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EFFECT OF ALGINATE-BASED EDIBLE COATING AND HONEY

TREATMENTS ON KEEPING QUALITY OF FRESH-CUT STAR FRUIT

(Averrhoa carambola L.)

NOOR HIDAYAH BINTI MOHD NAWI

Final Year Project Report Submitted in

Partial Fulfilment of the Requirements for the

Degree of Bachelor of Science (Hons.) Food Science and

Technology in the Faculty of Applied Sciences

Universiti Teknologi MARA

JANUARY 2012

2

This Final Year Project Report entitled “Effect of Alginate-Based Edible

Coating and Honey Treatment on the Keeping Quality of Fresh-Cut Star

Fruit (Averrhoa Carambola L.)” was submitted by Noor Hidayah binti Mohd

Nawi, in partial fulfilment of the requirements for the Degree of Bachelor of

Science (Hons.) Food Science and Technology, in the Faculty of Applied Sciences

and was approved by

_________________________________

Madam. Fuziah Mohamed Othman

Supervisor

B. Sc. (Hons.) Food Science and Technology

Faculty of Applied Sciences

Universiti Teknologi MARA

40450 Shah Alam

Selangor

___________________________ ____________________________

Dr. Anida Yusoff Assoc. Prof. Dr. Noorlaila Ahmad

Project Coordinator Head of Programme

B. Sc. (Hons.) Food Science and B. Sc. (Hons.) Food Science and

Technology Technology

Faculty of Applied Sciences Faculty of Applied Sciences

Universiti Teknologi MARA Universiti Teknologi MARA

40450 Shah 40450 Shah Alam

Selangor Selangor

Date:_____________________

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ACKNOWLEDGEMENT

Assalamualaikum w.b.t

In the name of Allah The Most Gracious and The Most Merciful. Alhamdulillah all

praises to Allah for the strengths and His blessing I managed to finish the final

year project report and fulfilled the entire requirement in a given time. It is

undeniable that it quite difficult for me to start writing the proposal and project

report at the beginning but I managed to finish it up successfully. Upon completion

of this project, I would like to express my little appreciation to many parties that

directly or indirectly involved in making this into view.

Special appreciation goes to my beloved supervisor, Mrs. Fuziah Mohamed

Othman for her supervision, giving me guideline, assistance and constant support

in fulfilling this report writing. Her invaluable help of constructive comments,

suggestions and recommendations has given me strength to be more comparative

and creative in solving problems, thus mentally prepared to face more challenging

in the future. Not forgotten, my heartfelt thanks goes to Assoc. Prof. Dr. Noorlaila

Ahmad, the head of programme of Bachelor in Sc. (Hons.) Food Science and

Technology, for her kindness in making me deeply understands and evaluates a

better way to propose a project.

I would like to express a warm gratitude and appreciation to the Pasir Puteh

MARDI station and their staff, Mr. Mohd Azhar for his cooperation and

permission to supply the star fruit samples. Besides, my special thanks to all staffs

of Food Technology especially Mrs. Siti Marhani, Miss Hariyah Hashim, Mrs.

Norahiza, Miss Nurul Shuhada, Mr. Osman and Mr. Mohd Fadzli for their

technical supports and valuable advice.

My deepest gratitude goes to my beloved family for their endless love, prayers,

moral support and encouragement. Last but not least, sincere thanks to all my

friends for their kindness and support in completion this report. Thanks for the

friendship and memories. Besides, my gratitude also goes to those who indirectly

contributed in this report writing and in expressing their opinion and

recommendations with the greatest wishing thank you very much.

