The project had many components including training, capacity building, surveys, research and development and building on R&D facilities for OTA detection and coffee quality improvement in both of the key agencies namely CAFECONTROL and WASI.

Key outputs 1. An improved microbiological and chemical analytical laboratory capacity, established at a

selected existing facility, in support of the National Programme on Ochratoxin (OTA) contamination of coffee. Staff trained in sampling, detection, identification and verification of OTA contamination in coffee.

2. A developed core of 20-25 trainers trained in the application of good food hygiene principles and HACCP to the coffee post-production chain.

3. Staff of the Coffee Standards Labs, WASI and Bavi Centres, buyers, roasters and key extension staff and select farmers trained in cup tasting and sensory analysis of coffee.

4. Field management recommendations and training materials developed for production of high quality mould free coffee. Staff of WASI, Bavi Centre, key Coffee Industry staff and key provincial and district extension staff and farmers trained in recommended field management production techniques.

5. Guidelines, training materials and demonstrations on harvesting, handling of fresh coffee cherries to maintain quality and avoid mould contamination. Staff of WASI, Bavi centre, key Coffee Industry staff and 200 key provincial and district extension staff and farmers and processors, trained in harvesting and handling of fresh coffee cherries.

6. An evaluation of coffee quality processed using dry processing, fully washed and semi-washed techniques at the WASI Centre in Buon Me Thout, which has such facilities. Staff of WASI, Bavi Centre key Coffee Industry staff and key provincial and district extension staff, buyers and farmers trained in appropriate processing methods.

7. Improved coffee drying techniques to overcome often rainy conditions at harvest and during processing. Staff of WASI, Bavi Centre key Coffee Industry staff and key provincial and district extension staff, buyers and farmers trained in these improved drying techniques.

8. Techniques for improving storage and minimising re-wetting of parchment, dry cherry and green beans in storage and during transport. Staff of WASI, Bavi Centre key Coffee

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Industry staff and key provincial and district Extension staff, farmers, buyers, roasters, exporters trained in these improved storage and transporting techniques.

9. National coffee quality and safety standards reviewed and up-dated in line with new recommended practices and existing international standards. A code of good practices for the coffee industry established and published. Staff of WASI, Bavi Centre key Coffee Industry staff and key provincial and district extension staff, farmers, buyers, roasters, exporters familiarised with these new practices and standards during training.

During the course of the project many new technologies, designed to improve coffee quality and reduce OTA contamination, were developed and tested with respect to coffee processing, drying and storage and coffee industry practices on-farm were surveyed. This report presents findings of these trials and surveys along with key additional information.

We apologise for some cases where data are missing or incomplete due to circumstances beyond our experimental control or late delivery of equipment items.

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TRIALS OF DOMESTIC AND IMPORTED WET COFFEE PROCESSING EQUIPMENT (SEASON 1:2003/04)

1Nguyen Van Thuong, Phan Thanh Binh **Keith Chapman

*** Anthony Marsh

Summary Wet coffee processing equipment trials conducted in 2003/04 found that the cost of “mashing” or “splitting” fresh coffee ranges from 5.2 VND/kg to 33.2 VND/kg (green bean equivalent), depending on size, quality and sophistication of mashing machine. This cost is quite small when compared to farm gate prices for green bean which range between 9000 to 14000 VND/kg. Mashing / Splitting can slightly increase the speed of drying but this process can also result in mould, quality and OTA problems as well as physical damage to the bean dried in the mash of skin and parchment.

The trials also found that coffee pulpers and demucilagers used with solar drying technology may be beneficial to the Viet Nam Coffee industry. Pulpers and demucilagers which pulp and separate skin and then remove the mucilage have been demonstrated to cost between 332.2 VND/kg and 170.1 VND/kg (green bean equivalent). While this is substantially more than the cost of mashing / splitting, there are substantial savings to be made in drying, as half of the total moisture of the cherry has been removed in the skin and the mucilage. Drying efficiency of each square meter of drying area can increase by over 100% after pulping and demucilaging. Added to this are the benefits of higher quality coffee and less chance of contamination from mould and OTA.

Introduction One of main reasons for poor coffee quality is mould and the possible OTA generation occurring during the drying stage of the coffee processing. Slow and uneven drying and re-wetting will result in mould generation and quality problems. In Viet Nam limited drying patio areas contribute to this slow drying, as coffee is stacked too deeply on drying patios.

The separation of the coffee pulp and mucilage layer from parchment coffee (both Arabica and Robusta) before drying will substantially reduce the time required for drying. In the past this was considered an expensive and impractical method, as suitable machinery was not available. New, small-scale machinery is now available and a study of this machinery has been performed.

Small-scale machinery is also available to mash coffee cherry leaving the skin mixed with the parchment but exposing the inner part of the coffee cherry and speeding drying. This technique is used in areas where there are large volumes of green cherry coffee harvested that cannot be pulped in the conventional manner. Mashing can also be described as “Splitting”, or “Crushing” depending on the actual action of the particular machine. A number of Vietnamese engineering companies have designed these low cost mashing machines.

Materials and methods The overall objective of these trials was to assess the effectiveness and economic efficiency of some coffee pulpers and mucilage remover combinations and coffee mashers to determine the most appropriate pulper and mucilage remover combination or mashers for Vietnamese farming households. Imported and domestic machines were compared.

1 *Postharvest Technology Department of Western Highlands Agro-forestry Scientific Technology Institute (WASI,) Boun Me Thout, Viet Nam **Industrial Crops Officer FAO, Bangkok ***International Coffee Consultant, Australia

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Description of two Pulper / Mucilage removal machines

• The ROBUSTA-600 of Penagos Company, Columbia • The LXT-1500 of Thong Nhat Mechanical Company, Viet Nam

Common specifications These are two synchronized pulper and mucilage removal systems consisting of siphon tank, loading bucket elevator, pulping system with two pulpers (primary pulper and re-passer), green cherry separator, mucilage-removal device, pulp and mucilage transferring screw, and pressure pump.

Descriptions The Columbian Penagos Robusta-600 machine has a pre-cleaner with rotary screen for separating foreign matter before cherries go to a siphon tank, a water filter and a feed regulator for cherry from hopper to the pre-cleaner and pulper. This regulator also controls the flow of parchment coffee to the mucilage remover. The Vietnamese Thong Nhat LXT-1500 machine has a green cherry separator (to increase pulping efficiency of the pulper). The first stage pulper has a rubber breastplate. The pulping and demucilaging system is non-synchronous so it is quite difficult to operate. It requires more labour to ensure good quality of parchment output. The siphon tank has a water pump with a high capacity and as a result some good cherries are discharged to waste.

Penagos Robusta-600

Thong Nhat LXT-1500

Descriptions of three coffee mashers

• VINACAFE Company in NhaTrang, Viet Nam (VN Masher) • Le Trung Chau Mechanical Company (LTC Masher) • Thong Nhat Mechanical Company (TN masher)

General comments No water is required for any of the mashers. All three mashers are made in Viet Nam.

Descriptions The VINACAFE Masher (VN Masher) uses two abrasive vertical plates, one fixed and the other rotating. Cherry is split as they pass into the slit between two plates. The distance between the plates is easily adjusted to control the amount of cherry splitting required.

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The Thong Nhat Masher (TN Masher) uses a cylindrical horizontal drum fixed with raised bars. When it rotates it crushes coffee cherry into a rough metal breastplate. The distance between the pulping drum and breastplate can be easily adjusted to control the level of crushing.

The Le Trung Chau Masher (LTC Masher) uses a horizontal rotor and stator. The stator is a slotted cylinder. The rotor is a spiral grooved drum inside the slotted cylinder. The rotor presses coffee cherries onto the stator splitting the coffee cherry and pressing both parchment and mashed skins through the slotted holes of stator.

Mashed coffee

Le Trung Chau Masher

VINACAFE Masher

Thong Nhat Masher

Methodology • All the machines were installed in the Postharvest Research Section at WASI (Western

Highlands Agro-forestry Scientific and Technology Institute, Boun Me Thout, Viet Nam). • Individual machines were adjusted until they operated well. • Robusta coffee was harvested from WASI coffee farm for the trials. • 1000 kg of Robusta coffee was processed through each of the two pulper-mucilage remover

machines for each test. Each machine was tested two times. • 500 kg of Robusta coffee was processed through each of the mashers for each test. Each

machine was tested 3 times. • Coffee cherry quality for trials represented normal coffee quality of small farm practices in

the region. The trials were carried out during the harvesting season of 2003/04.

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Specific data collected from the trials • Water consumption was measured with a water meter. • Electricity consumption was measured with an electricity meter. • Quality of coffee was assessed in percent weight of unripe, ripe, overripe cherries and

foreign matter. • Equipment capacity was measured in throughput of cherry, kg/hr. • Quality of parchment coffee after pulping was assessed by percent weight of unpulped

cherries, parchment-peeled beans, broken beans and parchment coffee that the mucilage layer had not been removed.

• Pulp efficiency was assessed as percent by weight of pulped coffee /mass of products at the outlets of the machine.

• Mucilage removal efficiency was assessed as the weight of mucilage removed from pulped parchment coffee beans (1000 parchment beans counted and weighed before and after demucilaging). The result was expressed as a percent of original weight.

• An assessment of cost-effectiveness of each machine was made based on the following criteria: • Purchase and depreciation cost • Operational cost • Maintenance cost

Results and discussion Quality of cherry material The quality of coffee used for the machine trials is presented in Table 1.

Table 1. Quality of Robusta cherry used in each test run

Rep. No

Machine %w/w foreign matter

% w/w overripe cherry

% w/w dried cherry

% w/w unripe cherries

% w/w ripe cherries

1 Robusta-600 1.25 9.8 3.0 20.5 65.6 2 Robusta-600 3.3 4.3 3.3 18.3 70.9 1 LXT-1500 1.8 3.0 3.7 13.0 78.4 2 LXT-1500 1.8 6.9 3.4 23.4 64.7

R1 1st Masher test 2.9 14.8 4.2 20.7 57.4 R2 2ndMasher test 3.3 4.3 3.3 18.3 70.9 R3 3rd Masher test 1.1 2.7 1.5 62.3 32.4

Cherry used for processing had a high proportion of green cherries (between 13% and 23%) for two of the pulper-mucilage removal machines. The cherry for the masher test had a very high proportion of green cherry (62.3%). High green cherry rates are very typical in Viet Nam coffee farms, as coffee is strip picked only once or twice per season. The bean is mature, but the coffee cherry has not coloured.

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Major specifications of the processing machines Table 2 shows that the Robusta-600 consumed more electricity per unit of cherry than the LXT-1500 (13.6 Kw/MT of fresh cherry compared to 7.1 Kw/MT of cherry). However the Robusta-600 consumed less water than the LXT-1500 (1.2 m3/MT compared to 4.08 m3/MT). Although LXT-1500 has twice the capacity of the Robusta 600 the similar amount of labour is needed for processing 1 MT of cherry (0.5 md/MT compared to 0.43 md/MT) because different parts of the LXT-1500 system are not synchronized and have to be operated by hand.

Table 2. Specifications of the processing machines

Machines Cost delivered to WASI (USD)

Capacity of cherry processed kg/hour

Electric power consumption

Kw/MT of cherry

Labour No of man days /

MT of cherry

Water consumption m3/ MT of fresh

cherries Robusta-600 7000 576 13.6 0.5 1.2 LXT-1500 4300 1240 7.1 0.43 4.08

VN masher 200 754 1.99 0.18 0 TN masher 150 3648 0.41 0.04 0 LTC masher 300 521 2.88 0.26 0 There was a wide range in processing capacities, electricity consumption and labour costs in the mashers. The TN masher had the lowest power consumption/MT and the lowest labour cost/MT.

Machine performance Pulper-mucilage removing machines Table 3. Performance of two pulping and demucilaging machines

Parchment outputs from Pulper-Mucilage removing machines

Criteria Robusta-600 LXT-1500 Percent (by weight) ripe cherries removed by siphon tank before pulping (Floaters) 7.2 7.1 Percent(by weight) intact cherries after pulping and before demucilaging (Unpulped green cherry)

8.2 9.1

Pulping efficiency (Percent) 91.8 90.9 Percent (by weight) of skin adhering to wet parchment in demucilaged parchment output.

6.3 8.1

Percent (by weight) of skin (not adhering to parchment) in demucilaged parchment output.

2.55 1.95

Percent (by weight) nipped or damaged parchment in demucilaged output. 7.25 7.8 Percent (by weight) reduction of parchment due to mucilage removal. (Weight of 1000 parchment before and after mucilage removal) (Note: 100% mucilage removal was calculated to be 16.2%).

14.6 8.5

Percent parchment coffee with mucilage intact in output. (1000 parchment beans selected by eye)

8.5 48.3

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Performance of two pulping and demucilaging machines Analysis of the performance outcomes of the two machines in Table 3 shows that the proportion of cherry, pulp, non-pulped beans, and parchment removed beans and rate of removed/ discharged coffee from the two machines are not significantly different. However, there is a large difference in parchment weight reduction due to mucilage removal (14.6% from Robusta-600 and 8.5% from LXT-1500 machine). The calculated mucilage removal efficiency based on a weight reduction of 16.2% for 100% removal of mucilage gave 91.5% from Robusta-600, compared to 51.7% from LXT-1500 machine. This was further reinforced by the visual assessment of the demucilaging efficiency, which gave 8.5% for Robusta-600 and 48.3% for the LXT-1500 with mucilage still intact. The reason for poor demucilaging of the LXT-1500 was that the pulping speed depended on hand feeding and the design of the demucilager, which made it difficult to control the parchment coffee flow into the mucilage remover. The pulping efficiency of the two machines was similar at 91.8% for the Robusta-600 and 90.9% for the LXT-1500. Table 4. Performance of coffee mashers

Repetition

Machine

Proportion of unmashed whole cherry (% w/w)

Proportion of bean with parchment removed (%

w/w)

Proportion of machine damaged bean (%w/w)

VN masher 5.7 7.5 2.4 TN masher 6.3 14.9 2.2

R1

LTC masher 4.2 1.3 0.6 VN masher 7.2 8.4 2 TN masher 7.9 12.5 2.5

R2

LTC masher 5.4 1.5 0.6 VN masher 8.4 22.5 2.6 TN masher 3.4 16.3 3.0

R3

LTC masher 5.0 5.4 0.8 VN masher 7.1 12.8 2.3 TN masher 5.9 14.6 2.6

Av.

LTC masher 4.9 2.7 0.7 The three coffee mashers were simultaneously operated with three different types of coffee (from three harvesting times). Output product data after mashing are presented in Table 4. The result shows that the TLC Masher produced the best quality product, with only 0.7% damaged beans, 2.7% of beans with parchment removed and only 4.9% of non-pulped cherries on average. The LTC Masher produced good results (5.0% of cherries, 5.4% of beans without parchment and 0.8% damaged beans) from R3, which had high proportion of green cherries (62.3%). For this same R3, the VN masher produced a far less desirable product (8.4% cherries, 22.5% beans with parchment removed 2.6% damaged beans). The TN masher also produced a poor product for R3 of 16.3% of beans without parchment and 3% of damaged beans.

Processing costs The results in Table 5 show that although the LXT-1500 consumed three times more water than Robusta-600, the total cost/kg of bean of the LXT-1500 is far lower than that of Robusta-600 (332.3 VND/kg compared to 170.1 VND/kg). This is due to a relatively large capacity of the machine (twice Robusta 600) plus low purchase price of the Vietnamese machine, lower maintenance cost per unit and lower consumption of electricity.

The larger the masher capacity, the lower the overall processing cost/kg. The TN masher costs only 5.2 VND/kg while the LTC masher was 33.2 VND/kg, 6 times higher and 22.6 VND/kg of bean for VN Masher. However despite the higher cost of the LTC masher with a capacity of 500 kg to 1000kg/h, it produced a high quality product and is thus the most appropriate for smallholders.

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Table 5. Processing costs of machines Machines

Item Unit cost *** Robusta-600 LXT-1500 VN masher TN masher LTC masher

Power VND/kg of clean bean

75.1 39.2 0.5 0.1 0.8

Water VND/kg of clean bean

11 37.5 0 0 0

Man-day VND/kg of clean bean

57.5 49.5 20.7 4.6 29.9

Depreciation * VND/kg of clean bean

188.6 43.8 1.4 0.5 2.5

Maintenance ** VND/kg of clean bean

0.118 0.055 0.015 0.003 0.022

Total cost (VND/kg of bean) 332.3 170.1 22.6 5.2 33.2 * Depreciation is calculated as the cost of the machine averaged over 15 years, two month/year, 8 working hours/day. ** Maintenance: for pulper: 6man-day/pulper/year. For masher: 1 man-day/masher/year. *** Unit Cost is the cost output from each machine (wet cleaned parchment or wet mashed coffee converted to a clean dry (12%) Green Bean equivalent, for ease of comparison.

Conclusions and recommendations Conclusions on the two pulper-mucilage machines • The Penagos Robusta-600 is easier to operate, requires less labour to feed coffee and the

siphon tank operates better. • Robusta-600 system consumes less water (1.2m3/ton of cherry) than LXT-1500 system

(4.03m3/MT of cherry). • Most performance criteria for both machines is very similar, but the Robusta-600 has much

better demucilaging performance. • Pulping efficiencies are similar. • Mucilage removal efficiency of Robusta-600 is far higher than that of LXT-1500 at 91.5%

compared to 51.7%. • Cost/kg of clean bean equivalent for the LXT-1500 system is170.1 VND/kg which half the

cost of the Robusta-600 at 332.3 VND/kg. This is largely due to the high capital cost of the Robusta-600.

Conclusions on the three masher machines • The three mashers tested have three completely different operation systems, which produce

different qualities of mashed coffee. • The LTC masher gave the best quality of output with only 4.9% of non-pulped cherries,

2.7% of beans without parchment and 0.7% of damaged beans over all replications. • The VN masher gave a medium quality of products with 7.1% of non-pulped cherries,

12.8% of beans without parchment and 2.3% of damaged beans over all replications. • The masher of TN masher gave the poorest quality of output with 5.9% of non-pulped

cherries, 14.6% of beans without parchment and 2.6% of damaged beans.

Recommendations • The Penagos Robusta-600 machine is the preferred machine tested for producing

demucilaged Robusta coffee, as it has good demucilaging capabilities.

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• Further comparisons with other pulper/demucilaging machines with the same capacity should be carried out to determine advantages and disadvantages of all available machines. (See the season 2 2004/05 report comparing 4 pulping demucilaging machines)

• It is recommended that Thong Nhat Mechanical Company improve the following parts of the LXT-1500: • Siphon tank should be redesigned to make it correspond to the capacity of the pulper. • A regulator for inlet coffee should be added on the material-feeding funnel. • The mucilage remover should be re-designed to reduce water usage and to improve

mucilage removal efficiency. • The cherry and parchment feeder on the green separating screen should be redesigned to

improve performance. • Machines made by Thong Nhat Mechanical Company and VINACAFE Company for

mashing coffee are not recommended for use by coffee farmers as they cause a large amount of damage to the coffee beans.

• The Le Trung Chau masher can possibly be used by smallholders in certain circumstances if drying conditions are good to speed up drying. (Note: If drying conditions are poor, massive mould development is possible and coffee quality is severely degraded.) More research should be carried out to improve the machine to remove pulp after mashing for more convenient drying of coffee. (Note: A new LTC prototype machine was tested in Season 2, 2004/05 coffee processing report).

Names and addresses of machinery suppliers PENAGOS COMPANY HNOS & CIA LTDA Calle 28, No. 20 – 80 Bucaramanga Columbia

Ph: 57 7 630 1600/63 2794 Fax: 57 7 6302795/6469321

THONG NHAT MECHANICAL COMPANY 49 Nguyen Tat Thanh Buon Me Thout, Daklak Province Viet Nam

Tel: 050 952290 – 95 1960 Email: martnc@vol.vnn.vn

VINACAFE ENGINEERING ENTERPRISE 05 Truong Son Street Binh Tan Industrial Zone Nha Trang City, Khanh Hoa Province Viet Nam

Tel: 058 883193 Fax: 058 883151 Email: ckvinacafe@dng.vnn.vn

LE TRUNG CHAU 114/9 Hung Vuong Boun Me Thout, Daklak Province Daklak Viet Nam

Tel: 050 852503

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TRIALS ON DOMESTIC AND IMPORTED WET COFFEE PROCESSING EQUIPMENT REPORT 1:

ARABICA COFFEE (SEASON 2: 2004/05) 2*Nguyen Van Thuong, Phan Thanh Binh

**Keith Chapman ***Anthony Marsh

Summary Trials were conducted to compare the efficiency of four Arabica coffee pulping/demucilaging machines. It was found that the four machines tested have smaller capacities of fresh cherry kg/hour; the VINACAFE (523 kg/hr), Pinhalense (756 kg/hr) and the Penagos (587 kg/hr) machines, compared to the LXT-1500 (1850 kg/hr).

• All four machines had good pulping efficiencies (all above 93%) and mucilage removal performance (all between 14% and 17%). The UCBE 500M machine consumed the least water at 1.4m3/MT of cherry compared to the Pinhalense (2.2m3/ MT), the VINACAFE (2.95m3/ MT) and the LXT-1500 (3.46m3 /MT).

• All machines gave similar bean quality, with the LXT-1500 giving the lowest proportion of the machine-damaged beans at 0.72%.

• Direct processing cost/kg of green bean for the VINACAFE machine was the lowest at 127.3 VND/kg with LXT-1500 second at 159.8 VND/kg, the next was the Penagos at 250.5 VND/g and the Pinhalense was highest at 352.9 VND/kg bean. The VINACAFE is the simplest machine to operate followed by the Pinhalense, the Penagos while the LXT-1500 is the most complex.

• The VINACAFE machine has acceptable performance in terms of pulping efficiency and mucilage removal. It is the simplest machine and it has the lowest cost per kilo processing cost. This machine needs further trials in practical on farm situations.

• Even though the VINACAFE machine was a simple prototype machine, it compared very favourably with the three commercial machines and had the lowest cost per kilo processing cost. The VINACAFE had acceptable performance in terms of pulping efficiency and mucilage removal. This machine is recommended as the most appropriate for farm use, but further trials in practical on-farm situations are required.

Introduction One of main reasons for poor coffee quality is the possible mould production and OTA generation, which can occur during the drying stage of the coffee processing. Slow and uneven drying or rewetting may result in mould generation and quality problems. In Viet Nam, limited drying patio areas contribute to this slow drying as coffee is stacked too deeply on drying patios.

The separation of coffee pulp and mucilage layer from parchment coffee before drying will substantially reduce the time required for drying. In the past this was considered an expensive and impractical method as suitable machinery was not available. New, small-scale machinery is now available and a study of the cost-effectiveness of this machinery has been performed.

Small-scale machinery is also available to mash coffee cherry leaving the skin and mixed with the parchment but exposing the inner part of the coffee cherry to the atmosphere and to speed 2 * Postharvest Technology Department, Western Highlands Agro-Forestry Scientific Technology Institute (WASI), Buon Me Thout, Viet Nam ** Industrial Crops Officer, FAO Bangkok *** International Coffee Consultant

18

up drying. This technique is used in areas where there are large volumes of green cherry coffee harvested that cannot be pulped in the conventional manner. Mashing can also be described as “Splitting”, or “Crushing” depending on the actual action of the particular machine.

Objectives A trial was conducted for four of wet Arabica coffee processing machines to assess their effectiveness and efficiency. The trial was conducted over the 2004/05 coffee seasons.

Materials and methods Pulper/demucilager machines tested for processing of Arabica coffee are:

• UCBE 500 M system of Penagos Company, Columbia • Eco-0SVX system from Pinhalense Company, Brazil. • LXT-1500 system from Thong Nhat Mechanical Company, Viet Nam. • Pulper and demucilager combination from VINACAFE Company, Viet Nam.

Individual machine descriptions The Penagos UCBE 500 M: Coffee feeds directly from the hopper into a vertical axis pulping drum. The machine has a rotating screen to sort unpulped green bean with parchment then feeding directly into a vertical demucilager. A screw conveyor removes skin and mucilage. The machine uses a single electric motor with a system of belts to drive the various components. The machine is complex with many moving parts compared to the others trialed.

The Pinhalense ECO-OSVX: Coffee is fed into the green cherry sorter at the top of the machine. The green cherry separator is a screw shaft in a horizontal slotted cage. Coffee passing through the cherry separator feeds vertically into a vertical rotating drum pulper with 3 pulping breasts. Pulped coffee then feeds into a vertical demucilager.

Penagos UCBE 500

Pinhalense ECO-OSVX The Thong Nhat LXT-1500: Green cherry is separated in a floatation tank to increase pulping efficiency of the pulper. The first stage pulper uses a rubber breast plate. Different parts of the system are non-synchronous and require more labour to get a good flow of coffee. The siphon tank has a high volume water pump and as a consequence a great amount of good coffee was discharged to waste. The machine also has a bucket elevator to feed cherry coffee to the pulper.

The VINACAFE Pulper Demucilager: This machine is simple combination of 2 separate machines. There is no green cherry sorting. Two standard drum pullers in series are driven by 1

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motor to maximize pulping of green cherry. The pulped coffee feeds directly into the vertical demucilager. The machine was not installed in time for this trial in Viet Nam, so data from FAO trials in Myanmar are referred to in this report.

Thong Nhat LXT-1500

VINACAFE Pulper Demucilager

Coffee used for processing trial Quality of Arabica coffee material for processing is shown in Table 1. The coffee had relatively high proportion of dried and overripe cherries (Overripe: between 12.7 and 18.2%; Dried cherry: between 8.9 and 12.3%). This high proportion of dry and over ripe coffee affected the pulping process and final bean quality.

Table 1. Arabica cherry coffee quality used for each trial replication (% by weight)

Trial Repetition

% green/unripe cherry

% ripe cherry

% overripe cherry

% dried cherry

% foreign matter

% damaged cherry

1 8.7 62.5 14.2 12 1.4 1.2 2 11 64.4 12.7 8.9 1.9 1.1 3 9.1 58.5 18.2 10.8 1.7 1.7

Methodology Trial implementation The processing trials were carried out with the above-mentioned equipment using Arabica coffee from the WASI farm. 1500kg of cherry coffee was used for each machine combination. The trial was carried out during the 2004 coffee harvest.

Specific outputs and data collected • Water consumption of each machine was measured with a water meter. • Electric consumption of each machine was measured with an electricity meter in Kw/hr. • Quality of coffee used in each trial was assessed as percent by weight of unripe, ripe,

overripe cherries and foreign matter. • Machine capacity was measured as weight of cherry throughputs in kg/hr. • Quality of parchment coffee after pulping was measured as a percent by weight of unpulped

cherries, parchment-peeled beans, broken beans and parchment coffee that the mucilage layer had not been removed.

• Pulping efficiency was measured as a percent by weight of pulped and unpulped parchment coffee.

• Mucilage removal efficiency was assessed as the weight of mucilage removed from pulped parchment coffee beans by weighing1000 parchment beans before and after demucilaging. The result was expressed as a percent of original weight.

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• Mucilage removal efficiency as also measured as a proportion of parchment with mucilage removed by visual assessment.

• Assessment of physical and cup quality.

Results and discussion Key technical specifications of Arabica coffee processing equipment Table 2 indicates the capacity in kg/hr, the electricity usage and labour requirement for each machine needed to process one MT of fresh cherry. The LXT-1500 machine consumed the highest amount of water (3.46 m3/ MT) and the UCBE 500M machine consumed the lowest (1.4 m3/MT of cherry. LXT-1500 has the highest capacity of 1850 kg of cherry/hour.

Table 2. Some technical specifications of arabica coffee processing equipment

Machine Purchase cost USD$

Capacity kg/hour

Electricity consumed kw/MT of cherry

Man-day/ MT of cherry

Water consumed m3/MT of cherry

UCBE 500M 3230 587 14 0.43 1.4 LXT-1500 4300 1850 7.1 0.43 3.46 VINACAFE * 650 523 5.57 0.34 2.95 Pinhalense 7158 756 9.92 0.5 2.2 *Data also collected in FAO trials in Myanmar

Pulping and mucilage removal performance and quality dried coffee Table 3 presents results on pulping and mucilage removal performance of the four different Arabica processing machines. All four machines had good pulping efficiencies (all above 93%) and mucilage removal performance (all between 14% to17%).

Table 3. Arabica pulping and mucilage removal performance

Criteria UCBE 500 M

Pinhalense LXT-1500

VINACAFE*

Percent whole cherries passing through pulper without being pulped 4.5 3.3 3.4 6.5 Percent Pulping efficiency 95.5 96.7 96.1 93.5 Percent of loss (beans discharged along with pulp) 0.13 0.15 0.1 0.6 Percent (by weight) skin being delivered with pulped parchment after pulping

4.7 4.1 2.7 6.5

Percent (by weight) parchment nipped or parchment skin removed in demucilager output.

7.3 5.6 2.3 3.4

Percent (by weight) reduction of parchment weight due to mucilage removal. (Weight of 1000 parchment beans before and after mucilage removal) (Note: 100% mucilage removal was calculated to be 19%).

15.2 17.1 14.6 15.4

Percent Mucilage Removal Efficiency 80 90 76 81 Percent (by weight) parchment coffee with some mucilage intact. (visual count – 1000 beans)

4.5 2.9 10.8 3.5

*Data also collected in FAO trials in Myanmar.

Physical quality of dry coffee The results in Table 4 show that generally, wet processed coffee gave better colour and quality than dry processed coffee. This is partly because classification occurred during processing and bad cherries have been rejected when going through siphon tank. Green cherry grading and floatation by the LXT 500 and Pinhalense also gave a better output of quality.

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Table 4. Bean quality analysis

Bean quality Machine/machine combination

Bean colour Black beans (%)

Machine damaged beans (%)

Poor colour beans (%)

LXT-1500 Typical blue colour of Arabica coffee

0.39 0.72 1.17

Pinhalense Typical blue colour of Arabica coffee

0.43 1.4 1.56

UCBE 500M Typical blue colour of Arabica coffee

0.52 2.16 1.26

VINACAFE A bit dark due to many straw-coloured beans

0.66 3.37 2.55

Control sample (Dry processed cherry)

Dark with many straw-coloured and brownish beans

1.15 0 3.61

Cup quality of dry coffee Table 5 presents the taste results for coffee produced by the different machines. Taste results showed that products of Penagos UCBE 500M and Pinhalense machines were good. However, the Pinhalense machine produced was the best quality as a result of not using recycled water. Products from the LXT-1500 and VINACAFE machines were considered fair to good. The control sample seemed to be over-fermented (due to high amount of over-ripe cherries) and during the long drying period the fermented aroma has permeated into the green bean.

Table 5. Quality assessment of Arabica green bean

Processing equipment

Aroma Flavour General evaluation

UCBE 500 M Strong, average fragrant, clean Balanced, clean Good Pinhalense Strong, average fragrant, clean Balanced, pure, medium acidy Good LXT-1500 Strong, average fragrant, one cup

with normal flavour Balanced, one cup had taint flavour, a little acidy

Fair

VINACAFE Strong, fragrant, clean Balanced, medium acidity Fair Control sample (dry processed beans)

Coffee aroma mixed with fermented smell

Over-fermented flavour and fruity Poor

Direct costs to process/produce 1kg of green bean coffee Direct costs for 1kg of bean of Pinhalense machine are highest at 352 VND/kg, followed by the UCBE machine. These two imported machines both have low capacity (500 kg of cherry/hour), high purchase cost and a high labour cost. Processing cost of LXT-1500 machine is lower at 159.8 VND/kg of bean due to high capacity and low capital cost per 1kg of bean. The lowest overall direct cost was achieved with the VINACAFE machine at 127.3 VND/kg. Table 6 below presents direct cost for all four machines.

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Table 6. Direct cost for processing fresh cherry to clean wet Arabica parchment (Costs given as green bean 12% M.C. equivalents)

Costs (VND / kg of green bean equivalent) Machine Water Electricity Labour Capital cost/

depreciation **

Maintenance ***

Total unit cost ****

VND/kg green bean equivalent

Pinhalense 27.7 75 96.6 152.1 1.5 352.9 LXT-1500 51.7 53.7 27.6 26 0.8 159.8 UCBE 17.6 90.3 69 71.5 2.1 250.5 VINACAFE* 32.3 43.4 27.6 23 1.0 127.3

*Data also collected in FAO trials in Myanmar. ** Depreciation is calculated as the cost of the machine averaged over 15 years, two month/year, 8 working hours/day. *** Maintenance: for pulper demucilagers: 6 man-day/pulper/year. **** Unit Cost is the cost output from each machine (wet cleaned parchment converted to a Clean Dry (12%) Green Bean equivalent for ease of comparison. Unit Costs of processing fresh cherry are converted to dry green bean equivalents at the ratio of 6.5 kg of fresh cherry to produce 1 kg of dry green bean at 12% moisture.

Conclusions and recommendations Conclusions The VINACAFE, Pinhalense Eco-0SVX and the Penagos UCBE 500M machines all have smaller capacities of 523, 756 and 587 kg/hour fresh cherry respectively compared to 1850 kg/hour of LXT-1500 machine.

All four machines have good pulping efficiencies (all above 93%) and mucilage removal performance (all between 14% to 17% (19% of fresh parchment weight was mucilage) Mucilage removal efficiency for each machine was calculated as: 90% for the Pinhalense, 80% for the Penagos, 81% for the VINACAFE and 76% for the LXT-1500.

The UCBE 500M machine consumed the least water at 1.4m3/MT of cherry compared to 2.2 m3/MT for the Pinhalense, 2.95 m3/MT for the VINACAFE and 3.46 m3/MT for the LXT-1500).

All machines gave similar bean quality. The LXT-1500 had the lowest proportion of the machine damaged beans at 0.72%.

Direct cost/kg of green bean for the VINACAFE machine was the lowest at 127.3 VND/kg, the LXT-1500 system was second at 159.8 VND/kg of bean, the next was the Penagos at 250.5 VD/g and the Pinhalense was highest at 352.9 VND/kg bean.

The VINACAFE is the simplest machine to operate followed by the Pinhalense, the Penagos while the LXT-1500 is the most complex.

Recommendations The LXT-1500 machine can be used for processing Arabica coffee. The water supply to pulper and demucilager should be redesigned to save water.

A siphon tank and feed elevator should be designed for the Pinhalense machine to save operational labour.

The VINACAFE machine appears to have acceptable performance in terms of pulping efficiency and mucilage removal. It is the simplest machine and it has the lowest cost / kg processing cost. This machine needs further trialing in practical on-farm situations.

Names and addresses of machinery suppliers

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PENAGOS COMPANY HNOS & CIA LTDA Calle 28, No. 20 – 80 Bucaramanga Columbia

Ph: 57 7 630 1600/63 2794 Fax: 57 7 6302795/6469321

THONG NHAT MECHANICAL COMPANY 49 Nguyen Tat Thanh Buon Me Thout, Daklak Province Viet Nam

Tel: 050 952290 – 95 1960 Email: martnc@vol.vnn.vn

VINACAFE ENGINEERING ENTERPRISE 05 Truong Son Street Binh Tan Industrial Zone Nha Trang City, Khanh Hoa Province Viet Nam Tel: 058 883193 Fax: 058 883151 Email: ckvinacafe@dng.vnn.vn

LE TRUNG CHAU 114/9 Hung Vuong Boun Me Thout, Daklak Province Daklak Viet Nam Tel: 050 852503

PINHALENSE S/A MAQUINAS AGRICOLAS Rua Honorio Soares 80 Esp. Tso. Pinhal-SP Brazil CEP 13.990-000

Tel: 55-19 3651 1079 Fax: 55-19 3651 3602 Email: peamarketing@peamarketing.com.br

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TRIALS ON DOMESTIC AND IMPORTED WET COFFEE PROCESSING EQUIPMENT REPORT 2:

ROBUSTA COFFEE (SEASON 2: 2004/05) 3*Nguyen Van Thuong, Phan Thanh Binh

**Keith Chapman ***Anthony Marsh

Summary Trials were conducted to compare the efficiency six Robusta pulping and demucilaging machines. Three commercial Robusta Pulping/Demucilaging systems (Pinhalense, Robusta 600 and LXT-1500) were tested along with 3 prototype machines (Le Trung Chau, Thong Nhat and VINACAFE). The VINACAFE machine was also tested in Thailand using similar trial protocols and that data is used in this report.

• Pulping efficiency of the 3 larger commercial machines was all above 95%, primarily as they used green cherry sorting technologies.

• The Prototype Le Trung Chau machined used mashing technology and had good pulping efficiency at 96.1%. The prototype Thong Nhat used normal pulping and had low efficiency at 88.8%. The VINACAFE had slightly lower pulping efficiency as it used a simple double pulper with no green cherry sorting.

• Mucilage remove efficiency for each machine was calculated at 84% for the Pinhalense, 78.3% for the Penagos, 73.3% for the VINACAFE and 51.1% for the LXT-1500.

• Water consumption of LXT-1500 is highest at 4.1m3/MT of cherry and the Robusta 600 is lowest at 1.42m3/MT of cherry.

• Bean damage was similar for all machines with LTX 1500 the lowest at 0.67% and highest in Robusta 600 at 1.45%.

• Even though the VINACAFE machine was a simple prototype machine it compares very favourably with the 3 commercial machines tested and had the lowest cost/kg processing cost. The VINACAFE had acceptable performance in terms of pulping efficiency and mucilage removal. This machine is recommended as the most appropriate for farm use but further trials in practical on-farm situations is required.

Introduction Slow and uneven coffee drying and re-wetting may result in mould generation and quality problems. In Viet Nam, limited drying patio areas contribute to this slow drying as coffee is stacked too deeply on drying patios.

The separation of coffee pulp and mucilage layer from parchment coffee (both Arabica and Robusta) before drying will substantially reduce the time required for drying. In the past this was considered an expensive and impractical method, as suitable machinery was not available. New, small-scale machinery is now available and a study of the cost-effectiveness of this machinery has been performed.

Small-scale machinery is also available to mash coffee cherry leaving the skin and mixed with the parchment but exposing the inner part of the coffee cherry to the atmosphere and speeding drying. This technique is used in areas where there are large volumes of green cherry coffee

3 * Postharvest Technology Department of Western Highlands Agro-forestry Scientific Technology Institute, (WASI) Boun Me Thout, Viet Nam. ** Industrial Crops Officer, FAO Bangkok *** International Coffee Consultant

25

harvested that cannot be pulped in the conventional manner. Mashing can also be described as “Splitting”, or “Crushing” depending on the actual action of the particular machine.

Objectives Trials were conducted for a range of wet coffee processing equipment (pulper and demucilager combination systems and coffee mashers). The trials were conducted for Robusta coffee over the 2004/05.

Material and methods Machines tested Six pulper demucilager machines were tested for processing of Robusta coffee.

• ECO-0SVX pulper/demucilager system from Pinhalense Company, Brazil. • ROBUSTA 600 pulper/demucilager system of Penagos Company, Columbia. • LXT-1500 pulper/demucilager system of Thong Nhat Company, Viet Nam. • Prototype Masher/Pulper of Thong Nhat,Viet Nam. • Prototype masher/demucilager of Le Trung Chau Company, Viet Nam. • Pulper/demucilager combination of VINACAFE Company, Viet Nam.

Description of equipment The Penagos Robusta-600. Coffee feeds into a pre-cleaner with rotary screen for separating foreign matter before cherries go to a siphon tank. A water filter pipe and a feed regulator for cherry from hopper to the pre-cleaner and pulper. This regulator also controls the flow of parchment coffee to the mucilage remover.

The Thong Nhat (TN) LXT-1500. Green cherry is separated in a floatation tank to increase pulping efficiency of the pulper. The first stage pulper uses a rubber breastplate. Different parts of the system are non-synchronous and require more labour to get a good flow of coffee. The siphon tank has a high volume water pump and as a consequence a great amount of good coffee was discharged to waste. The machine also has a bucket elevator to feed cherry coffee to the pulper.

Robusta-600

Thong Nhat LXT-1500

The Pinhalense ECO-OSVX. Coffee is fed into the green cherry sorter at the top of the machine. The green cherry separator is a screw shaft in a horizontal slotted cage. Coffee passing through the cherry separator feeds vertically into a vertical rotating drum pulper with 3 pulping breasts. Pulped coffee feeds into a vertical demucilager.

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Prototype Le Trung Chau (LTC) Masher/demucilage. This machine has a slotted screen screw masher. The masher consumes a lot of water. Feed from the mashing cage to demucilager section often resulted in clogging during operation.

Pinhalense ECO-OSVX

Le Trung Chau Masher/Demucilager Prototype Thong Nhat (TN) Masher / Pulper. This is a masher mounted over a drum pulper. This machine attempts to separate the mashed skin from parchment using a pulper. It does not demucilage the parchment. The two units (masher and pulper) are unequal in capacity and result in difficult control of material feeding into the machine. The poor manufacturing tolerances between the drum and breast plate made it difficult to adjust the pulping to a required standard level.

The VINACAFE (VN) Pulper Demucilager: This simple combination of 2 separate machines, a pulper and a demucilager. There is no green cherry sorting. Two standard drum pulpers in series are driven by 1 motor to maximize pulping of green cherry. The pulped coffee feeds directly into the vertical demucilager. The demucilaging unit was not installed in time for this trial in Viet Nam, so data from a similar FAO trial in Thailand is referenced in this report.

Thong Nhat prototype masher/ pulper

VINACAFE pulper demucilager

27

Methodology Trial implementation During the 2004 coffee harvest, processing trials were carried out with the above-mentioned equipment using Robusta coffee from the WASI farm at Boun Me Thout, Viet Nam. Each machine combination used 1500 kg of cherry coffee.

Specific outputs and data collected • Water consumption of each machine was measured with a water meter. • Electric consumption of each machine was measured with an electricity meter in Kw/hour. • Quality of coffee used in each trial was assessed as percent by weight of unripe, ripe,

overripe cherries and foreign matter. • Machine capacity was measured as weight of cherry throughputs in kg/hr. • Quality of parchment coffee after pulping was measured as a percent by weight of unpulped

cherries, parchment-peeled beans, broken beans and parchment coffee that the mucilager had not removed.

• Pulping efficiency was measured as a percent by weight of pulped and unpulped coffee. • Mucilage removal efficiency was assessed as the weight of mucilage removed from pulped

parchment coffee beans, by weighing1000 parchment beans before and after demucilaging. The result was expressed as a percent of original weight. Mucilage removal efficiency as also measured as a proportion of parchment with mucilage removed by visual assessment.

• Quality assessment of the dried coffee.

Quality of Robusta cherry used in the trials

Table 1. Result of analysis of Robusta coffee cherry used in the trials

Trial repetitions

% unripe cherry

% ripe cherry

% over-ripe cherry

% dried cherry

% foreign matter

% damaged cherry

1 5.6 81.2 4.9 4.3 1.2 2.8 2 6.1 81.3 5.4 3.7 1.1 2.4 3 5.9 80.3 6.2 4.1 0.9 2.6 4 6.3 82.4 4.7 3.2 1.3 2.1

The material for pulping had a relatively high proportion of ripe cherries and low proportion of unripe cherries (5.6 to 6.3%), proportion of ripe and dried cherries was average, foreign matter accounted for 0.9 to 1.3%.

Results and discussion Performance results of coffee processing machines Table 2. Performance results of Robusta processing machines

Equipment Cost USD

Capacity cherry kg/hr

Water used (m3/MT cherry)

Electricity kw/MT

Number of workers

Man-day/MT fresh cherry

Pinhalense ECO-OSVX 7158 567 3.88 10.6 3 0.66

LXT-1500 4300 1340 4.1 7.1 4 0.37 Penagos Robusta 600 7000 536 1.42 13.6 2 0.47

VINACAFE* 650 512 2.8 5.5 2 0.48 Prototype LTC Le Trung Chau 500 1150 8.7 6.52 2 0.22

Prototype Thong Nhat 150 1563 1.1 1.28 1 0.08

* Data from Thailand trials used for Robusta comparison.

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Data in Table 2 shows that the prototype LTC consumed the highest amount of water, the next is LXT-1500 and then the Pinhalense and the VINACAFE machine. The Pinhalense required the highest labour for one MT of cherry (0.66 man-day/MT), the Robusta 600 and LXT-1500 machines required 0.47 man-day/MT of cherry and 0.37 man-day/MT respectively.

Direct costs to process one kilo of green bean Table 3. Direct cost for processing cherry to parchment

Costs (VND / kg of green bean equivalent)

Machine Water Electricity Labour

Capital cost/ depreciation

** Maintenance

***

Total unit cost ****

VND/kg green bean equivalent

Pinhalense 41.9 61.2 96.6 152.1 1.5 381.3 LXT-1500 57.1 59.2 27.6 26 0.8 170.7 Robusta 600 46.2 118.9 97.6 100.1 2.1 364.9 VINACAFE* 37.0 48.1 27.6 23 1.0 136.7

*Thai data used. ** Depreciation is calculated as machine cost averaged over 15 years, two month/year, 8 working hours/day. *** Maintenance for pulper demucilagers: 6 man-day/pulper/year. **** Unit cost is the cost output from each machine (wet cleaned parchment converted to a clean dry (12%) green bean equivalent. Unit costs of processing fresh cherry are converted to dry green bean equivalents at the ratio of 6.5 kg of fresh cherry to produce 1 kg of dry green bean at 12% moisture. Note: Costs for prototype TN masher and LTC not calculated. Costs given as green bean 12% M.C. equivalents. The VINACAFE pulper/demucilager had lowest total unit cost/kg green bean equivalent.

Pulping and mucilage removal performance Table 4 shows that pulping efficiency of the three larger commercial machines was above 95%, as they primarily used green cherry sorting technologies. The prototype Le Trung Chau machined used mashing technology and had good pulping efficiency at 96.1%. The prototype Thong Nhat used normal pulping and had low efficiency at 88.8%. The VINACAFE had slightly lower pulping efficiency as it used a simple double pulper with no green cherry sorting.

Table 4. Robusta pulping and mucilage removal performance

Products of equipment Criteria Robusta

600 Pinhalense LXT-1500

Prototype TN

Prototype LTC

VINA CAFE

Percent whole cherries passing through pulper without being pulped. 3.1 4.3 2.6 11.2 3.9 6.5

Percent pulping efficiency. 96.9 95.7 97.4 88.8 96.1 93.5 Percent (by weight) lost beans (discharged along with pulp). 0.14 0.11 0.09 0.32 0.12 0.49

Percent (by weight) skin delivered with pulped parchment after pulping. 5 3 2 11 4 6.2

Percent (by weight) parch-ment nipped or parchment skin removed in demucilager output.

6.5 4.2 3.7 7.8 7.2 4.6

Percent (by weight) reduction of parchment weight due to mucilage removal. (Weight of 1000 parchment before and after mucilage removal) (Note: 100% mucilage removal was estimated to be 18%).

14.1 15.2 9.2 - 8.6 13.4

Percent mucilage removal efficiency 78.3 84 51.4 - - 73.3 Percent (by weight) parchment coffee 11.5 8.9 42.5 - 47.8 17.3

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Products of equipment Criteria Robusta

600 Pinhalense LXT-1500

Prototype TN

Prototype LTC

VINA CAFE

with some mucilage intact (visual – 1000 beans).

Mucilage removal of the Pinhalense, Penagos and VINACAFE machines were high at 15.2%, 14.1% and 13.45 respectively. (100% removal was considered to be 18% weight reduction) The LXT-1500 was low at 9.2 % mucilage-removal. Mucilage removal efficiency for each machine was calculated at 84% for the Pinhalense, 78.3% for the Penagos, 73.3% for the VINACAFE and 51.1% for the LXT-1500.

Physical quality of coffee produced Bean quality of wet processed products are better than dry processed ones. Wet processed products with mucilage removed are better than those without mucilage fully removed. The proportion of machine-damaged beans in LXT-1500 is the lowest, which is probably due to the rubber breastplate. Table 5 shows the results to physical quality analysis for each machine.

Table 5. Bean analysis for Robusta processing equipment

Quality criteria (%)

Machines Bean colour Unripe % Insect- infested

beans % Machine-

damaged beans %

Bad beans %

Pinhalense Typical grey colour of Robusta 0.44 0.34 1.26 1.26

LXT-1500 Grey and brownish 0.27 0.4 0.67 1.43

Robusta 600 Typical grey colour of Robusta 0.35 0.29 1.45 1.36

Prototype LTC Grey and brownish 0.47 0.68 2.19 2.13

Prototype TN Grey and brownish 0.91 0.73 2.4 1.87

VINACAFE Grey and brownish 0.99 0.77 2.13 1.93 Control sample (dry processed)

Grey / brown and straw-coloured 1.1 1.42 0 3.02

Beverage/liquor quality of products Products processed by Pinhalense and Prototype LTC are assessed to have good flavour. Other products are assessed as fairly good. All produced a better, cleaner cup than natural processing. The control sample product (dry processed) is considered of average quality with a pulp and unripe flavour (Table 6).

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Table 6. Cup analysis of Robusta coffee

Processed by Aroma Flavour General evaluation

Pinhalense Fragrant, clean Typical Robusta Good LXT-1500 Fragrant, clean Strong, a little over fermented Fairly good

Penagos Fragrant mixed with impure aroma

Typical Robusta, more tart than others Moderately good

Prototype LTC Fragrant, clean Strong, clean, delicious acidy Good

Prototype TN Fragrant, clean Strong, a bit tart, a bit too fermented Moderately good

VINACAFE Fragrant, clean Typical Robusta, a bit tart, a bit over-fermented Moderately good

Control sample (dry processed) Fragrant with pulpy aroma Strong, rather high acidy, mixed

with pulp flavour Average

Conclusions and recommendations Conclusions • All pulp and mucilage-removal machines tested have a capacity appropriate for household /

farm use. All machines only need small a space are relatively easily installed and operated and do not require much operation labour.

• Three complete Robusta Pulping/Demucilaging systems (Pinhalense, Robusta 600 and LXT-1500) were tested along with three prototype machines. It is difficult to compare the commercial coffee process machines with the prototype machines.

• Pulping efficiency of the 3 larger commercial machines was all above 95%, primarily as they used green cherry sorting technologies.

• Mucilage removal of the Pinhalense, Penagos and VINACAFE machines were high at 15.2%, 14.1% and 13.45 respectively (18% of fresh cherry weight was mucilage) The LXT-1500 was low at 9.2 % mucilage-removal. Mucilage removal efficiency for each machine was calculated as: 84% for the Pinhalense, 78.3% for the Penagos, 73.3% for the VINACAFE and 51.1% for the LXT-1500.

• Water consumption of LXT-1500 was highest at 4.1m3/MT of cherry and the Robusta 600 was lowest at 1.42m3/MT of cherry.

• Bean damage was similar for all machines with LTX 1500 the lowest at 0.67% and highest in Robusta 600 at 1.45%.

• Physical and cup quality results were similar for all commercial machines with the Pinhalense machine giving the best quality cup results.

• The overall cost of the VINACAFE machine is lowest at 136.7 VND/kg, the LXT-1500 system is next at 170.7 VND/kg compared to 381.3 VND/kg and 364.9 VND/kg of bean for the Pinhalense and Robusta 600 machines respectively.

Recommendations Robusta coffee machines • The VINACAFE machine is the simplest commercial machine and is has the lowest cost /

kg processing cost. The VINACAFE has acceptable performance in terms of pulping efficiency and mucilage removal. This machine is recommended as the most appropriate for farm use but further trials in practical on-farm situations is required.

• The Pinhalense and Robusta 600 machines can also be used for wet processing cherry coffee material as performance was good but the cost /kg processing cost was high and the machinery is more complex to operate. • A green cherry separator should be designed and added to Robusta 600 machine.

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• A siphon tank and loading bucket elevator should be designed and added to Pinhalense machine.

• The LXT-1500 machine had poor mucilage removal for Robusta coffee and is not recommended in its current form.

• The Prototype Thong Nhat machine needs the masher and pulper drum should be redesigned to ensure more synchronous processing.

• The Prototype Le Trung Chau machine needs the water supply to be redesigned and improved to reduce water use as it is inefficient and excessive.

Names and addresses of machinery suppliers PENAGOS COMPANY HNOS & CIA LTDA Calle 28, No. 20 – 80 Bucaramanga Columbia

Ph: 57 7 630 1600/63 2794 Fax: 57 7 6302795/6469321

THONG NHAT MECHANICAL COMPANY 49 Nguyen Tat Thanh Buon Me Thout, Daklak Province Viet Nam

Tel: 050 952290 – 95 1960 Email: martnc@vol.vnn.vn

VINACAFE ENGINEERING ENTERPRISE 05 Truong Son Street Binh Tan Industrial Zone Nha Trang City, Khanh Hoa Province Viet Nam

Tel: 058 883193 Fax: 058 883151 Email: ckvinacafe@dng.vnn.vn

LE TRUNG CHAU 114/9 Hung Vuong Boun Me Thout, Daklak Province Daklak Viet Nam

Tel: 050 852503

PINHALENSE S/A MAQUINAS AGRICOLAS Rua Honorio Soares 80 Esp. Tso. Pinhal-SP Brazil CEP 13.990-000

Tel: 55-19 3651 1079 Fax: 55-19 3651 3602 Email: peamarketing@peamarketing.com.br

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STORAGE IMPACT ON ROBUSTA COFFEE QUALITY IN BOUN ME THOUT: RESEARCH RESULTS 2004/05 (PART I)

4*Nguyen Van Thuong, Ho Thi Phuoc ** Keith Chapman

*** Anthony Marsh

Summary An eleven-month coffee storage trial was conducted at Boun Me Thout, Viet Nam where nine types of Robusta coffee were stored in a ventilated store on pallets and in an unventilated store directly on the concrete floor. This paper reports on quality aspects of the stored coffee Part I, Part II, the following paper details fungal aspects of the same storage trial.