Noor Hidayah binti Mohd Nawi

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TABLE OF CONTENTS

Page

ACKNOWLEDGEMENT iii

TABLE OF CONTENTS iv

LIST OF TABLES vi

LIST OF FIGURES vii

LIST OF ABBREVIATIONS viii

ABSTRACT x

ABSTRAK xi

CHAPTER 1 INTRODUCTION

1.1 Background and problem statement 1

1.2 Significance of study 3

1.3 Objectives of study 4

CHAPTER 2 LITERATURE REVIEW

2.1 Background of star fruit 5

2.1.1 Varieties of star fruit 6

2.1.2 Nutritional value of star fruit 6

2.2 Harvesting 8

2.2.1 Selection and storage of star fruit 8

2.2.2 Postharvest of star fruit 9

2.2.3 Physiological and physical disorders 9

2.3 Maturity of star fruit 10

2.4 Grading standard 12

2.5 Techniques used to improve the shelf-life and fruits quality 14

2.5.1 Film wrappings 15

2.5.2 Modified atmosphere packaging (MAP) 15

2.5.3 Controlled atmosphere packaging (CAP) 16

2.6 Edible Coatings 17

2.7 Types of edible coatings and films 17

2.6.1 Polysaccharide – based coatings 18

2.6.2 Lipid – based coatings 19

2.6.3 Protein – based coatings 19

2.8 Advantages of edible coatings and films 20

2.9 Disadvantages of edible coatings and films 20

2.10 Honey 20

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2.11 Alginate 21

2.12 Calcium and ascorbate 22

CHAPTER 3 METHODOLOGY

3.1 Materials 23

3.1.1 Star fruits 23

3.1.2 Edible coating materials 23

3.1.3 Film-forming and dipping treatment solutions 24

3.2 Methods 25

3.2.1 Pre-treatment of samples 26

3.2.2 Application of coating 27

3.2.3 Visual appearance 27

3.2.4 Weight loss determination 27

3.2.5 Firmness evaluation 28

3.2.6 Surface colour development 28

3.2.7 pH measurement 28

3.2.8 Total soluble solid (TSS) determination 28

3.2.9 Oxygen and carbon dioxide concentration 29

3.2.10 Statistical analysis 29

CHAPTER 4 RESULTS AND DISCUSSION

4.1 Visual appearance 30

4.2 Effect on weight loss 32

4.3 Effect on firmness 34

4.4 Effect on colour 35

4.5 Effect on pH 38

4.6 Effect on total soluble solid 39

4.7 Oxygen and carbon dioxide concentration 40

CHAPTER 5 CONCLUSION AND RECOMMENDATIONS 43

CITED REFERENCES 44

APPENDICES 51

CURRICULUM VITAE 87

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LIST OF TABLES

Table Caption Page

2.1 Nutritional information of star fruits 7

2.2 Grading standards of ordinary star fruits based

on quantitative and qualitative evaluation

13

3.1

Coatings and dipping sample formulations 25

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LIST OF FIGURES

Figure Caption Page

2.1 Star fruit Maturity Index 11

3.1 Overall experimental scheme of study 26

4.1 Visual appearance of fresh-cut star

fruits during storage at 5°C for 12 days

30

4.2.1 Percentage weight losses of fresh-cut

star fruits during storage at 5°C

33

4.3.1 Firmness of fresh-cut star fruits during

storage at 5°C

34

4.4.1 Lightness (L* values) of fresh-cut star

fruits during storage at 5°C

35

4.4.2 Greenness (a* values) of fresh-cut star

fruits during storage at 5°C

36

4.4.3 Yellowness (b* values) of fresh-cut

star fruits during storage at 5°C

36

4.5.1 pH measurement of fresh-cut star

fruits during storage at 5°C

38

4.6.1 Total soluble solid (TSS) of fresh-cut

star fruits during storage at 5°C

39

4.7.1 Oxygen concentration of fresh-cut star

fruits during storage at 5°C

40

4.7.2 Carbon Dioxide concentration of

fresh-cut star fruits during storage at

5°C

41

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LIST OF ABBREVIATIONS

% : Percent

°C : Degree Celsius

°F : Degree Fahrenheit

AA : Ascorbic Acid

ANOVA : Analysis of variance

Ca2+

: Calcium ion

CaCl2 : Calcium Chloride

CAP : Controlled Atmosphere Packaging

cm : Centimetre

DNMRT : Duncan‟s new multiple range test

F1, 2, 3, 4 : Formulation 1,2,3,4

CO2 : Carbon Dioxide

FAMA : Federal Agricultural Marketing Authority

FDA : Food and Drugs Administration

GRAS : Generally Recognised As Safe

g : Gram

kg : Kilogram

M : Molar

m : Meter

MAP : Modified Atmosphere Packaging

MARDI : Malaysian Agricultural Research and Development

Institute

mg : Milligram

mL : Millilitre

mm : Millimetre

N : Newton

NaOH : Sodium Hydroxide

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O2 : Oxygen

PPO : Polyphenol Oxidase

PMA‟s : Pre-Market Approval

PVC : Polyvinyl chloride

TSS : Total Soluble Solid

w/v : Weight by Volume

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ABSTRACT

EFFECT OF ALGINATE-BASED EDIBLE COATING AND HONEY

TREATMENTS ON KEEPING QUALITY OF FRESH-CUT STAR FRUIT

(Averrhoa carambola L.)