Monthly average temperature and air humidity in both the sealed store and the natural ventilation store were similar. However, moisture content of coffees in the sealed store was always higher than in the ventilated store. The main reason for this is that the coffee in direct contact with the cement absorbed moisture from the floor and not from the air.

Quality of coffee beans held in polypropylene bags in the ventilated store was found to be better than coffee on the concrete floor in the sealed store. In the sealed store, coffee was seriously degraded after 6 months of storage. After 11 months of storage in the sealed store the moisture content of coffee and mould increased and the coffee was of unacceptable quality. Coffee in the ventilated store was still acceptable after 11 months of storage.

It was also found that quality did not degrade as quickly if coffee was stored as dried cherry and parchment coffee rather than green bean coffee.

Unventilated coffee store

Ventilated coffee store

Introduction Temperature and relative humidity of air in a coffee store are considered key factors that impact on quality of stored coffee. Degradation of quality of coffee during storage may be accompanied by mould development and Ochratoxin A (OTA) contamination in coffee. However, there has been little research carried out in Viet Nam to find the relationship between

4 * Post-Harvest Technology Department, Western Highlands Agro-forestry Scientific Technology Institute, (WASI) Boun Me Thout, Viet Nam ** Industrial Crops Officer FAO, Thailand *** International Coffee Consultant

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relative humidity and temperature and the process of coffee quality degradation in storage. Since 2004, with the sponsorship of Food and Agriculture Organization of the United Nations (FAO-UN) the Western Highland Agro-Forestry and Science Technical Institute (WASI) conducted an experiment on coffee storage in two types of stores (in bags in a ventilated store and on a concrete floor in a poorly ventilated store) with different coffee materials (dry parchment, dried mashed coffee, dried green bean and dry cherry). The trial evaluated actual damage to coffee quality and identified types of stores and coffee materials for storage appropriate at farm level.

Objectives To compare the impact of two storage methods on coffee bean quality and to compare the impact of storage on coffee bean quality produced by different processing methods. An analysis of the risks of developing mould, OTA contamination and degraded quality of coffee stored in two different types of storage was also undertaken.

Materials and methods Materials Nine lots of coffee material (4 types of green coffee bean, 2 types of mashed coffee, 2 types of parchment coffee and 1 type of dried cherry) were used for the storage experiment. These nine lots were processed as follows:

1. Green coffee beans from mashed coffee (from a plate masher). 2. Green coffee beans from mashed coffee (from a rotor and slotted cage masher). 3. Green coffee beans from parchment coffee. 4. Green coffee beans from dry cherry. 5. Mashed and dried coffee (from a plate masher as in lot 1 above). 6. Mashed and dried coffee (from a rotor and slotted cage masher as in lot 2 above ). 7. Parchment coffee (dried by solar dryer). 8. Parchment coffee (dried by Brazilian Pinhalense Mechanical dryer). 9. Dry cherry, (whole).

Freshly mashed coffee

Plate masher, VINECAFE

Rotor and slotted cage masher, Le Trung Chau

Methodology Nine lots of coffee presenting normal quantities and qualities of smallholder Robusta coffee were stored in two warehouses at WASI (9 types of process, stored 2 ways.) Moisture content, mould growth and quality was monitored over a period of 12 months from 25 February 2004 to 25 February 2005.

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Coffee used in the storage trial was sourced from 2003/2004 solar drier trials and 2003/2004 mechanical drier trials to ensure a common history. Two storage systems were used for each set of nine coffee lots.

• Storage system 1 was in new poly sacks, stacked on pallets in a well-ventilated warehouse. • Storage system 2 was in piled heaps on the bare concrete in a poorly ventilated warehouse. Moisture samples were taken from each lot monthly. Water activity (Aw) was measured in-situ at the time of collection of moisture samples. Mycological analyses were conducted every 3 months. Temperature and relative humidity were continuously measured in the warehouses. At the end of the trial samples were cup quality tested by Cafécontrol.

Ventilated warehouse

Non-ventilated warehouse

Conditions of storage Each of the nine lots of coffee was stored in two ways:

Storage system 1: Coffee stored in woven polypropylene bags placed on a wooden pallets in a naturally ventilated warehouse (vented store). The dry (12% M.C.) weight of each of the nine lots of coffee was as follows:

I. Green coffee beans from mashed coffee: 3 bags x 50kg/bag = 150kg. II. Green coffee beans from mashed coffee: (3 bags x 50kg/bag) + 21kg = 171kg.

III. Green coffee beans from parchment coffee: 10 bags x 50kg/bag = 500kg. IV. Green coffee beans from dry cherries: (4 bags x 50kg/bag) + 17.5kg = 217kg. V. Mashed coffee (Plate masher): 5 bags x 30kg/bag = 150kg.

VI. Mashed coffee (Slotted screen masher): 5 bags x 30kg/bag = 150kg. VII. Parchment coffee: 10 bag x 40kg/bag = 400kg.

VIII. Parchment coffee: 10 bags x 40kg/bag = 400kg. IX. Dried cherries: (9 bags x 40kg/bag) + 14kg = 374kg.

Storage system 2: Coffee stored in heaps on a cement floor in a poorly-ventilated (sealed) warehouse. The weight of each of the nine lots of coffee was:

I. Green coffee beans from mashed coffee: 150 kg. II. Green coffee beans from mashed coffee: 150kg.

III. Green coffee beans from parchment coffee: 500kg. IV. Coffee beans from dried cherries: 250kg V. Mashed coffee (Plate masher): 150kg

VI. Mashed coffee (Slotted screen masher): 150kg VII. Parchment coffee: 400kg

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VIII. Parchment coffee: 300kg IX. Dried cherries: 400kg.

Coffee in a well ventilated store

Coffee in a poorly ventilated store

Mashed coffee. Vietnamese farmers have developed a number of machines which break the skin of the ripe cherry coffee to aid and speed drying of the coffee mass. This practice is called “mashing” (also called “splitting” in other countries). Mashed coffee from two types of machine was tested. Lot I coffee was prepared by a Plate masher from the VINACAFE company. Lot II coffee was prepared by a Rotor and Slotted cage masher from the Le Trung Chau company. Both machines were made in Viet Nam.

Data collected Moisture content was measured once a month from the 9 different lots and samples were taken from different layers in the lots. The coffee samples were milled/husked to obtain green bean.

• Green bean moisture measurements were taken with a Kett PM 600 moisture meter (a standard instrument when buying coffee in Viet Nam).

• Water activity (Aw) was measured monthly in-situ in each lot using an Aw meter. • Changes of air temperature and air humidity in the stores were measured by micro data

loggers which were programmed to collect hourly data for the whole period of storage. • Green coffee defect levels were evaluated monthly (Counts of 1 kg samples were made to

determine white, spongy, fermented, brown and mould beans). • Coffee cup quality was evaluated every 3 months by blind cupping using 100 g of the 1 kg

samples taken for mould assessment. • After 9 months of storage, the coffee samples were tested for Ochratoxin A (OTA) using the

VICAM flurometric method.

Results and discussion Moisture content of coffee beans Initial moisture of green bean coffee for all nine lots prior to storage was 12%. Over the nine months of storage, moisture content of beans in all beans gradually increased. After one month, moisture of the coffees piled on the cement floor in the sealed store was higher than those in the vented store in comparison with the initial moisture levels. The moisture of coffee beans in the

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sealed store increased from 1.6 to 2.9% while the coffee moisture in polypropylene bags on the wooden pallet increased only 1.1 to 1.7%. After 6 months in store, moisture of coffees in the sealed store increased greatly by 6.0 to 7.8% while the vented store coffee increased 2.8 to 4.7%.

Table 1. Moisture percentage of coffee throughout the 11 month storage trial

After 1 month After 3 months After 6 months After 9 months After 11 months Types of materials Sealed Vented Sealed Vented Sealed Vented Sealed Vented Sealed Vented

I 14.1 13.2 16.2 13.9 19.3 15.1 20.3 16.0 20.5 14.8 II 14.9 13.5 15.8 13.9 17.1 14.8 18.8 16.0 21.7 14.6 III 14.2 13.6 15.5 14.5 17.6 15.9 17.5 16.1 19.2 14.0 IV 14.2 13.6 15.0 14.1 18.8 15.9 18.5 16.2 21.6 14.3 V 13.7 13.7 15.7 14.6 19.1 16.4 18.7 16.8 21.3 14.3 VI 13.9 13.1 15.3 14.2 18.0 16.0 19.1 16.3 20.4 13.4 VII 13.9 13.7 15.9 14.7 19.8 16.5 20.8 16.4 21.8 14.2 VIII 14.0 13.6 15.9 14.6 18.3 16.0 18.9 16.0 19.6 14.0 IX 13.6 13.5 15.5 14.5 18.2 15.5 18.7 16.0 20.3 14.4

After 11 months of storage, moisture content of coffee beans in the sealed store had increased slowly and moisture of coffee in the vented store decreased from the nine-month high value. This occurred in the dry season (January 2005), where the air humidity was lower, which resulted in coffee beans losing moisture in the naturally ventilated store. Generally throughout the trial, moisture in all coffees in the sealed store was higher than those in the vented store.

The same coffee material reacted differently in each of the two stores. It was noted that in the sealed store, the coffee directly piled on the cement floor absorbed moisture from the ground surface. Consequently the moisture of coffee beans in the sealed store increased more rapidly than that in the natural ventilated store where coffee was stacked on pallets and not in contact with the floor. There were clear differences in the moisture of the nine lots of coffee in the same store.

Changes in moisture of coffee beans from parchment coffee before storage in the two stores are illustrated in Graph 1.

Table 1 clearly shows the changes in coffee bean moisture content by month in the two stores. Moisture of beans gradually increased during the rainy season from May to October 2004 in both types of stores, and it seemed to increase more slowly from November to December 2004. However, moisture of coffees in the sealed store continued to increase up to February 2005. Moisture of coffee beans of different lots in the sealed store increased over 20% (Graph 2), while moisture content of coffee in the vented store decreased, ranging from 13.4 to 14.8% (Graph 3). When comparing the Graph 2 and Graph 3, it can be seen that there were small differences in moisture content between parchment coffee, green coffee, mashed coffee and coffee cherries in each type of store.

Air temperature and relative humidity in the stores At any given temperature, coffee beans may absorb moisture from the air or lose moisture into the air because there is a difference between water potential in the beans and air water potential. The relative humidity (RH) at which a heap of coffee beans will not absorb moisture or lose moisture indicates a state here a balance between loss and absorption of water from the mass of beans has been reached. This state is called Equilibrium Relative Humidity (ERH). At air RH above 65%, coffee beans will absorb water from the air. At air RH below 65% coffee beans will slowly lose water to the air.

Graphs 4, 5, and 6 illustrate conditions of air temperature and humidity in the sealed and vented stores. Generally, temperature and the humidity in the sealed store were always higher than those in the vented store. Comparing the changes in the air temperature and humidity in the two

37

stores (refer to Table 19 and Table 20), it can be seen that temperature in the sealed store in the sunny and hot months such as April, May, December 2004 and January 2005 was only ≥ 0.5°C higher than that in the vented store. In the wet season, the difference of temperature in the two stores was small. However, in the dry months in the sealed store, air humidity was about 5% lower than that in the vented store. In the rainy season, the difference in humidity in the two stores was small. Hence, air humidity in the sealed store was not the key factor that increased moisture in coffee beans. Coffee beans in heaps on the cement floor rapidly absorbed moisture from the floor resulting in a large increase of bean moisture content after 11 months of storage and serious degradation of coffee.

In summary, except for April 2004 and part of May 2004, the conditions in the stores at Boun Me Thout are all above an RH of 65%. Thus coffee can absorb water from the air. These conditions are not good for storing coffee.

Table 2. Difference in mean monthly air temperature (°C) in the two stores

Month/ year

4/04 5/04 6/04 7/04 8/04 9/04 10/04 11/04 12/04 1/05

Sealed store

29.16 27.44 25.71 25.61 24.85 25.38 23.94 23.38 21.43 21.84

Vented store

28.50 26.85 25.43 25.29 24.43 25.13 23.63 23.16 20.65 21.40

Difference (oC)

0.66 0.59 0.28 0.32 0.42 0.25 0.31 0.22 0.78 0.44

Table 3. Difference in mean monthly relative humidity (RH%) in the two stores

Month 4/04 5/04 6/04 7/04 8/04 9/04 10/04 11/04 12/04 1/05 Sealed store

59.11 67.31 76.35 78.17 83.72 80.14 77.50 81.31 76.94 71.63

Vented store

66.3 72.29 78.52 79.90 85.43 80.76 78.41 82.15 81.37 74.85

Difference (%)

-7.19 -4.98 -2.17 -1.73 -1.71 -0.62 -0.91 -0.84 -0.43 -3.32

Quality of green bean coffee Nearly all lots of the coffee in the sealed store developed white or mouldy beans. These contaminated beans were not present after 1 month of storage, but after 3 months some white and mouldy beans were present. After 6 months of storage, almost all lots of coffee in the sealed store had white and mouldy coffee. Beans from mashed coffee were found to have the highest percentage of mould. Coffee with pulp/husk remaining such as sun-dried parchment coffee, parchment coffee dried by dryer and cherries had higher percentage of mould than mashed coffee. After 11 months of storage in the sealed store, most white beans turned into mouldy ones, leading to an increase in percentage of mouldy beans that ranged between 28% to 84.3%, with the highest percentage found in coffee beans from mashed coffee at 74-84%.

In the vented store, coffee in woven polypropylene bags placed on wooden pallets had very low percentages of white and mouldy beans. See Tables 4 and 5. After 11 months in the vented store, there was an increased percentage of white beans in different lots (Lots I, II, III and IV) with 8.3%; 24.7%; 29.1%; 11.1% respectively. For the other lots of coffee with parchment or cherries (Samples V, VI, VII, VIII and IX), after 11 months of storage, the percentage of white beans was lowest at 1.1% in coffee cherries, 0.3 to 5.5% in parchment coffee and mashed coffee.

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Table 4. Percentage of white beans occurring during storage (% w/w 300g

After 3 months After 6 months After 11 months Material Sealed

warehouse Vented

warehouse Sealed

warehouse Vented

warehouse Sealed

warehouse Vented

warehouse I 3.7 0.7 30.3 8.1 11.1 8.3 II 4.8 0.8 31.7 9.3 23.5 24.7 III 6.3 0.0 35.4 15.0 53.7 29.1 IV 0.0 0.0 0.0 2.0 29.6 11.1 V 0.0 0.0 0.0 0.0 0.0 5.5 VI 0.0 0.0 0.0 2.3 0.0 0.3 VII 0.0 0.0 0.6 1.9 0.0 1.3 VIII 0.2 0.0 0.0 1.7 0.0 5.4 IX 0.0 0.0 0.0 0.0 0.0 1.1

Note: Quality analysis by ISO 0470

Coffee stored in heaps directly on the warehouse floor seriously degraded the coffee quality. Storage of coffee cherry in polypropylene bags placed on pallets demonstrated a good option to maintain coffee quality. Coffee with cherry skin or parchment keeps quality longer than green bean coffee.

Table 5. Percentage of mouldy beans occurring during storage (% w/w 300g)

After 3 months After 6 months After 11 months Material Sealed

warehouse Vented

warehouse Sealed

warehouse Vented

warehouse Sealed

warehouse Vented

warehouse I 0.5 0.0 69.7 0.0 73.9 0.0 II 1.3 0.0 8.4 1.0 84.3 0.0 III 0.0 0.0 13.7 0.0 33.1 0.0 IV 0.1 0.0 36.7 0.0 56.0 0.0 V 0.0 0.0 8.4 0.0 76.1 0.0 VI 0.8 0.0 6.0 1.5 28.1 1.9 VII 0.0 0.0 21.5 0.0 51.2 0.0 VIII 0.2 0.0 31.7 0.0 54.3 0.0 IX 0.0 0.0 8.9 0.0 37.1 0.8

Note: Quality analysis by ISO 0470 Mould contamination of coffee is a consequence of poor storage conditions. Betacourt and Frank (1983) found that bean moisture content of 14% and 75% RH is the threshold to restrict mould development. According to results of research by Lopez Garay et al (1987), mould species Aspergillus ochraceus and Penicillium spp. affect bean colour and brewed coffee quality.

Relationship between moisture content, water activity and rate of mould development in coffee beans Apart from bean moisture content (M.C.), water activity (Aw) can be used to identify the threshold that bean quality begins to degrade. Moisture allows the development of micro-organisms, spore germination and many bio-chemical reactions. Water available for these activities depends on activity of water (Aw). Water Activity is the inverse of Equilibrium Relative Humidity (ERH) and can be expressed as a decimal (instead of % in ERH) and is measured at the surface of bean/cherry/parchment coffee which is in equilibrium with the air. Table 6 presents minimum Aw values for microorganisms to develop and spores to germinate, Bacon, C.W. et al, (1973). This table suggests that when Aw is at or above 0.85 it maybe necessary to carry out OTA analysis as moulds that generate OTA can germinate and develop at this level.

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Table 6. Minimum Aw for microorganisms to develop or spores to germinate

Microorganism Activity of water (Aw) Micro organism that creates dirty mucilage 0.98 Pseudomonas, Bacillus cereus spore 0.97 B. subtilis, C.botulinum spore 0.95 C.botulinum, Salmonella 0.93 Bacteria (majority) 0.91 Ferment (majority) 0.88 Aspergillus niger 0.85 Mould (majority) 0.80 Halophilic germ 0.75 Xerophilic mould 0.65

Table 7 shows that at coffee moisture of 15 to 16% and Aw varying between 0.73 and 0.80 are sufficient conditions for mould to develop. In a sealed warehouse, bean moisture was low with Aw less than 0.70 after 1 month of storage, so mould had not yet appeared. After 11 months of storage the bean moisture increased above 20% and in most of types of stored materials and with Aw values above 0.80, coffee was seriously degraded and had high proportion of mouldy beans.

In the vented warehouse, although mouldy beans were found in mashed coffee (1.9%) and in coffee cherry (0.8%) they were generated during the drying process rather than the storage process.

Table 8 shows the relation between M.C. and Aw in different layers of materials after 11 months of storage in sealed warehouse. Figures show that M.C. and Aw increase gradually from the top to the bottom of a heap. Once again it is confirmed that bean moisture the in sealed warehouse increased rapidly due to direct water absorption from the cement floor and not because of coffee absorbing moisture from the air.

The analysis of Graph 7 shows the correlation between M.C. and Aw is linear(R=0.88). It is obvious that bean moisture tightly relates to mould generation in coffee. It is therefore necessary to manage and control coffee moisture content at an appropriate level to minimize mould and the risk of OTA generation in coffee.

OTA is generated by two species of Aspergillus and Penicilium moulds. Plant Protection Division, WASI has identified mould species (using methods of J M.Frank – “Handbook of Mycological Methods, Project TCP/VIE/2903, 2004”) existing in stored coffee samples Vis:

• Black Aspergilli group: Aspergillus niger, A. carbonarius • Ochre Aspergilli group: A. ochraceus • Flavi Aspergilli group: A. flavi • And some other mould species

Table 9 shows that only approximately 9% of the post-harvest coffee beans were contaminated by Aspergillus niger. However, after storage most of types of coffee have a high rate of mould-contaminated beans. The mashed coffee had a high rate of A. niger contamination irrespective of storage in bean or parchment coffee and especially in coffee mashed with rotor and cage masher from the Le Trung Chau company.

Table 10 shows that coffee beans are not contaminated by A. carbonarius after harvest. However, after a period of storage, most of types of coffee are contaminated by A. carbonarius.

Table 11 shows that all types of coffee, after being stored in a sealed warehouse are contaminated by A. ochraceus. The proportion of A. ochraceus contaminated beans gradually increased during storage in the sealed warehouse. After 3 months only 1.2% of beans were

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infected by A. ochraceus mould, after 9 months this figure rose to 22%. However in the vented store only 0.4% of beans were infected by A. ochraceus, after 9 months.

Table 7. Relation between bean Moisture Content (M.C.), Water Activity (Aw) and proportion of Mouldy Beans in sealed store

After 1 month After 3 months After 6 months After 11 months Material lot m.c.

% Aw Mouldy

bean % m.c. %

Aw Mouldy bean %

m.c. %

Aw Mouldy bean %

m.c. %

Aw Mouldy bean %

I 14.1 0.700 0.0 16.2 0.750 0.5 19.3 0.823 69.7 20.5 0.918 73.9 II 14.9 0.653 0.0 15.8 0.737 1.3 17.1 0.758 8.4 21.7 0.892 84.3 III 14.2 0.688 0.0 15.5 0.706 0.0 17.2 0.779 13.7 19.2 0.855 33.1 IV 14.2 0.602 0.0 15.0 0.779 0.1 18.8 0.825 36.7 21.6 0.902 56.0 V 13.7 0.678 0.0 15.7 0.789 0.0 19.1 0.856 8.4 21.3 0.881 76.1 VI 13.9 0.617 0.0 15.3 0.735 0.8 18.0 0.806 1.0 20.4 0.904 28.1 VII 13.5 0.625 0.0 15.9 0.766 0.0 20.6 0.799 21.5 21.8 0.881 51.2 VIII 14.0 0.660 0.0 15.9 0.763 0.2 18.5 0.864 31.7 19.6 0.878 54.3 IX 13.6 0.664 0.0 15.5 0.743 0.0 18.1 0.807 8.9 20.3 0.886 37.1

Table 8. Relation between bean Moisture Content (M.C.), Water Activity (Aw) and proportion of Mouldy Beans in vented store

After 1 month After 3 months After 6 months After 11 months Material lot m.c.

% Aw Mouldy

bean % m.c. %

Aw Mouldy bean %

m.c. %

Aw Mouldy bean %

m.c. %

Aw Mouldy bean %

I 13.2 0.561 0.0 13.9 0.643 0.0 15.1 0.680 0.0 14.8 0.755 0.0 II 13.5 0.576 0.0 13.9 0.644 0.0 14.8 0.688 1.0 14.6 0.744 0.0 III 13.6 0.591 0.0 14.5 0.652 0.0 15.9 0.680 0.0 14.0 0.740 0.0 IV 13.6 0.574 0.0 14.1 0.623 0.0 15.9 0.694 0.0 14.3 0.737 0.0 V 13.7 0.570 0.0 14.6 0.663 0.0 16.4 0.765 0.0 14.3 0.755 0.0 VI 13.1 0.608 0.0 14.2 0.661 0.0 16.0 0.747 1.5 13.4 0.720 1.9 VII 13.7 0.606 0.0 14.7 0.652 0.0 16.5 0.737 0.0 14.2 0.772 0.0 VIII 13.6 0.689 0.0 14.6 0.701 0.0 16.6 0.749 0.0 14.0 0.728 0.0 IX 13.5 0.593 0.0 14.5 0.681 0.0 16.1 0.728 0.0 14.4 0.767 0.8

Table 9. Relation between coffee Water Activity (Aw) and coffee Moisture Content (M.C.) after 11 months in a sealed store

Top layer (5cm) Middle layer (30cm) Lower layer (60cm) Material lot Aw m.c. (%wb) Aw m.c. (%wb) Aw m.c. (%wb)

I 0.872 17.9 0.916 20.0 0.966 25.1 II 0.848 16.5 0.892 21.4 0.973 28.0 III 0.796 15.6 0.855 17.2 0.864 27.0 IV 0.844 17.1 0.902 19.8 0.979 27.8 V 0.845 16.8 0.881 21.7 0.930 25.4 VI 0.820 14.9 0.904 21.1 0.945 24.7 VII 0.839 18.2 0.881 19.5 0.964 26.7 VIII 0.842 15.9 0.878 20.1 0.938 22.7 IX 0.874 15.8 0.886 24.9 0.939 23.6

Table 10. Percentage of coffee bean contaminated by Aspergillus niger

Material

3 months 6 months 9 months

41

lot Sealed store Vented store Sealed store Vented store Sealed store Vented store I 98 102 44 71 20 87 II 121 124 100 78 60 119 III 51 60 32 25 26 30 IV 45 42 40 28 17 34 V 83 63 80 48 54 119 VI 71 45 97 18 46 126 VII 45 44 59 41 9 47 VIII 10 11 13 5 0 13 IX 17 12 24 6 20 9

Table 11. Percentage of coffee bean contaminated by Aspergillus carbonarius

After 3 months After 6 months After 9 months Material lot

Sealed store Vented store Sealed store Vented store Sealed store Vented store I 42 13 9 57 3 62 II 0 16 11 26 0 24 III 10 5 11 5 0 0 IV 56 34 13 70 3 20 V 0 16 9 60 16 0 VI 18 36 0 73 0 0 VII 6 0 7 4 0 0 VIII 5 3 3 1 0 3 IX 3 6 0 12 0 6

Table 12. Percentage of coffee bean contaminated by Aspergillus ochraceus

After 3 months After 6 months After 9 months Material lot Sealed store Vented store Sealed store Vented store Sealed store Vented store

I 0 0 40 0 63 0 II 6 0 7 0 30 0 III 1 0 11 0 23 0 IV 0 0 24 0 39 0 V 0 0 0 0 3 1 VI 0 0 1 0 1 3 VII 1 0 14 0 16 0 VIII 3 0 43 0 21 0 IX 0 0 4 0 4 0

Table 13. Cup taste of coffee after 6 months of storage in a naturally ventilated store

Lot Aroma Flavour Evaluation I Soft fragrant, average aroma, clean Typical Robusta, a bit tasteless and not special Average II Soft fragrant, clean Relatively balanced flavour, no mouldy flavour Fair III Soft fragrant, a normal cup of coffee Average flavour, thin body Average IV Fragrant, fair aroma concentration Average flavour, 1 cup slightly mouldy flavour Average V Average fragrant, one cup had some

rotting pulp odour Average flavour and varied among cups: 1 cup had a mixed flavour

Average

VI Average, fragrant, a normal cup Average flavour, thin body Average VII Fragrant, but not clean Relatively balanced flavour but 1 cup had

fermented flavour Average

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VIII Fragrant, clean, delicious Balanced flavour, a bit acidy Good IX Fragrant mixed with phenolic odour All cups have distinct chemical and fruity taste Poor

Table 14. Cup taste of coffee after 6 months of storage in a sealed store

Lot

Aroma Flavour Evaluation

I Tasteless and a little dirty odour Average flavour Poor- Average II Terrible oily odour Acceptable flavour but less delicious Poor III Fragrant and clean, low aroma

concentration Balanced flavour but thin body, woody flavour Average

IV Fragrant mixed with hard sour odour Moderate body, harsh and slightly dirty Poor- Average V Fragrant and average aroma

concentration Fair body but one cup had pulp-fermented flavour

Average

VI Fragrant and average aroma concentration

Fair body, slightly mouldy flavour Average

VII Little fragrant and distinct mouldy odour Distinct mouldy flavour Unacceptable VIII Rather fragrant but mixed with slight

mouldy odour Fair flavour with acidity and slightly mouldy flavour, unlikely to be recognized

Average

IX Terrible odour, no coffee aroma recognized

Unacceptable flavour (foul, mouldy and dirty) Unacceptable

Table 15. Cup taste of coffee after 9 months storage in a naturally ventilated store

Lot

Aroma Flavour Evaluation

I Slightly fragrant, a little smelly and old A bit acid, balanced flavour but with a tendency towards tasteless

Poor-average

II Rather fragrant but a little old Balanced flavour with a tendency towards tasteless Average III Rather fragrant but a little old Balanced flavour but thin body Average IV Rather fragrant but a little old Balanced flavour but thin body Average V Rather fragrant but a little pulp odour Balanced flavour but a cup had phenol flavour Poor VI Average, old fragrant Balanced flavour and a little acidy Average VII Rather fragrant but a little old Average flavour mixed with some fermented flavour Poor-

average VIII Rather fragrant, clean Balanced flavour and a little acid Fairly good IX Fairly fragrant but a little fermented

pulp aroma Average flavour mixed with fermented flavour Poor-

average Table 16. Cup taste of coffee after 9 months storage in sealed store

Lot Aroma Flavour Evaluation I Aroma degraded, oily, dirty, no longer coffee

aroma Distinct mouldy and dirty flavour Rejected

II Rather fragrant mixed with slight mouldy odour Balanced flavour but a bit tasteless, a little mouldy flavour

Poor – Rejected

III Rather fragrant mixed with slight mouldy odour Acceptable flavour Poor-Average IV Aroma degraded, oily, dirty, no longer coffee

odour Distinct mouldy and dirty flavour Rejected

V Aroma degraded, oily, dirty, no longer coffee aroma

Distinct mouldy and dirty flavour Rejected

VI Still coffee aroma but tasteless Distinct mouldy and dirty flavour Rejected VII No longer typical coffee aroma Tasteless, distinctly mouldy and

dirty flavour Rejected

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VIII Slight fragrant mixed with mouldy odour Distinct mouldy and dirty flavour Rejected IX Aroma degraded, oily mixed with phenol, terribly

dirty, no coffee aroma Terribly dirty odour, no name for this type of coffee

Rejected

Cup Quality of coffee The results of coffee cup quality (Tables 13 to 16) show that coffee stored in a vented store gives better quality than coffee stored in a sealed store for both 6 and 9 months.

After 6 months most of the coffee from the sealed store had a thin body and no typical coffee flavour. The coffees had mixed flavours and were sour, mouldy and had a distinct woody flavour.

After 9 months storage in the sealed store all the coffee lots were rejected while coffees in the ventilated were poor but acceptable.

OTA analysis Table 17. Analysis of Ochratoxin in coffee after 9 months storage (by VICAM method)

Coffee from sealed store Lot Form of coffee Ochratoxin A content

(µg kg – 1) Notes

I Bean from dry mashed cherry 4 A lot of mouldy beans II Bean from dry mashed cherry 2 III Bean from sun dried parchment 0 IV Bean from sun dried cherry 1 V Sun dried parchment 3 A lot of mouldy beans VI Machine dried parchment 3 A lot of mouldy beans VII Dry mashed cherry 1 ( as in I) 1 VIII Dry mashed cherry 2 ( as in II) 0 IX Sun dried cherry 0 Average 1.56

*Samples tested by standard VICAM method for Green Bean at CAFECONTROL HCM city, Wedne

sday, June 15, 2005 **N.B. J.M.Frank (pers. com.) points out that the VICAM method for OTA determination in green bean coffee often produces false positives detection of OTA compared with Thin Layer Chromatography (TLC) and HPLC detection. Thus some OTA detected by VICAM may not be real. In most cases OTA level is below international accepted levels)

Coffee from ventilated store Lot Form of coffee Ochratoxin A content

(µg kg – 1) Notes

Forms of dry storage coffee I Bean from dry mashed cherry 1 II Bean from dry mashed cherry 0 III Bean from sun dried parchment 0 IV Bean from sun dried cherry 1 V Sun dried parchment 0 VI Machine dried parchment 0 VII Dry mashed cherry (as in I) 1 VIII Dry mashed cherry (as in II) 0 IX Sun dried cherry 0 Average 0.33

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Conclusions and recommendations Conclusions 1. Monthly average temperature and air humidity in both a sealed store and a natural

ventilated store were similar. 2. Moisture content of coffees in the sealed store was always higher than in the vented store.

The main reason was that coffee was in direct contact with the cement and absorbed moisture from the floor.

3. Only small moisture differences were found between coffee cherry, parchment coffee and green bean coffee in the same type of store.

4. Quality of coffee beans held in woven polypropylene bags in the ventilated store was found to be better than coffee heaped on the concrete floor in the sealed store. In the sealed store, coffee degraded seriously after 6 months of storage. After 11 months of storage moisture content of coffee and mould increased. There was a close correlation between moisture content (M.C.) of green bean coffee and activity of water (Aw).

5. Storing different types of coffee materials in woven polypropylene bags on pallets in natural ventilation stores minimises degradation of bean quality. It is better to store dried cherry and parchment coffee than green bean coffee.

6. Coffee in the ventilated store had lower risk of mould contamination than in the sealed store but showed a tendency for greater A. carbonarrius contamination. Also coffee in sealed store demonstrates a tendency for greater A. ochraceus contamination.

7. Quality of coffee liquor is degraded by duration of coffee material in storage. Coffee stored in the naturally ventilated store and placed on wooden pallets gave acceptable quality of brewed coffee. After 9 months of storage the brewed flavour was still acceptable. Coffee stored in a sealed store and piled directly on cement floor after 9 months had a mouldy and dirty flavour, which was not acceptable.

Recommendations 1. Coffees should not be stored directly on a concrete floor in a store. 2. Coffee should b stored in a ventilated stored on a pallets. 3. Coffee should be stored as cherry or parchment rather than as green bean. 4. Coffee should not be stored in environment where RH is over 65%. 5. A new trial on storage should be carried out with the coffees kept in polypropylene bags

that are placed on wooden pallets and stored in sealed store to determine outcomes with respect to quality OTA and M.C.

6. Special polyethylene bags developed by IRRI for use to manage rice moisture could be tested for coffee storage.

References Bacon, C.W. et al. 1973. Production of Penicillic acid and Ochratoxin A on Poultry Feed by Aspergillus ochraceus: Temperature and Moisture Requirements. Appl. Microbiol 26:155 – 160.

Betancourt, L.E. and Frank, H.K. 1983. Bedingungendes Mikrobiellen Vederbs von Grunem Kaffee. Dtsch. Lebensm. Rundsch. 79:366-369.

Lopez Garay, C., et al. 1987. Use of Gamma Radiation for the Preservation of Coffee Quality during Storage. In: Proc. 12th ASIC Coll, 771-782.

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Graph 1. Variations of M.C. of green bean in two stores

Graph 2. Varietion of M.C. of coffee bean in different coffee materials in sealed store

46

0

2

4

6

8

10

12

14

16

18

4/04 5/04 6/04 7/04 8/04 9/04 10/04 11/04 12/04 2/05Month/year

MC (%wb)

Bean from Masher 1

Bean from Masher 2Bean from ParchmentBean from dried cherry

Mash from Masher 1

Mash from Masher 2

Parchment (sun-dried)Parchment (mechanical-dried)

Cherry (sun-dried)

Graph 3. Variations of M.C. of green bean in different materials in vented store

0

5

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15

20

25

30

4/04 5/04 6/04 7/04 8/04 9/04 10/04 11/04 12/04Month/year

Temp. (oC)

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40

50

60

70

80

90RH (%)

TemperatureRelative humidity

Graph 4. Air temperature and relative humidity in sealed store

47

Graph 5. Air temperature and relative humidity in sealed store

0

5

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35

4/04 5/04 6/04 7/04 8/04 9/04 10/0411/0412/04Month/year

Temperature (oC)

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40

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60

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80

90

RH (%)

Temperature in sealed storeTemperature in vented store

RH in sealed storeRH in vented stored

Graph 6. Air temperature and relative humidity in vented and sealed stores

0

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4/04 5/04 6/04 7/04 8/04 9/04 10/04 11/04 12/04Month/year

Temp. (oC)

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90RH (%)

Temperature Relative humidity

48

y = 0.0365x + 0.1685R20.8819 =

00.10.20.30.40.50.60.70.80.9

1

0 5 10 15 20 25 m.c (wb)

aw

Graph 7. Relationship between M.C. of green bean and Aw

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EFFECTS OF STORAGE CONDITIONS ON FUNGAL OCCURRENCE IN GREEN BEANS OF ROBUSTA COFFEE, STORED AS GREEN

BEAN, PARCHMENT AND CHERRY (PART II) 5*Tran Kim Loang, Ha Thi Mao et al.

**John Michael Frank

Summary Several different forms of coffee were compared. Some coffee was stored in sacks in well-ventilated storage conditions and some stored in heaps in poorly ventilated store over a storage period of one year. The Part I paper on storage reported on quality effects and OTA in storage. This paper covers fungal occurrence. The coffee in the poorly ventilated space gained moisture fairly rapidly and crossed into the OTA production zone in three to six months. In well-ventilated conditions none of the coffee forms exceeded the Aw 0.80 level but did increase in Aw and was showing signs of visible mould after one year.

Because of the high infection rates at the first sampling, it was not possible to be certain whether overall infection increased but visible mould on the coffee did increase along lines that could have been predicted by the observed changes in Aw. Increased rates of mouldy beans were recorded as the coffee moved beyond an about Aw 0.75, thus there was gross mould in the poorly-ventilated store and only a small increase in the last quarterly sampling in well-ventilated conditions.

The infection rate of coffee by A. niger complex species either increased or did not change in the dryer conditions, but actually fell in the wetter conditions of poor ventilation. This might be due to premature breaking of dormancy.

The most notable increase in infection rate was recorded by the ochre Aspergilli in the damp conditions of poor ventilation except when stored as whole cherry. It is likely that this increase was accomplished through vegetative growth, hence there is a risk that this coffee became contaminated by OTA over the final 4 to 6 months of the storage.

A. carbonarius apparently increased in the well-ventilated conditions, but this is not a plausible finding because the Aw recorded would not permit this species to grow or germinate. Because of technical difficulties in identifying this species and the pattern of change being divorced from the measured moisture availability pattern, it is likely these data are spurious.

There was evidence of Aspergillus flavi at about the detection limit (1.4%), but there was no indication that these important fungi increased under any of the storage conditions.

These results demonstrate that, storage in climatic conditions similar to Buon Me Thout in heaps in unventilated stores, is not appropriate, even for two months. It becomes a potentially serious safety issue after about six months. The design of the trial did not permit conclusions relating to the efficacy of polypropylene sacks versus heaps, since both the mode of storage and the conditions of the storeroom were different in the comparison.

Beans were generally more susceptible to increases in infection rate and whole cherry showed significant resistance to new infection by ochre Aspergilli, the most important OTA producers, in comparison to the other coffee forms tested. Cupping tests in other countries have indicated that stored whole cherries are more similar to new season crop than storage in the other forms. Apparently, the bean enclosed in the intact husk is a more stable entity than the green bean, the parchment or parchment mixed with husk, after split or mashed cherry processing.

5 *Plant Protection Department - Western Highlands Agro-Forestry Scientific and Technical Institute (WASI) ** International Consultant

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Introduction Deterioration of commodities during storage causes large global losses every year. Because the value of coffee is peculiarly dependent on its sensory quality, it can be spoiled by small changes as well as normal spoilage. Fungal activity contributes to both of these and also can produce toxins that can make a commodity unsafe or unacceptable by law.

Water is required for fungal growth, so once the water is removed during the drying procedure in processing, the control of moisture in the commodity subsequently becomes the key objective. This includes storage, handling or curing and transport. Some fungi can grow in very dry conditions but the OTA-producing fungi as well as most spoilage species found in coffee are mesophilic: they require moderate moisture conditions so are somewhat easier to control. The OTA-producing species of significance in coffee are Aspergillus ochraceus and several related species, A. carbonarius and perhaps occasionally A. niger.

Depending on species, these species require a water activity (Aw, a measure of water availability) in the commodity between 0.78 and 0.85 for growth, and between 0.80 and 0.92 for OTA production. The lower OTA production limit of 0.80 gives the key parameter for assessing the quality of the storage conditions with regard to mycotoxin contamination. In moisture content (M.C.) terms this corresponds to between 15 and 25% M.C. (wb). This broad range reflects differences in batches and forms of coffee found in the production chain.

On-farm storage is commonly practiced in Viet Nam and the survey of farms found that farmers store coffee as green coffee or cherry in woven polypropylene sacks or in heaps. The cherry may be stored as whole cherry but with more use of cherry masher technology it is increasingly stored as dried split cherry.

There are no standard conditions in farmers’ stores. In particular, the ventilation can be poor so it was this aspect that was investigated. This report discusses impact of storing Robusta coffee under conditions intended to simulate good and poor on-farm storage. Coffee in four forms from the 2003 season was stored in sacks on pallets in a well-ventilated store and in heaps in a poorly ventilated store at WASI, Buon Me Thuot.

Metholodogy Experimental set-up Nine lots of coffee material (4 types of green coffee bean, 2 types of mashed coffee, 2 types of parchment coffee and 1 type of dried cherry) were used for the storage experiment. These 9 lots of coffee were processed as follows:

1. Green coffee beans from mashed coffee (from a plate masher, VINACAFE). 2. Green coffee beans from mashed coffee (from a rotor and slotted cage masher, Le

Trung Chau). 3. Green coffee beans from parchment coffee. 4. Green coffee beans from dry cherry. 5. Mashed and dried coffee (from a plate masher as in lot 1 above, VINACAFE). 6. Mashed and dried coffee (from a rotor and slotted cage masher as in lot 2 above, Le

Trung Chau). 7. Parchment coffee (dried by solar dryer). 8. Parchment coffee (dried by Brazilian Pinhalense mechanical dryer). 9. Dry cherry (whole). A description of the processing equipment mentioned above can be found in the section “Trials on Domestic and Imported Wet Coffee Processing Equipment Report 1”.

Two lots of each of these nine processing products, produced in 2003 /2004 solar and mechanical dryer trials, were bagged in quantities and qualities typical of a smallholder

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Robusta coffee operation. One set was stored in each of two warehouses at WASI over 12 months from 25 February 2004 to 25 February 2005:

• Storage system 1 was in new woven polypropylene bags, stacked on pallets in a well-ventilated warehouse.

• Storage system 2 was coffee in piled heaps on the bare concrete in a poorly ventilated warehouse.

Storage system 1: Coffee stored in woven polypropylene bags placed on wooden pallets in a naturally ventilated warehouse (vented store). The dry (12% M.C.) weights of each of the nine lots of coffee were:

I. Green coffee beans from mashed coffee: 3 bags x 50 kg/bag = 150 kg II. Green coffee beans from mashed coffee: (3 bags x 50 kg/bag) + 21kg = 171kg

III. Green coffee beans from parchment coffee: 10 bags x 50 kg/bag = 500kg IV. Green coffee beans from dry cherries: (4 bags x 50 kg/bag) + 17.5kg = 217kg V. Mashed coffee (plate masher): 5 bags x 30 kg/bag = 150 kg

VI. Mashed coffee (slotted screen masher): 5 bags x 30 kg/bag = 150kg VII. Parchment coffee: 10 bag x 40 kg/bag = 400 kg

VIII. Parchment coffee: 10 bags x 40 kg/bag = 400 kg IX. Dried cherries: (9 bags x 40 kg/bag) + 14 kg = 374 kg

Storage system 2: Coffee stored in heaps on a cement floor in a poorly-ventilated warehouse (sealed warehouse). The weight of each of the nine lots of coffee were:

I. Green coffee beans from mashed coffee: 150 kg II. Green coffee beans from mashed coffee: 150 kg

III. Green coffee beans from parchment coffee: 500 kg IV. Coffee beans from dried cherries: 250 kg V. Mashed coffee (Plate masher): 150 kg

VI. Mashed coffee (Slotted screen masher): 150 kg VII. Parchment coffee: 400 kg

VIII. Parchment coffee: 300 kg IX. Dried cherries: 400 kg.

Coffee in ventilated store

Coffee in unventilated store

Sampling

Moisture content was measured once a month from each of the nine lots of coffee in the two warehouses. Coffee samples were taken from different layers in the lots and milled /husked to obtain green bean.

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• Green bean moisture measurements were taken with a Kett PM 600 moisture meter (a standard instrument when buying coffee in Viet Nam).

• Water activity was measured after 1,3,6 and 11 months in-situ in each lot using an Aw ‘Hygropalm’ meter.

• Changes of air temperature and air humidity in the stores were measured by Micro Data Loggers. These were programmed to collect hourly data for the whole period of storage.

• Green coffee defect levels were evaluated monthly (counts of 1 kg samples were made to determine white, spongy, fermented, brown and mouldy beans).

• Samples for mycological analysis taken every three months amalgamated from 3 areas (top, middle and bottom) in each stored coffee treatment.

• Coffee cup quality was evaluated by “blind” cupping (100 g of the 1 kg samples taken for mould assessment were cup tasted every 3 months).

• At the end of the experiment, the coffee samples were tested for Ochratoxin A (OTA) using the VICAM flurometric method.

Fungal analysis Fungi isolation and identification were carried out following Handbook of Mycological Methods: Enhancement of Coffee Quality Project TCP/VIE/2903 (A), 2004. In brief, the beans were surface-sterilized with 1% hypochlorite for 10 minutes, rinsed in sterile water, blotted on sterile filter paper and plated out seven beans per plate of the enumeration medium DG18. Incubation was for a minimum of 10 days though preliminary counts may be necessary depending on the out-growth rate and density of the fungi.

In this study, an analysis comprised 70 beans on 10 plates. Species determination cannot be reliably accomplished on DG18 media in the groups of interest, so naming conventions are adapted to accurately reflect the information: ochre Aspergilli includes all the buff-coloured species of Aspergillus and niger Aspergilli refer to all of the dark-brown to black species. Microscope observation of the conidia and conidial heads removed using the cello-tape method (preferably mounted in lactic acid with anilene blue) was used to distinguish A. carbonarius and A. japonicus from A. niger complex species.

Results and discussion Figure 1 shows the changes in Aw in the coffee sacks and heaps during the storage period in the two stores. The differences between the forms of coffee within the stores are relatively small compared to those between the stores. The two sets of samples are delimited by the polynomial curve of best fit for the wettest (solid line) and driest treatment (broken line) of each store (red = unventilated store; green = ventilated store).

Both of the driest products, as measured by Aw or moisture content are beans, and the wettest two are variously split cherry and parchment. In the unventilated store the worst performing coffee product reached the OTA production limit within three months, the others after about six months. These coffees were thus in a condition to support fungal growth and development for about six months of the experiment. Though coffee in the ventilated store apparently took up water, the Aw never reached a point where any but the most xerophilic fungi could grow.

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Figure 1. Water activity (Aw) of coffee stored in different forms in ventilated (green) and unventilated (red) stores

The ventilated store coffee forms are enclosed in green and the corresponding coffees in the unventilated store in red with the broken line representing the driest and the solid line the wettest treatment of each. Because the first total infection rate is close to 100%, it is difficult to confirm that new infection was taking place during the storage period (Table 1) particularly in the first six months, when we would expect to see a difference between the two sets of storage conditions based on the Aw data. The frequency of visually mouldy beans, however, does increase as expected in the unventilated store (Table 2).

Table 1. Total fungal infection rate of coffee seeds during the storage period

Poorly ventilated (months) Well ventilated (months) Treatment as beans

3 6 9 3 6 9 (I) Masher 1 100 100 100 99 98 100 (II) Masher 2 100 99 91 100 99 91 (III) P Solar 66 81 90 71 56 44 (IV) Sun cherry coffee 91 94 100 96 91 87 Treatment as other (V) Masher 1 87 94 100 86 84 91 (VI) Masher 2 80 89 97 87 76 84 (VII) P Solar 70 80 96 57 60 37 (VIII) P Mech 41 84 93 19 19 43 (IX) Cherry coffee 24 76 76 29 24 16 Masher 1 = plate masher; Masher 2 = slotted cage masher – these products were stored as either green bean or dried split cherry; Mech = mechanical dryer (Pinhalense design); P = parchment coffee Note that there was early indication of mould development after three months, though this may be superficial growth over the surface and may not represent infection. The figures after six months are more likely to represent infection unless in some cases the species itself is incapable of colonizing the internal tissues. The analysis method includes a rigorous surface sterilization step so would remove anything that had not penetrated the seed tissues. In the interval between three and six months, there was strong mould development in four of the coffee products,

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8 9 10 11 12

storage period (months)

Aw

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moderate development in four, and nil in the remaining one as almost all the coffees had an Aw over 0.80. Coffee stored as beans and cherries and parchment performed about equally.

Table 2. Changes in frequency of visually mouldy beans (units are % of beans)

Poorly ventilated (months) Well ventilated (months) Treatment as beans

1 3 6 11 1 6 11

(I) Masher 1 0 0.5 69.7 73.9 0 0 0 0 (II) Masher 2 0 1.3 8.4 84.3 0 0 1 0 (III) P Solar 0 0 13.7 33.1 0 0 0 0 (IV) Sun cherry coffee 0 0.1 36.7 56 0 0 0 0 Treatment as other (V) Masher 1 0 0 8.4 76.1 0 0 0 0 (VI) Masher 2 0 0.8 1 28.1 0 0 1.5 1.9 (VII) P Solar 0 0 21.5 51.2 0 0 0 0 (VIII) P Mech 0 0.2 31.7 54.3 0 0 0 0 (IX) Cherry coffee 0 0 8.9 37.1 0 0 0 0.8

Masher 1 = plate masher; Masher 2 = slotted cage masher – these products were stored as either green bean or dried split cherry; Mech = mechanical dryer (Pinhalense design); P = parchment coffee Different fungi species have different potential for spoiling commodities so it is important to be able to assess the impact of storage on individual taxa in order to assess the quality of the storage. A. niger complex include a number of taxa which are impossible for the non-specialist to distinguish, and in some cases, for which there is no consensus of specialists on their status. It should exclude A. carbonarius and the uniseriate black Aspergilli, but in practice this is problematic, especially with Robusta cherry coffee where the infection rate of black Aspergilli is extremely high. Well-tutored non-specialists can distinguish these three groups with confidence, but only if a rather tedious and time-consuming procedure is consistently applied — short-cuts invalidate the outcome.

A. niger complex infection rate fell in poorly ventilated storage conditions (Table 3) in the background of increasing frequency of mouldy beans but a probably stable rate of infection. Interestingly they seem to be stable in the dryer conditions of the well-ventilated store. This is not unknown and may be explained by the fact that in dry conditions the fungus is in a dormant state and is stable. In slowly improving conditions, the fungus may be encouraged to break dormancy pre-maturely and perish as a result.

Since the overall infection rate does not apparently fall, we may assume that more xerophilic species have become active (Eurotium sp. were noted in the analysis) or that other mesophiles are out-competing others.

In comparing the forms of coffee stored, it is difficult to draw firm conclusions because the magnitude of the differences is close to the expected error of measurement/sampling of the analysis. Possibly, the product of the cage masher stored as beans shows a smaller reduction than the other bean origins and likewise, the product of both mashers when the husk and beans are stored together may protect A. niger complex somewhat better than the other forms. The implication is that the members of this group are not growing much under the storage conditions or at least did not grow much before the hydration had reached a higher range.

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Table 3. Infection rates of A. niger complex species during storage

Poorly ventilated (months) Well ventilated (months) Treatment as beans 3 6 9 3 6 9

(I) Masher 1 98 44 20 102 71 87 (II) Masher 2 121 100 60 124 78 119 (III) P Solar 51 32 26 60 25 30 (IV) Sun cherry coffee 45 40 17 42 28 34 Treatment as other (V) Masher 1 83 80 54 63 48 119 (VI) Masher 2 71 97 46 45 18 126 (VII) P Solar 45 59 9 44 41 47 (VIII) P Mech 10 13 10 11 5 13 (IX) Cherry coffee 17 24 20 12 6 9 Masher 1 = plate masher; Masher 2 = slotted cage masher – these products were stored as either green bean or dried split cherry; Mech = mechanical dryer (Pinhalense design); P = parchment coffee A. carbonarius is the main OTA-producing species amongst the black Aspergilli. Two new species assigned to the group (A. sclerotiniger and A. lactoccoffeatus) that produce large amounts of OTA are rare. Persistence of A. carbonarius appears to be greater in beans than in the various forms of cherry tested and in parchment (Table 4). The temporary increases in the well-ventilated conditions are difficult to rationalise since this species is not capable of growth at the Aw levels measured during that period. This result could be an indication of mis-identification. Otherwise there was a general tendency for A. carbonarius to disappear during a nine-month storage period.

Table 4. Infection rates of A. carbonarius during storage (detection limit is 1.4%)

Poorly ventilated (months) Well ventilated (months) Treatment as beans

3 6 9 3 6 9

(I) Masher 1 42 9 3 13 57 62 (II) Masher 2 0 11 0 16 26 24 (III) P Solar 10 11 0 5 5 0 (IV) Sun cherry coffee 56 13 3 34 70 20 Treatment as other (V) Masher 1 0 9 16 16 60 0 (VI) Masher 2 18 0 0 36 73 0 (VII) P Solar 6 7 0 0 4 0 (VIII) P Mech 5 3 0 3 1 3 (IX) Cherry coffee 6 7 0 0 4 0

Masher 1 = plate masher; Masher 2 = slotted cage masher – these products were stored as either green bean or dried split cherry; Mech = mechanical dryer (Pinhalense design); P = parchment coffee There are some 25 species or so in this group of buff-coloured bi-seriate Aspergilli. Several commonly produce OTA but some important ones do not. Chief amongst the non-producers is A. melleus, which is very similar to A. ochraceus, and cannot be reliably distinguished from it by the non-specialist. Two new OTA-producing species have recently been described (A. steynii and A. subochraceus) and are relatively common in coffee but are indistinguishable from A. ochraceus by the non-specialist.

There was a marked increase in the ochre Aspergilli in coffee in the poorly ventilated store (Table 5). An increase in infection implies a considerable amount of growth, since in storage, a new infection is most likely produced by growth from one bean to another and subsequent

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colonisation. This implies that this coffee became contaminated with OTA during storage. Interestingly, the smallest change is in the intact cherry. Only bean from the plate masher may have experienced a greater than average increase – the other data are uniform within methodological uncertainty.

Table 5. Infection rates of ochre Aspergilli during storage (detection limit is 1.4%)

Poorly ventilated (months) Well ventilated (months) Treatment as beans

3 6 9 3 6 9

(I) Masher 1 0 40 63 0 0 3 (II) Masher 2 6 7 30 0 0 0 (III) p Solar 1 11 23 0 0 0 (IV) Sun cherry coffee 0 24 39 0 0 0 Treatment as other (V) Masher 1 1 11 23 0 0 0 (VI) Masher 2 0 24 39 0 0 0 (VII) P Solar 1 14 16 0 0 0 (VIII) P Mech 3 43 21 0 0 0 (IX) Cherry coffee 0 4 4 0 0 0 Masher 1 = plate masher; Masher 2 = slotted cage masher – these products were stored as either green bean or dried split cherry; Mech = mechanical dryer (Pinhalense design); P = parchment coffee Some members of the flavi section of the genus Aspergillus, produce aflatoxin, most notably A. flavus and A. parasiticus. A survey of coffee sampled from farms in Thailand showed some 12 of 88 samples contained aflatoxin at levels between 1 and 2 ppb.

Several other species are harmless, some, in fact, are used in food fermentation, but they are not very easily distinguished from the toxigenic species. A. oryzae, a fast growing aggressive mould, is the most common representative of the section in coffee. It can be identified fairly easily and is harmless. The numerical changes shown in Table 6 do not represent real changes, rather methodological error associated with a species occurring at about the detection limit. One could say that the flavi Aspergilli occur at about 1% in these coffees and do not apparently change through storage over the nine-month period.

Table 6. Infection rates of flavi Aspergilli during storage (detection limit is 1.4%)

Poorly ventilated (months) Well ventilated (months) Treatment as beans

3 6 9 3 6 9 (I) Masher 1 1 1 1 0 2 3 (II) Masher 2 1 1 0 1 3 0 (III) P Solar 4 1 0 1 1 0 (IV) Sun cherry coffee 0 0 0 0 4 0 Treatment as other (V) Masher 1 1 3 4 1 0 1 (VI) Masher 2 2 0 0 0 3 0 (VII) P Solar 1 1 1 1 0 3 (VIII) P Mech 1 0 0 0 0 6 (IX) Cherry coffee 0 1 0 0 0 0

Masher 1 = plate masher; Masher 2 = slotted cage masher – these products were stored as either green bean or dried split cherry; Mech = mechanical dryer (Pinhalense design); P = parchment coffee

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SOLAR-DRYER TRIALS SEASON 1: 2003/04 6*Nguyen Van Thuong, Ho Thi Phuoc, Tran Kim Loang, Ha Thi Mo

**Keith Chapman ***Anthony Marsh, John Michael Frank

Summary Two drying trials were conducted to compare the drying rates of 3 types of drying methods (a fan assisted solar drier, a naturally ventilated solar drier and patio drying) using 3 types of coffee product (fresh Robusta cherry, mashed Robusta cherry and Robusta parchment)

The two trials found that in cloudy or rainy conditions the use of solar dryers shortened the drying duration by one to two days compared to sun/open air-drying. In sunny and windy condition, the solar dryer systems did not shorten the drying duration in comparison with open air-drying. In each drying method trailed, dry mashed and parchment coffee took four to six days less to dry than cherry coffee. There was no observed difference in drying speed between mashed coffee and parchment coffee. Parchment coffee achieved the highest drying efficiency, (kg green bean /m2 /day) and cherry coffee achieved the lowest.

The risk of mould generation increases with the length of drying period. Among the three types of material compared (cherry, parchment and mashed coffee), mashed coffee had the highest risk of mould generation. Mechanical mucilage removers that cannot completely remove the mucilage layer of parchment coffee, create a possibility for mould generation.

Introduction The main reason for poor quality coffee and possible Ochratoxin A (OTA) generation occurs during the drying stage of the coffee processing. Slow and uneven drying and rewetting can result in mould generation and possible quality and OTA problems.

Presently there are three methods commonly used to reduce coffee bean moisture content to the required level of 12%.

• Open air sun drying • Mechanical drying • Solar drying

Open air sun drying and mechanical drying are popular methods in many coffee production countries in the world. Solar drying methods are not widely used as they are often more costly and complex to construct and manage.

Drying duration depends on many factors such as temperature, humidity, and thickness of material layer. Solar dryers (SD) can make more efficient use of sun energy, concentrate heat and avoid the risk of coffee being re-wet. It is therefore expected that solar drying will enable coffee to dry faster. The SD systems also allow the use of fans or air ventilation to speed up the coffee drying.

The type of coffee used for drying is also a factor in the drying speed. It is assumed that mashed/pulped and mucilage-removed coffee needs less time to be dry than cherry coffee.

The trials compared the drying efficiency between the SD system and open air sun drying, and of different types of coffee dried by the same method. The overall purpose of the trial work was

6*Post-Harvest Technology Department, Western Highlands Agro-forestry Scientific Technology Institute, (WASI) Boun Me Thout, Viet Nam ** Industrial Crops Officer FAO, Bangkok *** International Coffee Consultants

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to determine the most efficient way to make use of limited drying areas available to Vietnamese coffee farmers.

Objectives The objective of the trial was to assess the drying efficiency of two solar dryers (SD) and compare with the traditional drying on a concrete patio using three types of coffee material (fresh cherry, mashed and parchment).

Mould and OTA contamination risk using different types of coffee material under different drying methods was also assessed.

Methodology The trial consisted of nine treatments (3 methods of drying × 3 types of coffee materials). Three methods of drying were:

• (OA) Open air/patio drying: Coffee is dried in the open air during the day and covered with a canvas at night to avoid dew and rain.

• (NV-SD): Coffee is dried in the “green house” SD covered with transparent plastic, and two ends opened for natural ventilation.

• (FV-SD) Coffee is dried in the “green house” SD covered with transparent plastic, and two ends closed, applying fan ventilation during the day. The FV-SDs were vented every 2 hours for 5 minutes using a fan with air of flow of 3000 m3/ hour. The ventilation was made at 0700hr, 0900hr, 1100hr, 1300hr, 1500hr and 1700hr.

Three types of materials included:

• Fresh Robusta cherry coffee (C). • Mashed Robusta coffee (M). • Wet Robusta parchment coffee (P). Drying method Materials Treatment symbols

Cherry ( C ) OAC

Mash (M) OAM

Open air (OA)

Parchment (P) OAP

Cherry NVC

Mash NVM

Natural vented solar dryer (NV)

Parchment NVP

Cherry FVC

Mash FVM

Closed & fan vented solar dryer (FV)

Parchment FVP

Trial details • The area for each drying unit was 24 m2 (6 m x 4 m). • The starting quantity of material (cherry, mashed coffee or parchment) for drying was

720 g/treatment at 30 kg/m2 of product. • All treatments of drying coffee were raked 4 times/day • A sample-control plot of 1 m2 was used to dry 30 kg of cherry in the shade (covered with a

double-cloth net).

Timing of trials • Trial 1: 6/12/2003 - 25/12/2003 • Trial 2: 26/12/2003 - 9/1/2004

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• The trial was conducted at the Postharvest Research Center, WASI. • A Temporary Meteorology Station was installed within the trial site with measuring

instruments including a Digital Thermo hygrometer, Class A Evaporation Pan and Rain Gauge.

Solar dryers

Data collected Coffee data • Bean moisture content (M.C.) during drying days, • Mould generation, • Number of drying days until coffee moisture content reached 12%, • Drying efficiency (quantity of green bean / m2 / day). Environmental data • RH (%), air temperature, rainfall, total evaporation, • Variations of temperature and relative humidity (RH) for each drying method. Quality of coffee • Rate of defected beans (black, brown, mouldy) after drying, • OTA content, • Coffee cup quality.

Methodology • Variations of bean moisture content. Bean moisture content was measured every day for

both trials until it reached 12 M.C. Oven drying method for coffee moisture determination as per International Standard ISO 6673-1983: “Green Coffee – Determination of Loss in Mass at 105°C.”

• Air temperature (°C) and Relative Humidity (RH%) in the SDs were measured with a Digital Thermo hygrometer, (6 times/day at 0700hr, 0900hr, 1100hr, 1300hr, 1500hr, 1700hr).

• Temperature of the coffee mass was measured with a thermometer (6 times/day at 0700hr, 0900hr, 1100hr, 1300hr, 1500hr, and 1700hr).

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• Air temperature (°C) and Relative Humidity (RH%) outside the SD was collected from the meteorology station at the same time of measuring air temperature (°C) and relative humidity (RH%) in the trials units.

• Daily evaporation and rainfall measured by a Class A evaporation pan and rain gauge in accordance with standard weather monitoring procedures.

• Analysis of bean quality was in accordance with Vietnamese Standards. • Liquor quality was evaluated by cupping. • Mould occurrence and identification was conducted along guidelines provided by the FAO

specialist, Mick Frank.

Results and discussion Results

The results presented in Table 1 (Trial 1) shows that for the three drying methods, the air temperature in the FV-SD was higher than in the NV-SD and the open-air drying treatment (OA). The temperature achieved in the FV-SDs with parchment coffee was the highest (29.6°C). There is a large variation in temperature between the FV-SD and the NV-SD and OA (5 to 6°C).

Table 1. Average air temperature during the day (°C) for Trial 1 (6/12/2003-25/12/2003) Period Treatment

0700hr 0900hr 1100hr 1300hr 1500hr 1700hr Average °C

C 20.5 23.1 25.1 25.4 24.4 21.7 23.4 M 20.4 22.8 25.1 25.0 24.1 21.9 23.2 P 20.3 22.9 25.0 25.0 24.1 21.7 23.2

OA

Average 20.4 22.9 25.1 25.1 24.2 21.8 23.3 C 21.1 24.2 25.1 27.3 26.0 22.4 24.4 M 21.1 25.0 28.5 28.5 25.9 22.2 25.2 P 20.3 23.8 26.0 26.7 26.0 22.3 24.2

NV

Average 20.8 24.3 27.2 27.5 26.0 22.3 24.6 C 22.7 28.8 33.2 34.6 31.3 24.0 29.1 M 22.2 29.4 33.5 35.2 32.1 25.3 29.6 P 21.9 28.1 32.1 33.6 30.9 24.2 28.5

FV

Average 22.3 28.8 33.0 34.5 31.4 24.5 29.06

Generally the air temperature during the day in all treatments tended to increase gradually in the period between 0900hr and 1500hr in all three methods of drying. However, due to impact of the greenhouse effect, air temperature in the SD-FV during the period from 9.00 to 15.00 was the highest. See Graph 1.

Table 2. Daily average relative humidity (%) Trial 1 (6/12/2003-25/12/2003) Period Treatment

7.00 9.00 11.00 13.00 15.00 17.00 Average °C

C 87.5 74.6 66.0 64.1 66.7 76.8 72.7 M 88.2 76.5 66.2 65.5 69.0 77.1 73.8 P 88.2 75.8 66.9 65.5 68.7 77.1 73.7

OA

Average 88.0 75.6 66.4 65.1 68.1 77.0 73.4 C 83.4 65.9 55.5 55.4 61.3 72.6 65.7 M 83.5 68.6 56.7 57.3 64.8 75.6 67.8

NV

P 87.1 74.1 68.4 63.7 66.9 74.1 72.4

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Period Treatment 7.00 9.00 11.00 13.00 15.00 17.00

Average °C

Average 84.7 69.6 60.2 58.8 64.3 74.1 68.6 C 84.7 73.2 63.6 63.0 67.7 76.8 71.5 M 91.1 83.4 76.8 71.9 75.9 80.4 79.9 P 85.9 74.7 66.2 61.6 70.9 77.6 72.8

FV

Average 87.2 77.1 68.9 65.5 71.5 78.3 74.7

The result in Table 2 shows that RH tended to gradually reduce during the period from 0900hr to 1500hr. The highest RH achieved was in the FV-SD (74.7%), the next was in OA (73.4%) and the lowest was in NV-SD (68.6%). From 1700hr, the RH increased in all three drying methods because the open air temperature reduced and RH increased. See Graph 2.

Similar results were obtained through observation of daily temperature and relative humidity developments in Trial 2. See Graphs 3 and 4.

Discussion Normally the higher the drying temperature and the lower the RH, the shorter the drying process. High air temperature in closed FV-SDs made temperatures of bean bulk increase considerably, but high relative humidity FV-SD appeared to decrease the drying speed as moist air was not moved away from the coffee.

In addition, high temperature together with high humidity in FV-SD promoted the fermentation of coffee cherry/bean and affected the quality of final products.

It is difficult to control the relationship between temperature and relative humidity to keep temperature high but relative humidity low. It is expected that the use of fan ventilation in FV-SDs helps to reduce relative humidity. After each fan ventilation, the temperature and relative humidity in FV-SDs varied considerably.

Table 3 shows that the temperature and relative humidity in FV-SD reduced each time after fan ventilation. Relative humidity and temperature varied most in the period from 0900 to 1500hr. At 1700hr the air ventilation seemed to have no positive impact. It appeared to increase the relative humidity in SD by 2%. This is explained as follows:

At 0900hr to 1100hr due to the impact of “greenhouse effect”, heat accumulation made temperature in SDs increase higher than outside temperatures. The fan ventilation helped to reduce temperature in SDs. At 1700hr the outside temperature reduces while the relative humidity increases. Therefore, ventilation carried out at 1700hr of later will draw moist cool air into the SDs, causing an increase of the humidity in SDs. It is therefore recommended not to ventilate the FV-SD after 1700hr.

At 0700, the first fan ventilation of the day has positive impact as it reduces the relative humidity in SD by 5.3%. This is probably because the air temperature reduces and RH in SD increases over night because it is sealed. Condensation was found inside plastic roof. Therefore, the ventilation in early morning helps to remove condensation and reduce RH in SDs.

The air ventilation reduces both the air temperature and relative humidity and temperature at the surface and inside of coffee mass. The figures collected at 0900hr and 1100hr show that the temperature at the surface of coffee mass was reduced considerably while the temperature inside of coffee mass was not much reduced.

Similar results were obtained in Trial 2 with the same air ventilation time and fan capacity as Trial 1 (see Table 4).

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Table 3. Variation of temperature and air humidity in the fan-ventilated solar drier FV-SD. Trial 1: (6/12/2003 - 25/12/2003)

Period Treatment 07000 09 00 1100 1300 1500 1700

Average

T - TK 87.2 77.1 68.9 65.5 71.5 78.3 74.8 Relative humidity (%) S - TK 81.9 71.2 60.8 60.3 70.8 80.3 70.9 Difference -5.3 -5.9 -8.1 -5.2 -0.7 +2.0 -3.9

T - TK 22.3 28.8 33 34.5 31.4 24.5 29.1 Air temperature (°C) S - TK 21.7 25.7 29.7 29.4 26 24.4 26.2

Difference -0.6 -3.1 -3.3 -5.1 -5.4 -0.1 -2.9 T - TK

22.4 29.4 34.6 35.5 32.1 25.8 30.0 Temperature at surface of coffee mass (°C)

S - TK

22.1 27.6 32.7 32.5 28.4 25.3 28.1

Difference -0.3 -1.8 -1.9 -3.0 -3.7 -0.5 -1.9 T - TK 24.4 28 32.2 32.7 31.9 28.1 29.6 Temperature inside

coffee mass (°C) S - TK 23.6 27.9 31.7 32.2 29.9 28.8 29.0 Difference -0.8 -0.1 -0.5 -0.5 -2 +0.7 -0.6 Note: (+): increasing, (-): reducing, (T - TK): before ventilation, (S - TK): after ventilation Note that the use of fan ventilation in FV-SD at 1700hr in both trials increased the relative humidity but reduced temperature by only a small amount.

Table 4. Variation of temperature and air humidity in the fan-ventilated solar drier FV-SD. Trial 2: (26/12/2003 - 9/1/2004)

Period Treatment 0700 09 00 1100 1300 1500 1700

Average

T - TK 86.3 69.6 60.5 55.1 60.4 72.0 67.4 Relative humidity (%) S - TK 83.8 65.2 58.1 51.6 58.0 74.4 65.2

Difference - 2.5 - 4.4 - 2.4 -3.5 -2.4 + 2.4 -2.2 T - TK 21.2 29.3 35.2 37.4 33.2 25.2 30.3 Air temperature (°C) S - TK 21.0 27.9 31.1 33.3 29.4 24.0 27.8

Difference -0.2 -1.4 -4.1 -4.1 -3.8 -1.2 -2.5 T - TK 22.5 32.4 40.1 41.5 37.6 29.2 33.9 Temperature at surface

of coffee mass (°C) S - TK 22.5 31.2 38.3 40.6 35.2 27.8 32.6 Difference 0 -1.2 -1.8 -0.9 -2.4 -1.4 -1.3

T - TK 25.1 29.2 33.4 36.1 34.2 31.4 31.6 Temperature inside coffee mass (°C) S - TK 24.7 29.2 33.1 35.1 33.4 30.7 31.0 Difference -0.4 0 -0.3 -1.0 -0.8 -0.7 -1.6 Note: (+): increasing, (-): reducing, (T - TK): before ventilation, (S - TK): after ventilation The variations of coffee drying duration in the first trial are shown in Table 5. Coffee in all FV-SD treatments took less time to be dry than coffee in NV-SD and OA treatments. The mashed coffee treatments dried fastest and achieved 12% M.C. wb after 16 days of drying. Parchment coffee reached 12% M.C. wb after 16 to 17 days of drying; the cherry coffee took 19 to 21 days to achieve 12% M.C. Graphs 5, 6, and 7 show the moisture reduction versus time in Trial 1.

In Trial 2, the OAM treatment was dried as in the first trial but reached 11.1% M.C. after only 10 days and was faster than the NVM and FVM. The evaporation and rainfall were important factors in relation to this drying duration. Comparing the total net evaporation in the drying period for Trials 1 and 2, it was found that in Trial 1 the total net evaporation in 16 days was

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43.89 mm, (2.74mm/day) while in the Trial 2 the total net evaporation reached 35.49 mm in only 10 days (3.55mm/day).

Thus, in the Trial 2 with hot and sunny weather the temperature was high during the drying process and resulted in high evaporation and less time required for drying in the Trial 2 compared to Trial 1 (Table 6).

Table 5. Drying duration in Trial 1 (6/12/2003-25/12/2003) Coffee moisture content (% wb)

Treatment Before drying

After 16 days

drying

After 17 days

drying

After 18 days

drying

After 19 days

drying

Water amount (kg) in coffee lost after

16 days*

Total days of drying

C 61.4 22.1 20.3 18.2 16.0 362 21 M 60.6 12.2 397 16 P 56.2 13.4 11.0 356 17

OA

Av. 59.3 15.9 372 16 C 60.4 17.7 16.5 14.1 12.0 373 19 M 58.1 11.9 378 16 P 59.4 12.7 363 16.5

NV

Av. 59.3 14.1 372 16 C 61.4 16.0 15.5 13.7 11.5 389 19 M 60.9 11.1 403 15,5 P 57.4 12.0 371 16

FV

Av. 59.9 13.0 388 *Total net amount of evaporated from Class A pan in 16 days was 43.89mm, equivalent to 1053 L/24m2 of water surface area. Total rainfall in 16 days was 7.81mm, equivalent to 187.44 L/24m2. Table 6. Drying duration in Trial 2 (26/12/2003-9/1/2004)

Coffee moisture content (% wb)

Treatment Before drying

After 10 days

drying

After 11 days

drying

After 13 days

drying

After 15 days

drying

Water amount (kg) in coffee lost after 10

days *

Total days of drying

C 61.2 24.0 22.8 16.9 15.4 352.4 17 M 58.0 11.1 379.8 9.5 P 54.0 12.6 11.7 341.1 10.5

OA

Av. 57.7 15.9 358.1 C 61 23.5 22.3 17.5 14.0 352.9 16 M 58.0 12.5 10.5 374.4 10.5 P 54.0 13.1 10.5 338.9 10.5

NV

Av. 57.7 16.4 14.4 355.6 C 61.2 27.9 24.8 17.7 12.9 332.5 16 M 59.0 12.3 10.1 383.4 10.5 P 55.0 10.5 358 9.5

FV

Av. 58.0 16.9 359.6 *Total net amount of water evaporated from Class A pan in 10 days was 35.49 mm, equivalent to 851 litres/24m2of water surface area. Total rainfall in 10 days was 1,6 mm, equivalent to 38,4 litres/24m2.

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Table 7. Drying efficiency (Trials 1 and 2)

Treatment Quantity of products (kg) converted into clean bean coffee *

Total of drying days

Drying efficiency (kg of clean bean/m2 day)

C 319 38 0.35 M 361.9 25.5 0.59

OA

P 555.4 27.5 0.84 C 322.7 35.0 0.38 M 361.6 26.5 0.57

NV

P 356.3 27.0 0.86 C 331.8 35.0 0.40 M 338.4 26.0 0.57

FV

P 546.9 25.5 0.89 * Clean bean coffee with 12% M.C. wb Table 7 presents the average drying efficiency of the two trials. The drying efficiency of cherry and parchment coffee in NV and FV is obviously higher. In each method of drying, parchment coffee always achieved the highest efficiency of drying, the next is mashed coffee and cherry coffee achieved the lowest drying efficiency.

Coffee is a beverage product, thus it is therefore necessary to evaluate quality after drying. ISO 0470 procedures for coffee quality analysis were followed. In the results shown in Tables 8 and 9 most of the treatments had high proportions of black and brown beans. Coffee mashed with the Le Trung Chau masher had a higher rate of mouldy beans than coffee mashed with VINA masher. One of the reasons might be the masher of Le Trung Chau crushed and broke pulp and skin cells which contain nutrients and sugars and created a convenient medium for fungus to develop.

Table 42. Quality of clean bean coffee Proportion of defects in 300g of coffee bean (%) Materials

Brown bean Black bean Mouldy bean Total (%)

Cherry coffee 0.38 2.26 - 2.64 Mashed coffee I 0.64 2.30 0.06 3.00 Mashed coffee II 2.96 0.93 0.93 3.82 Parchment coffee 2.25 1.3 - 3.55

Table 43. Quality of coffee liquor

No Treatment methods Aroma Taste Overall 1 Parchment coffee (pulped and

mucilage removed by Robusta-600), mechanical drying (Pinhalense dryer)

Sweetly floral Typical Robusta, slightly pronounced acidity, good mouth feel

Very good quality

2 Parchment coffee (pulped and mucilage removed by Robusta-600), solar drying.

Less aroma Fair, moderately perceptible bland

Medium

3 Parchment coffee, drying on concrete patio (open air drying)

Clean, sweetly herbal

Typical Robusta, slightly perceptible acidity

Good

4 Mashed coffee (VINACAFE masher), Solar drying.

Mouldy odour with moderately pronounced level.

Taint with musty and fruity flavour. All cups unclean

Poor

5 Mashed coffee (Le Trung Chau masher), Solar drying.

Mouldy odour with moderately perceptible level.

Flavour varies in different cups: satisfied, hidey, mouldy, greenish

Poor

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No Treatment methods Aroma Taste Overall 6 Mashed coffee (Le Trung Chau

masher), drying on concrete patio Common Typical Robusta, a little bit

mixed flavour Poor to medium

7 Cherry coffee, solar drying Oniony, Fruity Over fermented, sour, unattractive

Poor, suitable for processing instant coffee

8 Cherry coffee drying on concrete barbecue

Moderate aroma, clean

Typical Robusta flavour Medium

Evaluated by: FCC – in HCMC The analysis of materials before drying also indicated a high proportion of overripe cherries (3.8%), unripe cherries (15%), dried cherries (3.5%). Ripe cherries only accounted for 75%.

The evaluation results of coffee of samples processed by different methods indicated that all types of solar-dried materials gave poorer flavour of beverage than mechanically dried parchment coffee (Table 43).

Parchment coffee for drying in SDs was processed by LXT-1500 machine of Thong Nhat Mechanical Company. Mucilage removal effectiveness of this machine is low, only reaching 51.7%. The remaining mucilage layer covering the parchment became fermented during the first stage of drying because of high temperatures and bean humidity and this has probably resulted in fermented flavours and mould growth. This is likely to be the reason for average quality of liquor coffee.

Flavour faults were also detected in cherry coffee. Parchment coffee dried on a concrete patio gave average to good beverage and had the typical flavour of Robusta coffee.

Mashed coffee gives unacceptable coffee beverage quality. It takes less time to dry mashed coffee than parchment and cherry coffee but due to fast mould generation in the early stage of drying, coffee beverage has a musty and earthy flavour. The risk of OTA contamination in this type of coffee is very high.

Research indicates that Ochratoxin A (OTA) is generated by specific fungi such as A. ochraceus, A. niger, A. carbonarius, Penicilium verucosum. Results from an analysis carried out by Plant Protection Section, WASI regarding status of mould contamination in parchment coffee in cherry samples before the two drying trials were carried out (Table 10), indicated that proportion of mould contamination in parchment coffee in the Trial 1 was higher than the Trial 2. Probability of Aspergillus spp. contamination was different among the collected cherry samples. More than 80 species of mould were identified in coffee bean samples after drying — 14 Aspergillus species and 4 Penicium species. The proportion of mould contaminated coffee beans and probability of Aspergillus contamination of the two drying trials are shown in Table 11. The result indicated that in all three drying methods in Trial 1, the proportion of mould contamination in mashed coffee material was approximately 100%. Mashing mixes coffee beans with pulp and broken pulp and this gives a good nutritional medium for many mould species to develop, therefore the risk of OTA mycotoxin generation is also high.

As there was considerable rain during Trial 1, mould contamination was higher in the OAP and OAC treatments than FV and NV treatments.

The proportion of mould contamination of beans in cherries is lower than that of beans in parchment and mashed coffee. This means that the method of drying coffee cherry in favourable conditions (Trial 2) will contribute to a reduced rate of mould contamination because the beans are protected by dry cherry skins. This outcome has changed the previous attitude, which stated, “As it took longer to dry coffee cherry, the risk of mould contamination would be higher”. In the trials the opposite was observed.

Generally the proportion of mould infected coffee beans during drying in Trial 2 was lower than Trial 1 and number of Aspergillus spp. existing in samples in the second trial was higher than that of the first trial.

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General observations from these trials The longer the drying, the higher the proportion of mould infected coffee found. Of three types of drying materials, mashed coffee had the highest mould infection rate in both trials followed by parchment coffee. The use of a mechanical mucilage remover that cannot completely remove the mucilage layer from parchment coffee contributes to mould generation risk.

Table 10. Mould contamination in parchment coffee in fresh cherry samples before drying Time of sample

taking Repeat Proportion of mould

contaminated parchment coffee

Aspergillus spp. contaminated

probability

No of Aspergillus spp. isolates existing in

samples 1 30.6 1/9 1 2 49.0 1/2.3 2 3 51.0 1/25 1

1st time

05/12/2003 Av. 45.3 1 68.8 1/3.3 3 2 32.8 1/8.5 2 3 75.7 1/54 1

2nd time

25/12/2003 Av. 59.1

Source: Plant Protection Department, WASI Table 11. Proportion of mould contaminated coffee beans and probability of being contaminated by Aspergillus spp. isolates

Proportion of mould contaminated coffee beans 10 days after transplanting (%)

Aspergillus spp. contaminated probability

1st time

Aspergillus spp. contaminated probability

2nd time Treatment

1st trial 2nd trial Probability Number of

Aspergillus spp. isolates existing

in sample Probability

Number of Aspergillus spp. isolates existing

in sample C 86.4 24.8 1/8.8 3 1/2.9 4 M 100.0 83.6 1/4.1 6 1/2.8 6 P 100.0 68.6 1/52.5 2 1/4.1 3

OA

Av. 95.5 59.0 C 70.0 36.4 1/9.2 4 1/3.2 5 M 98.6 68.6 1/5.0 4 1/2.6 6 P 88.8 69.3 1/14.2 1 1/5.2 5

NV

Av. 85.8 58.1 C 65.7 37.8 1/2.5 4 1/2.2 3 M 100.0 80.7 1/1.4 4 1/1.7 8 P 81.4 74.3 1/9.3 2 1/3.2 3

FV

Av. 82.4 64.3 Control sample 81.4 71.4 Source: Plant Protection Department, WASI

Conclusion and recommendations Conclusions 1. In cloudy or rainy conditions, the use of polythene tunnel solar dryers can shorten coffee

drying duration by 1 to 2 days compared to sun/open air drying. In sunny and windy conditions, the solar dryer systems do not shorten the drying duration in comparison with

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open air drying. Anaheim style driers, while being more expensive, use continuous fan operation to dry parchment coffee in 3 to 4 days. Anaheim Driers also have a smaller enclosed air volume, which should be tested by making the polythene tunnels much lower.

2. For each drying method it took 4 to 6 days less under the prevailing weather conditions to dry mashed and parchment coffee than to dry cherry coffee. There was no observed difference in drying speed between mashed coffee and parchment coffee.

3. Parchment coffee achieved the highest drying efficiency of 0.84 to 0.89 kg/m2/day and cherry coffee achieved the lowest at 0.35 to 0.40 kg/m2/ day.

4. The risk of mould generation increases with a longer drying period. 5. Of the three types of material compared (cherry, parchment and mashed coffee), mashed

coffee had the highest risk of mould generation. 6. The use of mechanical mucilage removers that cannot completely remove the mucilage

layer of parchment coffee, had the potential to generate mould. 7. Dried coffee cherries gave beans with better appearance than parchment coffee in the trials.

Mashed coffee gave beans with the most mixed colours. 8. Parchment coffee dried by solar dryers gave average quality of beverage/liquor coffee.

Cherry coffee gave beverage coffee with the sour flavour of fermented pulp. 9. Mashed coffee gave a mixed and bad flavour including mouldy, fruity and earthy flavours. 10. Cherry coffee had a fermented fruity flavour.

Recommendations 1. Additional trials using more frequent fan ventilation and continuous ventilation between the

hours of 0700 to 1700 should be carried out. 2. For parchment coffee, additional trials should be carried out on the number of times of

raking and thickness of coffee layer in solar dryers. 3. Mashers should not be recommended for coffee processing. Mashed coffee dries faster, but

the risk of mould and Ochratoxin A generation is extremely high. 4. The trial should be repeated for Arabica coffee in order to determine whether there are any

factors that affect the quality of coffee beverage dried by solar driers.

Graph 1. Variations of temperature means in 3 drying units (drying period 12.12.2003 -25.12.2003)

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Graph 2. Variations of relative humidity (%) in dryer units (drying period 6.12.2003 -25.12.2003)

Graph 3. Variations in temperature means in 3 dryer units (drying period 26.12.2003 -09.1.2004)

Graph 4. Variations of relative humidity means (%) in 3 dryer units (drying period 26.12.2003 -09.1.2004)

Graph 5. Variations in moisture content of whole cherry in Trial 1 (drying period 6.12.2003 -25.12.2003)

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Graph 6. Variations in moisture content of mashed coffee in Trial 1 (drying period 6.12.2003 - 25.12.2003)

Graph 7. Variations in moisture content of parchment in Trial 1 (drying period 6.12.2003 - 25.12.2003)

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SOLAR DRYING TRIALS SEASON 2: 2004/05 7* Nguyen Van Thuong, Ho Thi Phuoc

** Keith Chapman *** Anthony Marsh

Summary During the 2004/05 coffee season, trials were conducted to compare the drying efficiency of simple solar dryers with standard open-air patio drying of Robusta cherry, Robusta parchment and Arabica parchment.

Under cloudy conditions, a simple, naturally ventilated solar dryer was found to have approximately 6% higher drying efficiency per m2 than conventional open-air drying on a concrete patio. An intermittently operated fan to periodically ventilate the solar dryer improved the drying efficiency of the solar drier over the open-air patio drying by approximately 12%.

Under sunny and windy conditions, the concrete patio was found to have approximately 10% higher drying efficiency than the naturally ventilated and fan ventilated solar dryers. There was little difference between the two solar dryers under sunny and windy conditions.

The liquor quality of coffees dried on open-air cement patios and in solar dryers, was not significantly different. For Robusta coffee, drying parchment coffee gave better liquor quality than drying cherry coffee. Cherry coffee gave more fruity flavoured cups, while parchment coffee gave cleaner cups.

Introduction Coffee quality, mould development and possible OTA contamination are influenced by moisture and the drying procedures. In Viet Nam during peak harvest, slow drying, and re-wetting of coffee is often experienced due to limited drying patio areas.

In 2003/2004, solar drying tests were carried out at the Western Highlands Agro-Forestry Science and Technical Institute (WASI). For Robusta parchment coffee drying, the results showed that the fan ventilated solar dryer (SD) system, (a tunnel covered with clear polythene and using fan ventilation) had a higher drying efficiency than a natural ventilated solar dryer and drying on a cement patio (drying efficiencies were 0.89, 0.86 and 0.84 kg green bean/m2/day respectively). In each drying method the drying efficiency of parchment coffee was the highest, followed by mashed coffee and then cherry coffee which gave the lowest efficiency of drying. Efficiencies for green bean kg/m2/day were: fan ventilated SD — 0.35, natural ventilated SD — 0.38, and drying on a cement patio/open air — 0.40.

Some changes in the 2003/04 SD (solar drier) design were made for the 2004/2005 trials.

• The height of the SD polythene tunnel was reduced to1.2 m (instead of 2 m as in the 2003/04 trial) to reduce the volume of air in the SD.

• The fan was placed near the ground surface to increase air removal of the boundary layer of air over the surface of coffee layer.

• The ventilation system was changed to two fans at one end of the SD and the opening at the opposite end was 10 cm above the ground to encourage air movement across the coffee surface.

7 *Postharvest Technology Department, Western Highlands Agro-forestry and Technological Institute, (WASI) Boun Me Thout, Viet Nam **Industrial Crops Officer FAO, Bangkok ***International Coffee Consultant

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Objectives The objectives of the second season of drying trials were to compare the efficiency of the modified green house tunnel style solar dryers with the normal drying on cement patios, for Robusta and Arabica wet parchment coffee and fresh Robusta cherry coffee.

Processing coffee and cacao

Methodology Trials conducted The three drying methods were tested.

• OA: Open air-drying on a cement patio during the day and covered with a plastic tarpaulin sheet at night to avoid dew and rain.

• NV-SD: Drying in the green house tunnel 1.2 m high, covered in transparent polyethylene film. Both ends were closed with small section near the roof open for natural ventilation.

• FV-SD: Drying in the green house tunnel 1.2 m high, covered in transparent polyethylene film with fan ventilation (FV-SD) with a ventilation capacity of 12.6 m3/minute. The fan-blade diameter was 250 mm, electricity consumption capacity was 40 Watt (220 Volt). Two fans were supplied for each drier and located 10 cm above the ground at one end of the drier. A small gap of 10 cm was left across the base at the opposite end to draw air across the coffee. SD ventilation was conducted as 0600hr, 0900hr, 1200hr, 1500hr for 30 minutes each time.

Three drying trials used these coffees.

• Arabica parchment with pulp and mucilage mechanically removed. • Trial 1 was conducted from 30 October 2004 – 11 November 2004 using 2 drying

systems of FV-SD and OA. • Robusta parchment coffee with pulp and mucilage mechanically removed.

• Trial 2 was conducted from 18 November 2004 – 4 December 2004 using FV-SD, NV-SD and OA drying systems.

• Fresh Robusta cherry coffee. • Trial 3 was conducted from 5 December 2004 – 19 December 2004 using FV-SD, NV-

SD and OA.

Trial implementation • The trials were conducted at the WASI coffee processing area in Boun Me Thout. • A temporary meteorology station was installed at the trial location. This included a micro

data logger for automatic measurement of temperature and relative humidity, a hygro-thermometer, Class A Evaporation Pan for evaporation measurement and a rain gauge for monitoring rainfall.

• The FV-SD fan ventilation was operated in daytime and left sealed overnight. • During the first 5 days, all trials were raked every 30 minutes for parchment coffee, and

from day 6 onward raking was done 6 times/day. For cherry coffee, raking was done 6 times/day (at 0800hr, 1000hr, 1200hr, 1300hr, 1500hr, 1700hr).

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• Drying area for each treatment was 24 m2 = 6 m x 4 m. The trial plots were 2 m apart and placed 6 m from the boundary wall of the drying area.

• The amount of coffee material in each trial plot was 720 kg (24 m2 x 30 kg/ m2). • Cherry material for all trials had 5% unripe cherries, 2% ripe cherry (calculated by mass). • Equipment in the meteorological station was used in accordance with the manufacturer’s

guidelines.

Data collected • Quality of coffee used (% by weight: unripe cherry, overripe cherry, foreign matter) was

assessed by taking a 1 kg sample and classifying various types of cherries. Each type was weighed and the percentage calculated.

• Efficiency of drying method was calculated at kg bean /m2/day. • Analysis of bean quality from parchment coffee and bean from cherry coffee was conducted

after drying; 300 g from each sample (from 5 points in the test plot and mixed with each other). Percentage of brown, black, fermented and mouldy beans was calculated by mass.

• Bean moisture samples were taken daily and determined by using the standard ISO oven-test method.

• Climatic data from the test site were collected: • Humidity and temperature were measured with a micro-data logger, • Water evaporation was measured by an Class A evaporation pan, • Daily rainfall was measured by a rain gauge.

• Number of drying days from commencement of drying until the bean moisture reached 12% M.C. were noted by regular testing of moisture content of sub-samples.

• Quality of coffee liquor was evaluated by cup tasting at CAFĒCONTROL, Buon Me Thout. • Mould infections present in samples were identified by the Plant Protection Department of

WASI.

Results and discussion Temperature and air relative humidity High temperature, low relative humidity, a large surface area of coffee and high wind speed will tend to speed up the drying process. It is assumed in the fan-ventilated SD, air will be heated inside by the “green house” effect, and the fan system is used to pull the hot air across the coffee surface and away from the coffee to the outside air. This exchanged the warm humid air inside with cooler drier air from outside.

Temperature observations during the coffee drying trials showed that temperatures in the FV-SD were higher than in the NV-SD and OA drying.

• On hot sunny days the FV-SD unit was 6 to 8°C higher than the corresponding OA unit and 1 to 3°C hotter than the corresponding NV-SD unit.

• On average during the whole drying process, the temperature in FV-SD was 3.7°C higher than OA and 1°C higher than the NV SD.

• The higher the temperature in SD units the lower the relative humidity. On average, relative humidity in FV-SD was lower, at 58.25%, than OA at 72.56% and NV at 69.08%. See Tables 1 and 2.

The results in Tables 3, 4 and 5 show that the air temperature during daytime in all drying methods tended to increase in the period from 0900hr to 1500hr irrespective of cloudy or sunny weather conditions. Due to the “green house effect”, the air temperature from 0900hr to 1500hr in FV-SD was the highest, then NV-SD and lowest, OA. On rainy days, temperature in FV-SD was 2.5°C and 0.5°C higher than in OA and SD-NV respectively. In sunny days FV-SD was higher than OA (4.5°C) and the SD-NV (0.7°C).

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Relative humidity in solar dryers in either rainy or sunny conditions tends to develop conversely. RH in FV-SD was lower than in NV-SD and in OA. See Table 4 and Table 6.

Thus, SD units are able increase temperature, reduce R.H. and shorten drying duration. Also, SD units reduce the risk of coffee being re-wet and the resulting mould contamination that can affect the quality of the final bean coffee.

Trial 1: Drying Robusta parchment coffee from 18 November 2004 to 4 December 2004 Table 1. Average air temperature during drying days (0600hr to 1800hrs) (°C)

Treatment days > 1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 Average OA 29.21 28.54 27.86 24.08 24.04 25.28 23.82 29.02 25.21 27.09 23.35 25.11 27.38 25.52 24.92 26.03 NV-SD 29.44 30.46 31.51 26.90 26.50 28.22 25.95 32.92 27.22 32.11 25.17 30.53 31.44 28.81 24.01 28.74 FV-SD 31.49 31.04 31.48 27.39 26.81 29.01 26.45 33.95 27.85 33.12 30.67 31.44 32.68 29.69 24.49 29.84

Trial 2: Drying Robusta parchment coffee from 18 November 2004 – 4 December 2004 Table 2. Average relative humidity during drying days (0600hrs to 1800hrs) (%RH)

Treatment days > 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average OA 57.71 53.31 49.71 71.61 74.35 80.93 92.51 69.23 84.30 76.52 87.63 67.20 63.37 74.97 85.10 72.56 NV-SD 63.76 58.87 52.25 70.04 70.82 74.54 85.49 63.63 78.34 63.20 82.71 59.73 56.15 65.98 90.75 69.08 FV-SD 53.37 49.37 41.80 60.55 62.0 64.84 76.68 52.69 68.93 52.27 73.83 48.57 43.81 55.01 70.08 58.25

Trial 2: Drying Robusta parchment coffee from 18 November 2004 – 4 December 2004 Table 3. Change in air temperature (°C) in the three drying units on a cloudy day* (24 Nov 2004) Treatment Time

06.00 07.00 08.00 09.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 Average

OA 21.72 24.23 23.18 24.25 24.93 24.98 24.57 24.76 24.92 24.70 23.78 22.84 22.60 23.97 NV-SD 22.17 23.71 24.60 26.44 28.15 28.54 28.02 28.89 28.33 27.34 25.16 23.48 22.93 25.98 FV-SD 22.43 24.15 25.06 27.14 28.69 29.35 28.61 29.46 29.0 27.78 25.48 23.67 22.98 26.45 *0.09mm of evaporation from Class A pan and 2.29mm of rain on this day Trial 2: Drying Robusta parchment coffee from 18 November 2004 – 4 December 2004 Table 4. Change in relative humidity (%RH) in the three drying units on a cloudy day* (24.11.2004) Treatment Time

06.00 07.00 08.00 09.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 Average

OA 100 97.18 94.72 89.07 86.38 87.15 92.05 92.06 89.74 89.08 91.75 96.18 97.3 92.51 NV-SD 98.88 94.51 89.77 83.62 78.12 75.47 79.59 77.62 77.90 79.07 86.15 93.59 96.13 85.42 FV-SD 95.03 86.23 86.29 73.01 66.81 64.62 65.23 66.98 68.05 69.63 78.64 87.28 90.22 76.77 *0.09mm of evaporation from Class A pan and 2.29mm of rain on this day Trial 2: Drying Robusta parchment coffee from 18 November 2004 – 4 December 2004 Table 5. Change in air temperature (°C) in three drying units during a sunny day* (29.11.2004) Treatment 06.00 07.00 08.00 09.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 Average OA 20.89 22.80 25.61 27.00 28.28 28.77 30.22 32.02 30.22 31.42 29.49 22.49 21.28 26.96 NV-SD 22.48 24.33 29.44 32.12 34.43 35.29 37.83 40.3 36.43 33.48 29.88 22.47 20.30 30.67 FV-SD 20.82 25.46 30.13 32.76 36.29 37.22 39.68 41.87 37.51 34.23 29.34 22.71 20.83 31.45 *2.55mm evaporation from Class A pan on this day

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Trial 2: Drying Robusta parchment coffee from 18/11/2004 - 4/12/2004 Table 6. Change in relative humidity (%RH) in three drying units during a sunny day* (29.11.2004) Treatment 06.00 07.00 08.00 09.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 Average OA 95.58 74.87 71.83 67.21 69.95 61.43 55.73 49.5 54.70 51.78 57.35 82.29 89.42 67.81 NV-SD 98.14 80.95 62.65 54.36 46.64 46.10 39.71 33.58 39.9 47.29 56.91 79.21 91.05 59.73 FV-SD 91.45 69.09 50.6 41.93 32.62 31.54 24.87 19.16 26.77 34.79 48.64 75.43 85.42 48.64 *2.55mm evaporation from class A pan on this day

Drying conditions Trial 1: Drying Arabica parchment coffee Trial 1 (Arabica). Conditions were warm, dry and windy and parchment dried more quickly in open air (see Table 12).

Trial 2 (Robusta parchment coffee). Coffee in FV-SD dried most quickly (Table 7).

Trial 3 (Robusta cherry coffee). Conditions were sunny and hot (Table 8).

Trial 2: Drying Robusta parchment coffee 18.11.2004 to 4.12.2004 To achieve moisture content of 12% in FV-SD needed only 14.5 days of drying while the NV-SD required 15.5 days and 16.5 days for open air drying (OA). During Trial 2 the weather was dull and overcast with a number of rain days during the trial. The evaporated water for 16 days of drying was 44.96 mm equivalent to 1079.04 L/24m2. Total rainfall in 16 days was 22.81mm, equivalent to 547.44 L/24m2.

Table 7. Duration of drying Robusta parchment coffee

Coffee moisture content (%wb) Treatment Before drying

After 10 days

After 14 days

After 15 days

After 16 days

*Water (L) in coffee lost after

15 days

Total days of drying

OA 59.4 31.80 20.65 16.5 13.60 318 16.5 NV-SD 59.4 28.76 18.70 14.5 12.00 328 15.5 FV-SD 59.4 24.69 12.60 10.09 Dry 347 14.5 Note: Total amount of evaporated water during a period of 16 days was 44.96ml, equivalent to 1079.04 L/24m2. Total rainfall in 16 days was 22.81 mm, equivalent to 547.44 L/24m2

Trial 3: Drying Robusta cherry coffee (5 to 19 December 2004) Total rainfall in 14 days was only 0.19 mm, equivalent to 4.56 L/24m2; while the total amount of evaporated water in 14 days was 50.97 mm, equivalent to 1223.28 L/24m2 (Table 54). Thus, Trial 3 (Robusta cherry coffee) conducted in dry, windy weather and higher air temperatures, the OA treatment (coffee drying on concrete patio in open air) dried most rapidly. In Trial 3, despite higher temperatures and lower RH in the SD units, the drying speed was 1 to1.5 days slower than for OA. The drying speed in the FV-SD unit with fan operation showed little difference with the NV-SD unit under the dry windy conditions. It appears that in Trial 3, natural airflow without the restriction of SD units gave the best drying result.

Table 8. Duration of drying cherry coffee

Coffee moisture (% wb) Treatment Before drying

After 10 days

After 14 days

After 15 days

*Water amount (L) in coffee lost

after 14 days

Total days of drying

OA 60.50 27.80 11.00 Dry 400 14 NV-SD 60.00 33.53 15.76 12.53 378 15.3 FV-SD 60.00 30.83 14.36 11.43 384 15 Note: Total amount of evaporated water during a period of 14 days was 50.97ml, equivalent to 1223.28 L/24m2. Total rainfall in 14 days was 0.19 mm, equivalent to 4.56 L/24m2

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Quality of green bean Analysis of green bean coffee quality showed that in all 3 trials there were no mouldy beans. In the Trial 2 with Robusta parchment coffee, the product had the highest percentage of fermented and black beans because it had rained for many days during the drying trial. In the open-air drying method (AO) a tarpaulin was used to cover the coffee during rain periods. Covering appears to have increased temperature and humidity of the bean bulk mass and promoted fermentation processes. The use of LXT-1500 machine for pulping and mucilage removal resulted in a lot of mucilage left on the parchment. (Reported by Nguyen Van Thuong and Phan Thanh Binh (2004) on coffee processing equipment). This also appears to have contributed to a high proportion of fermented beans (6.35%) in the OA test unit for Trial 2. For Trial 1 (Arabica parchment) coffee and Trial 3 (Robusta cherry), both in warm dry weather conditions, the coffee beans had fine colour and a small percentage of black and fermented beans was small (see Table 9).

Table 9. Coffee bean quality

Percentage of defect beans in 300 g of coffee bean identified by eye

Trials

Black bean Fermented bean Mouldy bean

Total

Trial 1 Arabica parchment coffee

0.08

1.25

0

1.33

Trial 2 Robusta parchment coffee

1.88

6.35

0

8.23

Trial3 Robusta cherry coffee

0.52

1.76

0

2.28

Status of mould contamination in coffee beans The analysis of mould contaminated coffee beans is shown in Table 10. A detailed analysis of fungi in the coffee is given in the following paper, “Effects of Processing Alternatives on Development of Fungi in Coffee”.

For Trial 1 (Arabica parchment), before drying, the percentage of mould contaminated beans was 83% but after drying this was reduced to 30 to 35%. Trial 2 (Robusta parchment) had a high percentage of mould contaminated beans (63 to 0%) both before and after drying. The LXT-1500 machine of Thong Nhat Mechanical Company was used to prepare parchment coffee from both Arabica and Robusta for Trial 1 and 2. According to the report by Nguyen Van Thuong and Phan Thanh Binh (2004) on coffee processing equipment, the LXT-1500 could remove mucilage efficiently from Arabica (89.2%), but when this machine was used for processing Robusta it could only remove 57.5% of the mucilage. Robusta parchment in Trial 2 with mucilage not fully removed is the possible reason for high proportion of mould contamination coffee found in Trial 2.

For Trial 3 (Robusta cherry) before drying, the cherry coffee had 100% of mould contaminated beans. After drying, the cherry coffee had the highest percentage of beans contaminated by species that generate Ochratoxin A including A. niger and A. carbonarius (7 to 20%). It appears that pulp and mucilage removal before drying may contribute to reduced mould potential

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Table 10. Proportion of coffee beans contaminated by mould species (%) Black Aspergilli group Ochre

Aspergilli group

Flavi Aspergilli group

All species

A. niger

A. carbonarius

A. japonicus

A. ochraceus

A. Flavus

A. Oryzae Pe

nicil

lium

sp

p.

Others

Before drying 83 2 0 0 0 0 0 43 83 After drying in FV-SD 35 1 0 0 0 1 0 2 35

Trial 1 Arabica parchment coffee After drying

under OA 30 2 0 0 0 0 0 0 36

Before drying 73 0 0 0 1 0 0 5 127 After drying in FV-SD 63 0 0 0 0 3 0 2 94

After drying in NV-SD 89 0 0 0 1 0 0 1 156

Trial 2 Robusta parchment coffee

After drying under OA 90 1 0 0 1 0 0 1 58

Before drying 100 2 0 0 0 0 0 2 109 After drying in FV-SD 86 61 20 0 0 3 0 1 34

After drying in NV-SD 45 27 7 0 1 0 0 0 24

Trial 3 Robusta cherry coffee

After drying under OA 35 27 14 0 1 1 0 0 28

Source: Plant Protection Department, WASI

Coffee cup quality In general, parchment coffee (both Arabica and Robusta, Trials 1 and 2) gave a coffee liquor with soft, fragrant flavour and balanced odour. Robusta cherry coffee (Trial 3) from NV-SD unit gave a fragrant, clean, delicious liquor quality with typical Robusta flavour. Cherry coffee drying from the OA unit and the FV- SD unit gave average to fair liquor quality with a little fruity fermented odour (Table 11).

Table 11. Results of coffee cup quality

Treatments Aroma Flavour Assessment OA Soft fragrant, clean Balanced, clean, with good flavour Good Trial 1

Arabica parchment coffee

FV Fragrant, delicious, clean Balanced, clean, with good flavour Good

OA Fragrant, clean Typical Robusta, clean Good NV Fragrant, clean Typical Robusta, clean Good

Trial 2 Robusta parchment coffee FV Fragrant, clean Typical Robusta, clean Good

OA Fragrant with a little fruity fermented odour

Typical Robusta mixed with fruity flavour

Average

NV Fragrant, clean Typical Robusta, clean, delicious Good

Trial 3 Robusta cherry coffee

FV Fragrant with a little fruity odour

Typical Robusta Fair

Drying efficiencies Weather conditions at the time of each trial impacted on each trial’s drying efficiency. Each trial also used a different coffee material and there was no replication of any of the trials due to time constraints, so comparison between results of each of the trials is difficult.

As a general observation, Trial 1 and 3 were conducted under similar hot dry conditions. Trial 1 with Arabica parchment gave the highest drying efficiencies, while Trial 3 Robusta cherry give the lowest drying efficiencies. Trial 2 gave drying efficiencies in the mid range.

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It appears that the effectiveness of Solar Drier units is very dependent on the prevailing weather conditions and the way the fan ventilation is used. However it is clear that for drying parchment coffee (Arabica or Robusta), a solar drier is much more efficient in the use of a given drying area and gives higher drying efficiency of green bean/m2/day compared to open air drying.

In Table 12, each 24 m2 Drying Unit was loaded with 30kg/m2 of coffee material. Trial 3: Fresh Robusta cherry, Trial 2: Demucilaged Robusta parchment and Trial 1: Demucilaged Arabia parchment.

Table 12. Drying efficiencies for drying units over 3 trials

Treatments Mean drying days Drying efficiency (Kg of clean green bean)

kg / day / m2 Trial 1 Arabica parchment coffee

OA

11

1.14

FV 12 1.04 Trial 2 Robusta parchment coffee

OA

16.5

0.70

NV 15.5 0.74 FV 14.6 0.79 Trial 3 Robusta cherry coffee

OA

14

0.52

NV 15.3 0.47 FV 15 0.48 Note: Trial 1 and Trial 3 occurred during periods of fine, dry weather with relatively windy conditions. This resulted in the OA (open air drying) giving greater drying efficiencies than the Solar Dryers FV-SD and NV-SD. Trial 2 occurred during a period of wet and overcast conditions, where the FV-SD gave the best drying efficiency.

Conclusions and recommendations Conclusions 1. Simple polythene tunnel solar dryers can increase and concentrate heat better than a cement

patio. 2. In overcast weather with rain or cloud, the solar dryers with fan/ventilator shortened the

Robusta coffee drying duration by 2 days compared to drying on concrete patio and 1 day compared to natural ventilated solar dryers. (Trial 2 Robusta parchment).

3. Under sunny and windy conditions the solar dryer systems did not shorten the drying duration in comparison with drying on concrete barbecue (Trial 1 and 3, Arabica parchment coffee and Robusta cherry coffee).

4. The locally made LXT-1500 pulper demucilager cannot completely remove the mucilage layer of Robusta parchment coffee and creates a risk of mould generation under some drying situations.

5. Liquor quality of coffees dried on open-air cement patios and in solar dryers, is not significantly different.

6. For Robusta coffee, drying as parchment coffee gives better liquor quality compared to drying as cherry coffee.

7. Cherry coffee often gives fruity flavour cups, while parchment coffee gives clean cups.

Recommendations 1. Farmer field trials should be planned to further evaluate wet processing methods that

remove the coffee pulp and mucilage layer to improve drying efficiencies. Other trials suggest that the VINACAFE pulper/demucilager is the best value unit currently available.

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2. In wet and cloudy conditions, simple solar dryer systems have potential to improve coffee drying efficiencies. Further farmer field trials are recommended to test acceptance by farmers.

3. Further trial replications should be made with solar dryers and these design changes: • Use a raised bed / drying tray above the concrete surface to facilitate the air ventilation

up and through the drying coffee. • Reduce the height of the roof of the drier. • Improve fan design to create better air-flow over and through the coffee. • Link fan operation to RH and temperature buildup in the SD unit, or continuously

operate fans during sunshine hours.

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EFFECTS OF PROCESSING ALTERNATIVES AND DRYING METHODS ON DEVELOPMENT OF FUNGI IN COFFEE

8*Tran Kim Loang, Ha Thi Mao et al. **John Michael Frank

Summary This paper summarises the fungal data for the previous paper, “Solar Drying Trials Season 2: 2004/05”. Bean infection was dominated by fungi other than members of Aspergillus, Penicillium and Fusarium. It was noted that these fungi tended to persist in the dried product, an aspect not commonly recorded in studies conducted elsewhere.

The two trials conducted in the 2003/4 season were demonstrably different in terms of drying dynamics where the slower drying trial showed a higher overall infection rate. However, it was in the second faster drying trial, that the toxigenic A. carbonarius reached its highest numbers.

Niger Aspergilli were apparently less prevalent in the trials of both seasons, and the numerical significance of other fungi, greater than is usual in studies conducted in other producer countries. A. carbonarius in particular, was more prevalent than expected, especially in the 2003/4 season, but caution must be exercised in this because distribution studies have indicated this species to be characteristically common in few locales and virtually absent in the vast majority of others.

The niger group, and A. carbonarius, were more prevalent in cherry processing of whole and mashed cherry but mashed cherry was more prone to high infection rates than whole cherries.

Unlike the pre-drying processing, there was little or no effect between fan ventilated parabolic solar dryers, solar dryers naturally ventilated or open air drying on cement terraces, on the fungal community outcome.

Wet processing depressed infection of Niger Aspergilli but not overall infection rates.

Ochre Aspergilli were found in low numbers at or around the detection limit. This means that no conclusion could be drawn about the impact of the processing variations tested on this important OTA-producer.

Introduction Coffee processing begins with harvest and ends with the completion of drying. The objective of these operations, which have many variations around the coffee world, is to stabilize the food component of the fruit – the coffee bean. Pre-drying processing varies widely and may consist of no preparation, may only involve sorting of fruit or may include methods to remove all fruit tissues. Fungi are a part of the fruit and seed biology and can cause spoilage and mycotoxin production so any investigation relating to the usefulness of a processing method must include an evaluation of its affect on fungal development.

Dryness limits the development of microorganisms and even some insects, by keeping water activity (Aw, a measure of water availability) under the threshold for their growth. According to the species, fungi stop growing between an Aw of 0.93 and 0.7. OTA cannot be produced below an Aw of 0.80. Just as importantly, as water availability falls, the relative success of the different fungi commonly found in coffee changes, so rare species can become common and common species become rare. Several species that can cause spoilage and OTA production are more adapted to the intermediate conditions of partially dried coffee.

8 *Plant Protection Department - Western Highlands Agro-forestry Scientific and Technical Institute (WASI) ** International Consultants

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OTA production is not adequately predicted by occurrence of toxigenic species. Presence of OTA producers is, of course, a pre-condition of its production but there are too many intervening factors for this relation to be reliable. Biomass would provide a better predictive parameter, but the available methods for the mycological analysis measure frequency and not biomass. However, frequency does have some utility. We are entitled to assume that, for comparison, there is some quantitative relationship between these two measures such that increasing frequency implies increasing biomass and that a higher frequency implies a higher biomass.

Sun and mechanical drying are common methods used in Vietnamese coffee production. Sun-drying coffee takes a long time whereas it is rarely possible for small-scale farmers to afford mechanical dryers. On the other hand, it is frequently raining during coffee harvesting in some regions of the Western Highlands and often the farmer does not allocate a sufficient area for drying. Field surveys have indicated loading in excess of 60 kg/m2 is common, as against an approximate optimal loading of 25 to 30 kg/m2. A cheap method of pre-drying processing that can reduce drying time, in effect increasing the capacity of available drying facilities, may well improve quality by reducing the opportunity for spoilage and OTA production during drying, especially during the period when the coffee is partly dried.

In this report, some results of mycological analyses of solar driers trials on coffee (2003/2004 & 2004/2005) carried out by Postharvest Department of WASI are introduced.

Methodology Experimental set-up In the 2003/4 season, studies were conducted to evaluate the interaction of drying method and pre-drying processing. Cherry coffee, mashed cherry and de-pulped coffee (parchment) were dried using three different methods giving a total of nine treatments:

FV = Drying in solar drier with fan ventilation

NV = Drying in solar drier with natural ventilation

OA = Sun drying on concrete patio

The coffee was placed in wooden frames of 2 m x 1 m x 7 cm at a loading rate of 30 kg/m2. The coffee was sampled daily for moisture parameter measurement and other relevant physical parameters and was turned by raking four times daily. There were two trials run in the 2003/4 season: 06 to 25/12/03 and 26/12/03 to 09/01/04

in the 2004/5, the emphasis was adjusted to accommodate Arabica processing and evaluate the possible efficacy of Robusta parchment production. Here trials were carried out with three coffee processes: Arabica parchment, Robusta parchment and Robusta cherry for reference.

Arabica parchments were dried by two methods:

• Drying in solar drier with fan ventilation

• Sun drying on concrete patio

Robusta coffee (parchment and cherry) were dried by three methods:

• Drying in solar drier with fan ventilation

• Drying in solar drier with natural ventilation

• Sun drying on concrete patio

Mycological methods Sampling Ten samples were randomly selected from the pile of freshly harvested cherries, mixed into a batch and dried to < 12 % M.C. Ten samples were then randomly selected from this batch for

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use in the trials. Daily samples for the determination of Aw and moisture content were similarly collected.

Isolation of fungi Fungi were counted and isolated by the methods found in this handbook9. Samples comprised either 70 beans from 70 fresh fruits or 70 beans from a kilo of dry cherry after hulling. Beans were surface sterilized for 10 minutes with 1% hypochlorite before rinsing in sterile water, blotting and plating 7 beans per plate of DG18 medium. If the analysis was of fresh coffee, the parchments were first freed from mucilage using 0.05% NaOH. Incubation was conducted at room temperature (22 to 28°C). Counts and isolations, where more detailed taxonomic work was required, were conducted on days 5 and 10 after plating. The results were expressed as:

• Bean infection rate (%, normalized on number of beans),

• Community composition (proportion, normalized on number of fungi),

• Probability of occurrence (average number of beans required to find a taxon).

Results and discussion Processing trials of 2003/4 The context for interpreting the mycological changes lies in the nature of the pre-drying processing and the time-course of drying. Tables 1 and 2 show two different criteria for characterizing the drying time-course.

Table 1 shows that differences in the drying rate between treatments are less than those between runs. This is consistent with findings in several other producer countries that demonstrate that sun and solar-assisted drying is most affected by the prevailing meteorological conditions above normal treatment variations (extremely high loading rates, eg. 50kg/m2, can also have a major affect). The total evaporation potential for drying cherry coffee was 53 mm ± 6% for the two runs and for parchment and split cherry 38 mm ± 6% evaporation potential was required. The required evaporation potential was accumulated more quickly in the second run.

Table 2 gives a more common method of evaluating drying efficacy – number of days required to achieve dryness (here defined as below 13% M.C.). The two methods together show that cherry drying at its maximum is comparable to that of parchment and mashed cherry, but that drying requires more time. This is due to cherry coffee being wetter initially, drying more slowly in the first 12 to 48 hours and drying more slowly from 25% to dryness.

During the slow drying run (1st), the drying rates of the solar dryers were as good or better than that of the traditional cement surface drying but generally was no better than equal to cement in the open air under the better drying conditions of the second run. This demonstrates how drying methods interact with the drying conditions – the best method varies according to drying conditions.

9 Handbook of Mycological Methods, Enhancement of Coffee Quality Project. FAO GCP/INT/743/CFC. Frank, J.M., 2001.

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Table 1. Collation of maximum drying rates (between day 2 and 11) for the processing Trials 2003/4

C M P C M P 1st Run 2nd Run OA -2.8 -3.4 -3.3 -5 -6.9 -5.1 NV -3.4 -4 -3.8 -4.9 -4.2 -5.1 FV -3 -4.1 -3.5 -4 -6.4 -5.4

C=cherry coffee; M=mashed cherry; P=parchment; OA=open air on cement; NV=parabolicos dryer with ‘natural’ ventilation; FV=parabolicos with periodic fan ventilation Table 2. Collation of the number of days required to reach <13% M.C. (wb) for the processing Trials 2003/4

C M P C M P 1st run 2nd run OA >20 17 18 >15 9 10 NV 20 17 17 >15 10 11 FV 20 17 18 15 10 9

C=cherry coffee; M=mashed cherry; P=parchment; OA=open air on cement; NV=parabolicos dryer with ‘natural’ ventilation; FV=parabolicos with periodic fan ventilation Figure 1 illustrates these points for cherry drying. In the slower time-course (1st run), the data points fall below the best fit relation at day 12 making the slope of the initial 12 days steeper and the points from day 15 to 20 flatter than the best fit relation as the line approaches 25% M.C. In the better conditions of the 2nd run, the methods’ drying rate falls together – both methods flatten about equally and there is little difference in drying times.

Figure 1. Drying time-courses of two runs of cherry drying on cement and in parabolicos solar dryers. The curves are 2nd order polynomials and since there is clearly no difference in run 2, only the cement surface regression is shown.

The differences in drying times between treatment extremes – about a week (Figure 2), has not produced consistent differences in fungal development in previous studies. Even though the treatments have a bearing on the outcome by affecting drying time, we would not expect

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dramatic outcomes. In general, one might expect more fungal development where drying is slower as in cherry drying on cement. However, the structural integrity of the cherry skin acts as a barrier to the introduction of exterior fungi to the bean during processing whereas the cherry mashing process introduces saprophytes from the fruit surface to the moist and nutritious tissues of the mucilage and could produce a burst of growth. If this growth is by a mesophilic fungus adapted to the coffee bean, infection may occur.

Figure 2. Drying time-course means of three drying methods for all pre-drying procedures for both runs. OA=open air; NV=natural ventilation of parabolicos; FV=fan ventilation of parabolicos and two solar drying arrangements)

Conditions of temperature and humidity during the two processing trials were similar, despite demonstrable differences in drying rates, with about the same amount of water in the air producing slightly lower relative humidity in the warmer air temperatures of the second run (26 December 2003 to 9 January 2004).

Coffee bean infection The following fungi were isolated from the surface-sterilized beans in these trials:

• Black aspergilli: A. niger complex (could include A. tubingensis, awamori, others, A. carbonarius

• Ochre aspergilli: A. ochraceus and allies • Flavi aspergilli: A. flavus, A. parasiticus • Penicillium spp. • Some other fungi: Cladosporum spp., Eurotium spp., Fusarium spp., Rhizopus spp., and

unidentified fungi. Quantitatively, the infection rate of the coffee processed in the first run tended to be somewhat higher in the slower drying conditions. This could also have been due to a higher infection rate of the fresh cherries, but this information is not available.

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Figure 3. Fungal infection rates in dry coffee as a percent of beans with one or more infections

Cherries tend to have a lower infection rate than parchment and mashed cherries. The numerical differences between the different drying treatments are not large enough to be considered significant, nor are the relative differences here consistent. Overall infection rate in these trials was unaffected by the method of drying, but the pre-drying processing does seem to exert an influence. The largest difference is between the two runs, contributed by the ‘other fungi’, but it is not possible to confidently attribute this to the longer drying period as noted above since it could also be ascribed to different initial conditions that are not reported.

Robusta coffee is particularly associated with Niger Aspergilli but here, as figure 4 shows, it is usually found in less than 30% of beans. The mashed cherry in the first run is heavily infected but, based on Robusta cherry intensively analyzed from many other producer countries, not remarkably so.

Of more concern, because of its greater toxigenic potential, is the frequency of A. carbonarius. It is less common in the first run and in parchment preparations but the high levels attained in the mashed cherry of the second run suggests that the conditions imposed by this process can be suitable to its development. The fungus can be confidently identified because of the unique character of its conidiospore. However, it must be diagnosed by a compound microscope to credibly identify this species. The only ochre Aspergilli reported in these studies were also isolated from the mashed cherry treatment dried in the solar dryers.

Another way to judge the affect of the treatments on the fungal development is to focus on the fugal community. In this approach the absolute infection is not significant, rather the ability of a given taxon to succeed, although relative success may correspond to different levels of absolute success as is represented by infection frequency. Each run of these experiments share a set of initial conditions, so within each run, the comparison is valid.

Once again the main emerging pattern is that the two runs are different, with A. carbonarius much more prominent in the second run, except in parchment. Since the second run has one set of initial conditions and given appropriate initial conditions, the clear implication is that A. carbonarius can be favoured in cherry drying variations over parchment drying. The drying methods tested do not alter this picture.

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% infected beansSolar / fan

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Figure 4: Bean infection rates after drying for A. niger, A. carbonarius and all other taxa. Ochre and Flavi Aspergilli and Penicillium spp. occurred irregularly in small numbers, ochre restricted to the second run (mashed cherries)

Regarding the drying methods, it appears that the fan ventilated solar dryer suited the niger Aspergilli, including A. carbonarius, more than the other fungi. Why this should be, given that the drying dynamics are all but identical in the two solar dryers, is difficult to rationalize.

OTA and other mycotoxins are not uniformly distributed in the particles of a sample; rather they are at relatively high levels in a very few of the particles. The frequency of OTA producers should exceed that of OTA since a certain threshold of growth is required in addition to its presence. The average number of particles in which one bean is expected to be infected is given for the important toxigen, A. carbonarius in table 4. It was below detection limit in the freshly harvested beans.

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Table 3. Characterisation of the significance / dominance of A. carbonarius and non-carbonarius Niger Aspergilli in the fungal communities infecting beans. The proportion is based on the total fungi isolated so is unconnected to infection rate*

1st run 2nd run CH PARCH MASH CH PARCH MASH niger carbon niger carbon niger carbon niger carbon niger carbon niger carbon FV 0.37 0.08 0.11 0 0.69 0 0.15 0.53 0.28 0 0.15 0.60 NV 0.1 0.02 0.05 0 0.17 0.07 0.08 0.28 0.18 0.04 0.09 0.34 OA 0.07 0.08 0.02 0 0.21 0.03 0.12 0.38 0.18 0.08 0.12 0.43

One toxigen in every 3 to 5 beans, as it is in several of the treatments, is very high. This test should de done on the coffee for OTA. Fairly high OTA levels can correspond to low infection rates, but the high likelihood of presence is a useful guide to directing a costly analytical programme.

Table 4. Probability of A. carbonarius after the action of treatments in the processing trials of 2003/04.

1st run (06/12/03 - 25/12/03) 2nd run (26/12/03 - 09/01/04) After drying After drying Drying

methods Before drying C P M Av.

Before drying C P M Av.

Parabolicos w/ fan 17.5 0 0 52.5 4.7 0 2.0 4.2

Parabolicos 64.2 0 10.7 27.5 8.6 28.0 4.3 7.8 Sun dry (concrete)

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Average 0 20.8 0 22.0 0 6.3 32.3 2.8

Processing trials of 2004/5 Figures 5, 6 and 7 give the infection rates of fungi infecting beans in the processing trials of 2004/5 which compares Robusta cherry processing, the predominant practice in Viet Nam, with wet processing of Robusta and Arabica. Because of the number of treatments being investigated, it was not possible to run the different processes concurrently which introduces an additional level of uncertainty in the interpretation.

Broadly speaking, the results are consistent with the previous season’s experiments in that the ‘other fungi’ tended to dominate in all conditions. This has not been the case in studies in the eight other producers that have conducted processing trials or surveys. The total infection (‘all species’) is calculated based on the number of clean beans and never exceeds 100%, whereas beans can be doubly or trebly (or more) infected, so the sum of infection of all infections can exceed the infection rate as can be seen in the Robusta parchment.

The pattern suggests, as before, niger group Aspergilli are more adapted to cherry processing than to wet processing. Based on the previous year’s work, this is also true of the cherry processing variation of splitting or mashing the fruit before drying. Ochre Aspergilli were recorded at or around the detection limit in four of the samples so no information on the effect of the processing treatments on this important group can be gathered. It is notable that other fungi are prominent. Usually no fungi, apart from mesophilic and xerophilic fungi, persist in similar numbers at the end of processing or at the beginning as was found here.

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Figure 5, 6 and 7. Infection rates of various taxa in the processing trials of the 2004-5 season. Arabica parchment was not dried in the solar dryer with natural ventilation

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COFFEE QUALITY AND OCHRATOXIN A (OTA) FARMER SURVEY (2003/2004)

10*Le Anh Tuan, Bach Than Tuan et al. **Tran Kim Loang, Ha Thi Mo, et al.

***John M. Frank, Anthony Marsh ****Keith Chapman

Summary Based on an analysis of survey responses, we propose the following actions.

1. Initiate a programme of training courses aimed at improving postharvest practices in order to prevent mould growth in coffee.

2. Produce a good practices policy specifically adapted for Vietnamese coffee production. 3. Introduce a programme that would help farmers to acquire mechanical dryers and other

equipment such as pulpers / splitters, moisture meters to increase control of coffee processing.

4. Devise a market-led strategy of premiums offered for the application of good practices based on a certification programme.

Typical farm processing conditions

Introduction The Technical Co-operation Project seeks to improve the quality and safety of Vietnamese coffee production. An essential part of developing practical advice that can be implemented is a knowledge of what is currently done and why. The farmer tries to make a success of his operation which means he is aware of problems and potential problems and responds to them. His experience is a good guide to what aspects require attention for improvement. This information also provides the basis for adapting the research results for maximum relevance and effective implementation.

The ability to conduct surveys is an essential skill for responsible national and local institutions for regulation and improvement of the sector. Aiding the VN coffee institutions to gain this skill is also entirely consistent with the purpose of TCPs.

10 * CAFECONTROL, Daklak and HCMC ** Plant Protection Department - Western Highlands Agro-forestry Scientific and Technical Institute (WASI) *** International Consultants **** Industrial Crops Officer FAO Bangkok Thailand

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The survey was conducted between 1 February 2003 and 30 April 2004 in six districts of Daklak province which was recently separated into two provinces, Daklak and Daknong.

No. District Average Altitude (m)

Coffee Area (ha) Villages

1 CöMgar 514,15 34.990 Cö Sue, Eapok, Quang Tien, Quang Phu, Ea Kpam, Ea Hding, Ea Kiet, Cö Dlie Mnong, Ea tul, CöorÑang, Ea Dröng.

2 Krong Buk 698,25 34.265 Cö Bao, Binh Thuan, Thong Nhat, Ea Blang, Ñoan Ket, Pông Prang, Ea ngai, Chö Kpoâ, Cö Pông, Cö ne.

3 Krong Pak 545,7 16.113 Hoa Ñong, Ea Knuec, Ea Xong, Ea Kenh, Hoa An, Hoa Tien, Ea Uy, Tan Tien, Ea phe, Krong Buk, Phuoc An.

4 Krong Ana 500,55 19.640 Ea Na, Buon Trap, Ea Bong, Binh Hoa, Hoa Hiep, Ea Bhok, Ea Tien, Ea Ktur.

5 Buon ma Thuot City 481,7 11.240

Ea Tam, Thanh Nhat, Tan Loi, Tan Tien, Tan An, Ea Tu, Hoa Thuan, Khanh Xuan, Hoa Thang, Tan Hoa, Tuï An, Tan Thanh.

6 Dakmil 697,1 19.178 Thuan An, Dak lao, DakRla, Dakgaên, Ñuc Manh, Daêk Sac, Dakmil.

Methodology • A team was chosen from CAFECONTROL, Daklak for the survey. • Information was collected by interview at each farm guided by a questionnaire. • Interview 20 householders in each district, selected randomly. • One 500 g sample of dried coffee taken at each householder. • Moisture and quality determination each sample. • Transfer samples to WASI for microbiological and toxin tests. • Information is collated and analysed for the report.

Results and discussion The results are presented and discussed under six headings:

1. Farm information. 2. Harvesting conditions and production of each householder. 3. Processing conditions of each householder. 4. Summary of mycological analysis 5. Storage conditions. 6. Technical problems – farmers’ perspective.

1. Farm information Table 1. General information on coffee farms in six districts of Viet Nam

Intercrop with coffee? (%)

Electricity used in farms? (%)

Farmers live on farm? (%) No. District

Average area/ householder

(ha) Yes No Yes No Yes No CöMgar 1.8 25 75 5 95 35 65 Krong Buk 2.8 15 85 20 80 20 80 Krong Pak 1.2 10 90 5 95 5 95 Dakmil 3.3 30 70 5 95 0 100 Krong Ana 2.3 30 70 20 80 20 80 Buon ma

Thuot 1.2 70 30 50 50 40 60

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Average 2.1 30 70 17.5 82.5 20 80 => Chart 1, interpretation:

• Average area of each farm is 2.1 ha. The largest is in Dakmil district 3.3 ha/householder, the lowest is in Buon Me Thuot 1.2 ha/householder.

• 30% of households intercrop fruit trees with coffee. Major species: pepper, durian, avocado.

• Percentage of farmers who use electricity is low: 17.5%. • Only 20% of farmers live on farm. Reasons given are lack of available services and

infrastructure such as schools, hospitals, electricity and labour / employment.

2. Harvesting and Production Table 2. Production and harvesting practices in six districts of Viet Nam

CöMgar Krong Buk

Krong Pak Dakmil Krong

Ana Buon

Ma Thuot

Avg.

Area (ha) of coffee 1.6 2.8 1.2 3.1 2.3 1.2 2.0 Fresh cherries 25.6 34.7 19.9 38.4 39.2 15.6 28.9

Raw green bean 5.8 8.2 4.2 8.4 8.6 3.5 6.45

Production (MT) Rate of

fresh cherries / raw green bean

4.4 4.2 4.8 4.6 4.6 4.5 4.5

Begin 10 10 10 12 11 11 Harvesting period (month) End 12 12 1 1 12 12

Green 21.9 34.3 30.9 30.0 29.8 33.0 30.0 Ripe 72.3 62.0 67.3 70.0 70.3 67.0 68.2

Rate of cherries (%) Overripe 5.9 3.8 1.9 0 0 0 1.9

Selective picking 5.6 9.8 12.6 18.2 12.0 10.7 11.5 Method of

harvest (%) Strip picking 94.4 90.2 87.4 81.8 88.0 89.3 88.5

Number of times of harvest

2.5 2.8 2.9 2.2 2.2 2.3 2.5

Quality of harvest / person/day 192.0 199.3 178.0 201.5 197.0 141.0 184.8

=> Chart 2, interpretation: • Average coffee area of a farm is 2 ha. The majority coffee trees were planted between

1985 and 1995; some areas planted between 1968 and 1969 (Dakmil, Buon Me Thuot City); some areas planted recently between and 1999 and 2000 (Krongbuk).

• Average fresh cherries production: 28.9 MT / farm. • Average coffee raw green bean: 6.5 MT / farm. • Average rate of fresh cherries / raw green bean: 4.5 / 1. This varies between regions, the

highest is Krong Buk district (4.2 / 1), the lowest is Krong Pak (4.8 / 1). • Average yield 3.25 MT green coffee / ha. • Harvesting season often begins in October, ending in January. Earliest harvest is districts

CöMgar, Krong Buk, Krong Pak (October), the latest harvest is Dakmil (December).

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• The rate of green cherries in harvesting is rather high at an average of 30% of harvested cherries. The highest is Krong Puk (34.3%), the lowest is CöMgar (21.9%).

• Little green cherry is harvested early because farmers use selective harvesting methods since cherries are not yet ripe en mass. When this occurs, strip picking is used because of labour shortages and security concerns, consequently the proportion of green cherries is higher than in early harvest.

• Harvesting by selective picking at early harvest season accounts for an average 11.5% of the total. Dakmil is the highest at 18.2% and CöMgar is the lowest at 5.6%.

• All farmers know that a high rate of green cherries will lead to a fall in coffee quality and specifically causes the dark bean (dark colour, flat, wrinkled).

3. Coffee processing practice Table 3a. Pre-drying handling of cherries (fresh cherry was not sorted by any farmer surveyed)

CöMgar Krong Buk

Krong Pak Dakmil Krong

Ana Buon Ma

Thuot Avg

days 4.7 9.6 11.6 6.2 6.5 6.0 7.4 Delay of processing % farms 35.0 70.0 50.0 50.0 65.0 50.0 53.3 Farm-terrace transport (km) 2.8 3.1 2.8 5.4 4.4 3.2 3.6

CH* 95.5 66.2 64.2 83.5 85 83.7 79.7 Processing forms (%) SPL 4.5 33.8 35.8 16.5 15 16.4 20.3 *CH = cherry processing; SPL = split cherry or parchment processing => We can see in table 3a:

• No farmers separate floats or immature cherry, or remove foreign matter before processing because there is no labour available and no price incentive to do so.

• At present, a significant proportion of farmers delay the start of drying of fresh coffee cherry for an average of 7 days. The reason given is a lack of space on the drying yard, the perception that it does no harm and because it is thought to dry faster.

• Fresh cherry is kept in PP sacks or in heaps during this delay until the pulp shows signs of rotting.

• Average distance for transportation of coffee after harvest from farm to drying yard is 3.6 km. The greatest average distance is in Dakmil (5.4 km), the smallest average distance is in CöMgar and Krong Pak (2.8 km).

• Throughout the survey almost all farmers followed dry processing technology, drying either as whole cherry or as split cherry.

• Whole cherry drying accounts for 79.7% total production of the crop with the highest proportion in CöMgar (95.5%) and the lowest in Krong Pak (64.2%).

• Split cherry drying is used at early harvest crop when the volume harvested is smaller, labour is available and to compensate for the poor weather of that season. Also the faster drying means the farmer receives a quick income, which he needs to pay his urgent debts or living expenses.

• Almost all farmers think that the whole cherry method requires more time for drying, more labour but appearance of bean is better; split cherry method dries faster, less labour but colour of bean is uneven and the beans are frequently damaged by the pulping machine. They are known to be susceptible to turning black, mouldy or fermented in poor drying weather.

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Table 3b. Management parameters of the drying yard

CöMgar K’ Buk K’ Pak Dak Mil

Kring Ana

B’ Me Thuot Avg.

Concrete 60.0 28.0 93.5 40.6 69.8 58.5 58.4 Earth 36.0 71.0 6.5 52.0 20.4 29.5 35.9 Drying surface

(%) Tarpaulin 4.0 1.0 0.0 7.4 9.8 12 5.7

Area of drying yard (m2) 247.0 380.0 225.0 480.5 427.0 198.5 326.3 Pulped 4.3 3.6 4.6 4.8 5.4 4.4 4.5 Layer thick-

ness (cm) Whole 11.2 18.4 8 16.4 13.5 10.6 13.0 Pulped 16.9 14.4 18.8 20.5 21.6 18.0 18.4 Cherry loading

(kg/m2) Whole 68.0 102.9 50.8 93.2 81.0 61.2 76.2 Raking times / day 4.9 4.1 5.4 3.2 4.2 4.1 4.3

Whole 10.8 16.7 7.5 15.6 11.7 8.5 11.8 Drying duration (days) Pulped 5.2 4.1 3.2 4.0 3.0 4.0 3.9

Shaking 20.0 5.0 10.0 0.0 0.0 0.0 5.8 Biting 80.0 95.0 85.0 100.0 95.0 100.0 92.5

Method of determining dried coffee (%) Other 0.0 0.0 5.0 0.0 5.0 0.0 1.7

12% 10.0 0 5.0 0 0 0 2.5 13% 35.0 15.0 25.0 55.0 15.0 25.0 28.3 14% 35.0 50.0 30.0 45.0 50.0 0 35.0

Target moisture content

Other 20.0 35.0 40.0 0 35.0 75.0 34.2 Average moisture of coffee samples collected % 12.3 12.5 12.8 12.8 12.4 12.2 12.5

Farmers who manage drying (%) 95 100 100 95 100 95 97,5

=> We can see in Table 3b:

• Concrete is the most common drying surface at 58.4% in all districts with Krong Pak highest at 93.5% and Krong Buk the lowest at 28%.

• Earth is second most common drying surface at 35.9% with Krong Buk highest at 71% and Krong Pak lowest at 6.5%.

• Use of tarpaulin as a drying surface is unusual with an average of only 5.7% with Buon Me Thuot City highest at 12% and virtually no use in Krong Pak.

• The average drying yard is 326.3 m2 / farm in which the highest is Dakmil at 480.5 m2 / farm and Buon Me Thuot City lowest at 198.5 m2 / farm.

• Number of times of raking per day 4.3 / day (average). • Duration of drying fresh whole cherry was said by farmers to average 11.8 days. • Pulped cherry was said to dry in only about 4 days. • About 93% of farmers use the biting method for estimating dryness of coffee beans. • Farmers do not have a good knowledge of recommended moisture levels required for

safe storage since 69.2% thought that M.C. > 13% was satisfactory. • Average moisture of collected samples was 12.5% representing coffee that was stored 3

– 4 months. Since new-crop coffee can lose 1% M.C. in the first month of storage in VN conditions, the moisture of coffee before storage must be over 14%.

• When selling coffee, moisture must be 13% so farmers think that moisture of coffee to be stored should be over 13%, and after a time of storage moisture will be gradually decreased and will meet necessary moisture when selling i.e. 13%.

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Table 3c. Analysis of drying yard demands based on reported mean values of production and management parameters of the yards

CöMgar Krong Buk Krong Pak Dak Mil Kring Ana Buon Ma

Thuot Avg.

Yard area 247 380 225 480.5 427 198.5 326.3 Orchard area 1.6 2.8 1.2 3.1 2.3 1.2 2 Fresh CH 25.6 34.7 19.9 38.4 39.2 15.6 28.9 Green coffee 5.8 8.2 4.2 8.4 8.6 3.5 6.45 Drying period 10.8 16.7 7.5 15.6 11.7 8.5 11.8 Yard provision m2/ha 154.4 135.7 187.5 155.0 185.7 165.4 163.2

Cherry burden CH/m2 104 91 88 80 92 79 89

Minimum season* (days drying) 37.3 50.8 22.1 41.6 35.8 22.3 34.8

Minimum number of runs* 3.5 3.0 2.9 2.7 3.1 2.6 3.0

*These are calculated based on the recommended loading rate of 30 kg/m2 of fresh cherry and total utilization of the area of the terrace. => We can see in Table 3c:

• Seasonal burden on the drying yard varies around 90 kg/m2. The area provided by the farmers for drying may be sufficient in many countries where average yields are 750 kg/ha but here the average is over 3 tones/ha and the yards are too small, even based on the optimistic drying times recorded in table 3b. These figures suggest that harvest must be done in 3 to 4 passes with almost full utilization of the yard at the recommended loading of 30 kg/m2. This figure would rapidly climb if the drying times proved to be under-estimated as seems probable in some cases. In any case, the assumptions behind the calculations represents a ‘best-case scenario’ so a few weeks of inclement weather over the harvest season would produce real problems in managing the processing.

4. Summary of mycological analysis Niger complex species of Aspergillus infect 60% of beans on average. A. carbonarius, if the identification has been done carefully, is remarkably common, appearing in around 65% of all samples often at a high frequency. This is very different from all other nations yet studied so it needs to be confirmed as a matter of urgency since this species’ capacity for OTA production is high.

Ochre Aspergilli are found regularly in 20 to 25% of samples with only one instance of its infection rate exceeding 10%. This is a typical picture of the distribution of this fungus in Robusta cherry.

Table 4. Means of the Mycological and OTA analysis by district

mean +'ve* >10 >70 max min CöM’Gar district niger 64 20 20 7 107 17 carb 26 16 14 63 6 ochre 1 3 0 1 1 OTA 1 4 5 0 Krong Buk district

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mean +'ve* >10 >70 max min niger 50 20 20 3 113 17 carb 23 18 13 46 4 ochre 4 3 0 7 1 OTA 1 4 6 0 Krong Pak district niger 67 20 20 9 106 36 carb 24 18 15 62 7 ochre 1 8 0 3 1 OTA 1 2 5 0 Dakmil district niger 61 20 20 5 84 32 carb 22 18 13 45 7 ochre 2 6 0 4 1 OTA 1 2 5 0 Krong Ana district niger 70 20 20 10 121 33 carb 28 15 14 56 5 ochre 4 5 1 17 1 OTA 0 2 2 0 Buon Ma Thuot city niger 62 20 20 6 107 19 carb 16 18 9 44 6 ochre 2 3 0 3 1 OTA 1 4 3 1 *OTA analysis was conducted using the Vicam fluorimetric method. A validation exercise using a proportion of these samples and an HPLC method indicated there to be a 60% over-estimate in positive samples. The numbers in the table have been re-calculated using this factor. => We can see in Table 4: Comparing Krong Buk with Krong Pak, the former district has only 28% cement drying yards while almost 94% of farmers of the latter use cement surfaces. Krong Buk also has the worst drying yard provision and Krong Pak the best but the cherry burden (Table 3c) of the two are comparable. However, the reported drying time requirement in Krong Buk, at almost 17 days, is 2.5 times longer than Krong Pak so the minimum season length (a measure of the total amount of time the drying yard is in use) is much higher in Krong Buk – the coffee spends much more time on a soil drying yard than the coffee of Krong Pak does on cement.

Krong Buk shows the lowest niger infection rate of the study and is also low in ochre infection. It shows slightly more OTA positive samples, with the same mean and maximum, but these numbers are very uncertain given that they are low and subject to the problem of false positives. It appears, measured by these parameters, that soil is not a more problematic surface than cement. The same may be said for conformance to several other recommended practices usually considered to be important in controlling coffee quality and safety. Of course it is possible that many undesirable outcomes may have been avoided by the non-presence of OTA-producers or the presence of strong competitive pressure from other saprophytic fungi. If the latter is the case it may explain the lower niger infection since we have observed these species to be repressed by strong yeast growth. Evidence for this might be contained in cupping results with the expectation of more cup defects in the Krong Buk coffee than Krong Pak.

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Of course there are other parameters that could affect these figures but overall there is little in the quality parameters of fungal infection and OTA occurrence to separate the districts. This could be interpreted as meaning that processing parameters within the practices as described in the tables have little consistent impact on OTA occurrence. A more detailed analysis based on the individual farms might be more informative but this approach must be tempered by an appreciation of high variability of single sample analyses.

5. Coffee storage Table 5. On-farm storage of coffee

CöMgar K’ Buk K’ Pak Dakmil Krong Ana

B’ Ma Thuot

Avg.

Selling fresh cherry (%)

No No No No No No No

Farmers recognize ‘mouldy’ (%)

85 100 100 90 90 85 91.7

Own 60 90 95 95 100 65 84.2 Hulling machine (%) Hire 40 10 5 5 0 35 15.8

Sell 52.6 42.7 43.7 50.3 56.5 41.7 47.9 Green coffee (%) Store 47.4 57.3 56.3 49.7 43.5 58.3 52.1

Farmers (%) 5 10 25 65 10 20 22.5 Dry cherry

duration (d) 120 105 60 33.8 45 37.5 66.9

=> We can see in table 5:

• Few farmers store dry cherry because this will take much space in warehouse and is inconvenient for selling when necessary.

• 22.5% of all farmers surveyed store dry cherry; this is most common in Dakmil at 65% but only 5% of farmers in CöMgar store their dry crop.

• Those that store coffee do so for an average duration of 67 days. The longest is CöMgar, averaging 120 days, and the shortest, Dakmil at 34 days.

• Almost all of the farmers manage their processing and storage (97.5%) and over 90% recognise moulds or mouldiness.

• Just over half of on-farm storage is as green coffee (52.1%), a practice most common in Buon Ma Thuot city at 58.3%, the lowest is Krong Ana 43.5%.

6. Technical problems – farmers’ perspective During the interview the farmer was asked what he saw as his biggest problems in any area of his work whether plant pest and disease, horticultural issues, management or financial problems.

• The main processing method is the dry method so drying is the most problematic and decisive factor for the success of processing procedure.

• Farmers generally do not have mechanical drying so rely on sun-drying. Harvest (October to January) begins in most places during the last months of rainy season and this causes problems at the drying yard and consequent problems of coffee quality.

• Drying surface area is too small for the volume of coffee at peak of harvest. • Typically there is insufficient labour available during the harvest period. • Coffee stealing from the orchard is a problem and this induces farmers to harvest too

early bringing in green cherry.

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Conclusions a. Farm situation

• Average area of farm is 2.1 ha in which 2 ha are for coffee. This proves that coffee farmers have specialized to grow coffee and are dependant on the coffee sector economy for their welfare.

• Most farmers do not live at the farm because it is often far from population centres in areas lacking infrastructure such as schools, electricity and hospitals.

• High yields averaging 3.25 MTS (green coffee)/ha proves that farmers’ investment and cultivation skills are both very high.

• Fresh coffee cherry is brought to farmer’s house or drying yard daily and processing is conducted by the farmer.

b. Harvest situation • Coffee is harvested 2.5 times / crop. Labour supply for harvest is reported to be

insufficient. • Selective picking ripe cherry is carried out only at the beginning of crop harvest (11.5%

production) later harvesting is by strip picking amounting to 88.5% of production. • The rate of green cherry is quite high at an average of 30%. According to the Viet Nam

standard 10 TCVN95-88 (Standard of Viet Nam Coffee Industry) this kind of raw coffee is rated Grade 4 (lowest grade).

• If excessive green cherry is harvested, this reduces the yield and also produces an uneven moisture distribution in the bulk coffee. These beans retain high moisture after hulling and often become mouldy.

c. Processing situation • Harvested coffee cherry is never cleaned or sorted (eg. into immature, dried, ripe) before

drying. Foreign matter in the drying layer might be expected to cause extra microbial contamination.

• There is no price incentive to expend more effort during processing despite it being known that coffee quality is affected by these cherry characteristics.

• Delaying drying after harvest (in sacks and heaps) for excessive periods is widespread. The guideline is for a delay of a maximum of 2 days but approximately 50% of farmers average 7.4 days delay. This causes heating and fermented / mouldy taste.

• There is every indication that drying yard provision is inadequate for the yield of coffee and this may explain the excessive delay before drying.

• About 80% of the VN coffee is dried as whole cherry, the balance being pulped or split cherry.

• Drying period of the split/pulped cherry is reported to be much shorter than whole cherry but the frequency of damaged and darkened beans is often high. The pulping machine also produces a mixture of forms of coffee such as split cherry, whole cherry, bean in parchment, naked bean and pulp and this causes a product with uneven moisture content.

• The split/pulped coffee is also more susceptible than whole cherry to damage by poor weather and if dried mechanically the exposed beans can become black.

• It is noted that mould still develops in the coffee mass where there are wetter beans, such as immature cherries, even in good drying weather.

• The pattern of mould infection and OTA presence in the different regions is rather uniform although processing conditions, particularly between Krong Buk and Krong Puk, vary greatly. This is not reflected in the measurements made of fungal development.

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d. Drying yards • Some 36% of farmers dry coffee on bare earth and another 8% use tarpaulin. • Though there is no indication in the data that drying on bare earth leads to a deterioration

of safety in the coffee, data was not available to evaluate the contention that coffee will have stinker, earthy, mouldy and fermented defects when dried on earth. Rain during drying on earth is clearly problematic.

• Average drying area 326.3 m2 for 28.9 MTS fresh cherry. • Seasonal loading of the fresh cherry on the drying yard is 76.2 kg/m2 and the estimated

drying period is 12 days. • Seasonal loading for pulped/split cherry averages 18.4 kg/m2 and the estimated drying

period is just over 4 days. • Overall the drying parameters for whole cherry revealed by the survey are not acceptable.

Our survey carried out in 1990s found that drying 22 kgs/m2 on concrete surface required 25 to 30 days to reduce M.C. to 12% or less.

• It is likely that coffee was not well-dried (to below 13%) since the reported drying times in combination with the high loading rates, make it implausible that this degree of dryness could be reached. This also neglects rain and cool weather during drying, a feature of the early season climate.

• Thickness of coffee cherry layer was found to average 13 cm which far exceeds the recommendation (4 cm). We estimate that the available drying surface is only 1/3 of that required.

• Coffee cherry layer is quite thick making fermentation and mould growth in the coffee mass spontaneous.

e. Storage of coffee • Due to coffee being stored at high moisture over 13% (as above mentioned processing)

conditions for mould growth are high. During a period of observation we see that OTA content may reach to 40 PPb in a lot.

Mouldy cherry drying in a family home plot Typical mixed ripe Robusta cherry on a Vietnamese farm

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WHOLE FRESH CHERRY COFFEE AND MASHED FRESH CHERRY PROCESSING FARMER SURVEY (2004/2005)

11*Bach Than Tuan, Go Nuc Bin, Pham Van Tam et al. ** Tran Kim Loang, Ha Thi Mao et al.

***Anthony Marsh, John M. Frank ***Keith Chapman

Summary The results from the broader farm survey covering 120 farmers in 6 districts in Daklak province conducted in the 2003/04 coffee season showed that the practice of mashing fresh Robusta coffee cherry to accelerate drying was far more wide spread than expected. In some areas up to 30% of farmers were using the practice. There is evidence to suggest that the practice of mashing fresh cherry results in lower quality coffee, due to physical bean damage and a higher incidence of mouldy flavours. A survey was conducted in each of the three districts of Krong Ana, Krong Pak and Dakmil of Daklak and Daknong Province, to compare the differences between coffee processed as dry cherry and mashed cherry from the same farm. Coffee samples of mashed coffee and the whole dry cherry were taken from each farm.

Introduction The TCP/VIE/2903 coffee project was designed to develop methods and techniques for reducing OTA contamination and improving coffee quality throughout the coffee production and processing postharvest management chain. In Viet Nam, farmers have problems with drying of Robusta coffee. One practice farmers have adopted to speed up coffee drying is to mash or crush fresh cherry and then sun-dry the cherry with its damaged skin and mucilage attached. As part of this project a survey of 30 coffee farmers mashing before drying and standard whole cherry drying was conducted in three districts of Daklak and Daknong Provinces to determine the effect of mashing fresh cherry on coffee quality. The survey was conducted during the 2004/2005 coffee season.

Methodology Ten farmers were selected in Krong Ana, Krong Pak and Dakmill districts to supply two samples of coffee each, for evaluation (10 x 3 = 30 farms x 2 = 60 samples). Each farmer processed coffee by mashing the coffee and then drying the mash and by the traditional natural whole cherry drying process producing 30 samples of each process. Farmers dried these coffees on-farm to 12 % moisture. Staff from Cafecontrol, Boun Me Thout coordinated with these farmers throughout the process and collected coffee samples directly from farmers. The field survey began on 5 November and continued to 15 December 2004. The samples were assessed under two different Vietnamese Standards and the following data gathered.

As per Standard 4334-86 “Coffee and its Products - Vocabulary” (Table 1) • Moisture • Foreign matter • Black and broken bean • Mould

11 *CAFECONTROL, Daklak, Buon Me Thuot ** Plant Protection Department - Western Highlands Agro-forestry Scientific and Technical Institute (WASI) *** International Consultants **** Industrial Crops Officer FAO Bangkok Thailand

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As per Standard TCVN 4193-2001 (Tables 2 and 3) • Broken bean • Bean fragment • Black bean • Mouldy bean • Spotted bean • Total defects • Coffee export grade

Survey results and evaluation Moisture content and quality was assessed by quality standards TCVN 4334-86 “Coffee and its Products - Vocabulary”. Table 1 and Figure 1 show that the mashing method has a tendency to produce a higher percentage of black, broken and mouldy beans than whole cherry drying method.

Table 1. Analysis of coffee samples using Viet Nam Standard TCVN 4334-86

District (Average of 10 farms each district) Processing

method Physical standards tested (%)

Krong Ana Krong pak Dakmil Average

Moisture 10.6 10.5 11.4 10.8 Foreign matter 0.58 0.46 0.44 0.49 Black & broken bean 1.48 1.42 1.56 1.49

Whole cherry drying

Mould 0.14 0.10 0.15 0.13 Moisture 10.2 11.0 10.7 10.6 Foreign matter 0.60 0.69 0.50 0.60 Black & broken bean 2.56 2.89 3.01 2.85

Mash cherry then drying

Mould 0.18 0.26 0.18 0.21

Figure 1. Analysis of coffee samples (Table 1)

Foreign matter percentage. The difference between the two processing methods is 0.11%.

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Black and broken bean percentage. The difference between the two methods is 1.36%.

Mouldy bean percentage. The difference between 2 methods is small, 0.08%, because the weather was ideal for coffee drying.

Standard TCVN 4193-2001 provides a method to assess total bean defects for a 300 g sample and then assign a grade to this coffee based on total defects. Six grades are defined for Robusta under this standard — Special Grade: 30 defects, Grade 1: 60 defects, Grade 2: 90 defects, Grade 3: 150 defects, Grade 4: 250 defects, Grade 5: above 250 defects.

Table 2. Export quality assessment of coffee samples using Viet Nam Export Standard TCVN 4193-2001

District (Average of 10 farms each district) Processing method (Total defects/300g)

Krong Ana Krong pak Dakmil Average

Whole cherry drying 130.7 110.2 132.6 124.5

Mash cherry then drying 157.6 165.2 149.1 157.3

Figure 2. Export quality assessment (Table 2)

Total average defects for the whole cherry drying method was 124.5 defects/300g. The highest was Dakmil district at 132.6 and the lowest was Krong Pak district at 110.2. Total average defects for the mashing method was 157.3 defects/300g. The highest was Krong Pak district with165.2 and the lowest was Dakmil district with 149.1. The difference between the two processing methods was 32.8 defects/300g.

Mashing resulted in an average of 26% more defects than drying whole cherry. From a commercial view this resulted in whole cherry samples being rated as Grade 3 coffee while the mashed coffee was rated as Grade 4 coffee.

Table 3 gives a more detailed analysis of individual defects found in the samples of coffee using Standard TCVN 4193-2001. Individual results are weighted to give the total defects shown in Table 2.

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Table 3. Detailed defect analysis of two processing methods using Viet Nam Export Standard TCVN 4193-2001

District Processing method Defects / 300 g Krong Ana Krong Pak Dakmil

Average

Broken bean 26.6 31.4 22.9 27.0 Bean fragment 32.6 34.6 31.9 33.1 Black bean 28.8 29.9 26.7 28.5 Mould bean 4.8 4.2 2.6 3.8

Whole cherry drying

Spotted bean 21.9 23.0 27.5 24.1 Broken bean 49.1 59.3 49.0 52.5 Bean fragment 69.0 68.9 61.9 66.6 Black bean 50.8 43.5 48.0 47.4 Mould bean 5.6 6.3 6.4 6.1

Mashed cherry then drying

Spotted bean 83.1 75.9 75.7 78.2

Figure 3. Table 3 analysis

Broken beans/300g The average number of broken beans per 300g for the whole cherry drying method was 27. The highest is Krong Pak district (31.4) the lowest is Dakmil district (22.9). The average number of broken beans/300g for the mashing method is 52.5. The highest is Krong Pak district (59.3), the lowest is Dakmil district (49.0).

The mashing method gave on average 25.5 or 94% more broken beans than for whole cherry drying.

Bean fragments /300g (with less than ½ of the original bean) The average number of bean fragments/300g for the whole cherry drying method is 33.1. The highest is Krong Pak district (34.6), the lowest is Dakmil district (31.9). The average number of bean fragments/ 300g for the mashing method is 66.6. The highest is Krong Ana district (69.0), the lowest is Dakmil district (61.9).

The mashing method on average gave 33.5 or 124% more fragments than whole cherry drying.

Black beans/300g The average number of black beans/300g for the whole cherry drying method is 28.5. The highest is Krong Pak district (29.9), the lowest is Dakmil district (26.7). The average number of

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black beans/300g for the mashing method is 47.4. The highest is Krong Ana district (50.8), the lowest is Dakmil district (48.0).

The mashing method on average gave 18.9 or 66 % more black beans than whole cherry drying.

Mouldy beans/300g The average number of mouldy beans/300g for the whole cherry drying method is 3.8. The highest is Krong Ana district (4.8 beans), the lowest is Dakmil district (2.6 beans). The average number of mouldy beans/300g for the mashing method is 6.1. The highest is Dakmil district (6.4), the lowest is Krong Ana district (5.6).

The mashing method on average gave 2.3 or 60% more mouldy beans than whole cherry drying.

Spotted beans/300g The average number of spotted beans/300g for the whole cherry drying method is 24.1. The highest is Dakmil district (27.5), the lowest is Krong Ana district (21.9). The average number of spotted beans/300g for the mashing method is 78.2. The highest is Krong Ana district (83.1), the lowest is Dakmil district (21.9).

The mashing method on average gave 54.1 or 224% more spotted beans than whole cherry drying.

Table 4. Cup evaluation of 30 samples (average results from 10 samples from each district)

District Processing method Aroma Flavour Acidity Body Conclusion

Whole cherry drying Characteristic Good Low Good Good Krong Pak Mashed cherry Characteristic Fair Low Fair Fair Whole cherry drying Characteristic Fair Low Fair Fair Krong Ana Mashed cherry Medium Medium Low Medium Medium Whole cherry drying Characteristic Fair Low Fair Fair Dakmil Mashed cherry Medium Medium Low Medium Medium

The standards used for evaluation • Aroma: Aroma of the brewed coffee is evaluated as attractive or not?

Evaluated from: Strong Medium Weak • Flavour: General sensation of taste and smell in the cup of coffee

Evaluated from: Good Fair Medium Weak • Acidity: The cup acidity

Evaluated from: High Medium Low • Body: Physical mouth feel and texture of coffee

Evaluated as follow: Good Fair Medium Weak

Discussion of cup quality evaluation Data in Table 4 show that samples processed from the whole cherry drying method:

• In Krong Ana district, the result of cup-test was good. • In Krong Pak and Dakmil district, the result of cup-tests was fair.

The samples that are processed from the mashing method:

• In Krong Ana district, the result of cup-test was fair. • In Krong Pak and Dakmil district, the result of cup-test was medium.

The cup quality evaluation shows that the difference between the two processing methods was not large. This was because the weather conditions were very warm and sunny during the time

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of the survey. However, in practice, if the weather is not good, such as rain and overcast conditions the quality standard of coffee produced by the mashing method is likely to be much lower than that whole dried cherry with more fermented and mouldy cups.

Discussion of Mycology The results of the mycological analysis do not indicate a strong affect of cherry mashing on the growth of fungi if the data are taken as a whole. With the design of the survey where there are important uncontrolled variables, there is the possibility that in certain combinations these variables could be deterministic.

In Table 5 the occurrence of the mycotoxigenic fungi is characterised. In Krong Pak and Dakmil, it appears that ochre and flavi Aspergilli are favoured by mashing, and A. carbonarius is favoured by cherry drying (number of positive samples). In Krong Ana there were no differences. This could be interpreted as some uncontrolled factors coming together in the former two districts yield a ‘real’ result, or the pattern in only two of three districts implies the result is coincidence.

The mean infection rates are remarkably uniform in the three districts, the maximum infection rates less so. The pattern of this latter parameter is consistent with that of the number of positive samples. The frequency and infection rate of A. carbonarius is far out of line with studies in other countries, and given the technical difficulty in distinguishing this species from other black Aspergilli, this identification must be considered doubtful.

Table 5. Characterisation of the occurrence of mycotoxigenic fungi in dry coffee beans

Krong Ana Kromg Pak Dakmil

A. carb ochre flavi A. carb ochre flavi A. carb ochre flavi CH 4 1 8 8 1 2 9 2 3 Occurrence

(positive sample) M 5 2 8 5 4 7 4 8 8

In both treatments 3 1 5 4 0 1 3 2 2

CH 23 1 3 17 1 5 14 1 3 Mean infection

M 16 1 3 16 2 4 10 5 5

CH 53 1 6 27 1 9 28 1 4 Maximum infection

M 25 1 9 25 3 11 11 9 7 CH = cherry; M = mashed cherry; ‘Occurrence’=number of samples where the fungi was detected; ‘In both treatments’= number of farms where the fungi was detected in both treatments; ‘Mean infection’=the average infection rate of positive samples; ‘Max infection’=maximum observed rate of infection in a district A. niger complex species dominate, and at about the same extent regardless of the samples. Table 6 shows that the infection rate in beans from cherry is similar to that of mashed cherry. Clearly the A. niger complex species are not favoured by one or other of the treatments.

Data from ten farms in each of three districts compared whole cherry drying (CH) with mashed coffee drying (M). A. niger complex species dominated these samples. Data compare the cherry and mashed cherry drying at each farm. In 80% of all samples, the actual infection rates were above 70% (Table 6).

Table 6. Infection rates by members of the Aspergillus niger complex

Infection rates of Niger Aspergilli (cherry and mashed cherry)

Farm Krong Ana Kromg Pak Dakmil 1 -4 40 -37 2 -35 -23 41 3 24 -30 -1

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4 26 16 22 5 43 24 -47 6 -51 56 30 7 -52 -2 -18 8 32 -43 -6 9 -73 -8 43 10 12 1 -9

Conclusions Two different processed samples from each of 30 farms were evaluated using standards TCVN 4193-2001 and TCVN 4334-86. The data showed the quality of coffee produced by the whole cherry drying method is overall slightly better than the quality of coffee produced by the mashing method. The results of the mycological analysis do not indicate a strong affect of cherry mashing on the growth of fungi compared to normal drying of whole cherry. Even so, defect levels for this survey are higher in mashed coffee (26% more defects) than in whole dried cherry. From a commercial viewpoint, this resulted in whole cherry samples being rated as Grade 3 coffee while the mashed coffee was rated as Grade 4 coffee. Weather conditions were very warm and sunny during the survey and ideal for drying coffee. If conditions had been otherwise (rainy and overcast), the quality of coffee produced by the mashing method would be much lower than that whole dried cherry.

Recommendations Mashing of coffee is not recommended. Mashing downgrades coffee quality and in wet conditions, and we know from other trials it produces mouldy, off-flavoured, fermented coffee of an unacceptable standard.

Acknowledgements We sincerely acknowledge the cooperation of the farmers surveyed in Krong Pak, Krong Ana and Dakmil districts and thank FAO for the funding support to undertake the survey.