The effect of alginate-based edible coating with honey treatments on keeping

quality of fresh-cut star fruit (averrhoa carambola L.) was investigated. Fresh cut

star fruits with maturity index 3 were coated with alginate film forming solution

prepared from 2% w/v powdered alginate, 1% w/v glycerol with 0.13% w/v

sunflower oil and water. After the excess of coating drip off for a minute,

subsequently immersed with one of four different dipping solution formulations:

2% calcium chloride (CaCl2) with 2% ascorbic acid (AA) (F1), 2% calcium

chloride (CaCl2), 2% ascorbic acid (AA) with 5% honey (F2), 2% calcium chloride

(CaCl2), 2% ascorbic acid (AA) with 10% honey (F3) and 2% calcium chloride

(CaCl2), 2% ascorbic acid (AA) with 15% honey (F4). The effectiveness of these

treatments were assessed by evaluating their impact on the visual appearance,

weight loss, firmness, oxygen and carbon dioxide concentration, total soluble

solid, pH, and colour measurement. Overall, it was found that alginate-based

coating with honey treatment prolonged the shelf life and keeping quality of fresh

cut star fruit up to 12 days of storage at 5°C. It was demonstrated that the

application of all treatments were able to slow down ripening process and

maintaining the keeping quality of fresh cut star fruit in term of texture (firmness),

giving better appearance and aroma, reducing percentage weight loss and acting as

good gas and moisture barrier depending on the formulation. It also lowering the

changes in pH and maintaining desirable pH of fresh cut star fruit. Moreover, it

was able to retard and slow down the enzymatic browning on fresh cut star fruit.

Coating and dipping treatment with F4, containing 15% honey solution, was the

most suitable and effective coating for fresh cut star fruit except for visual colour.

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ABSTRAK

KESAN KAEDAH SALUTAN BERASASKAN ALGINAT DAN KAEDAH

CELUPAN MADU PADA KUALITI PENYIMPANAN POTONGAN

BELIMBING SEGAR (Averrhoa carambola L.)

Kesan kaedah salutan berasaskan alginat dan kaedah celupan madu pada kualiti

penyimpanan potongan belimbing segar telah di kaji. Potongan belimbing segar dengan

indeks kematangan 3 telah disalut dengan larutan lapisan berasaskan alginat yang terdiri

daripada 2% berat/isipadu serbuk alginat, 1% berat/isipadu gliserol dengan 0.13%

berat/isipadu minyak bunga matahari dan air. Selepas lapisan salutan di biar menitis satu

minit, kemudian ia di celup dalam salah satu daripada empat rumusan celupan berbeza:

2% kalsium klorida dengan 2% askorbik asid (F1), 2% kalsium klorida, 2% askorbik asid

dengan 5% madu (F2), 2% kalsium klorida, 2% askorbik asid dengan 10% madu (F3), 2%

kalsium klorida, 2% askorbik asid dengan 15% madu (F4). Keberkesanan rawatan ini telah

di nilai berdasarkan kesan penerimaan keseluruhan, penurunan berat asal belimbing,

kekerasan, kepekatan oksigen dan karbon dioksida, jumlah gula larut, keasidan dan

perubahan warna. Secara keseluruhan didapati bahawa kaedah salutan berasaskan alginat

dan rawatan dengan madu dapat memanjangkan tempoh penyimpanan dan kualiti

potongan segar belimbing sehingga 12 hari pada suhu 5°C. Ia menunjukkan kaedah

rawatan dengan semua rumusan mampu memperlahankan proses masak, dan mengekalkan

kualiti potongan segar belimbing dari segi kekerasan, memberi rupa dan aroma yang lebih

baik, mengurangkan peratusan pengurangan berat dan bertindak dalam mengurangkan

kadar respirasi dan kehilangan kelembapan yang bergantung kepada rumusan berbeza. Ia

juga bertindak dalam mengurangkan perubahan keasidan dan mengekalkan kadar keasidan

pada paras rendah potongan buah belimbing. Selain itu, ia boleh menghalang dan

memperlahankan perubahan warna disebabkan oleh enzim. Di dapati, rumusan salutan dan

celupan dengan 15% madu (F4) adalah yang paling sesuai dan berkesan sebagai penyalut

potongan buah belimbing segar untuk semua parameter kecuali bagi parameter warna

fizikal.

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CHAPTER 1

INTRODUCTION

1.1 Background and problem statement

Nowadays, people are particularly very conscious of their health. They are

concerned of the types of foods that they consumed everyday whether it is healthy

or not. Several epidemiological studies have been done and the results have

indicated that a high intake of plant products is associated with a reduced risk of a

number of chronic diseases such as atherosclerosis and cancer (Gungaard et al.,

2003; Hashimoto et al., 2002).

The fresh-cut fruits industries has potential to grow due to their characteristics of

freshness, low caloric contents, commodity to be used and an active promotion of

fruits and vegetables as basic components of a healthy diet (Rosa et al., 2008).

However, because of health benefits claiming by taking the natural products, it has

been responsible for the current increasing of product and consumption of fresh-

cut fruits.

Eating quality of fresh-cut fruit products is not only influenced by the stage of

ripeness at cutting (Gorny et al., 1998) but also is highly dependent on the post

harvest history of fruit before processing. The quality of fresh-cut fruits is usually

judge based on their appearance and freshness. However, a mechanical operation

during processing damage the fruit tissues which is turn limits the shelf-life of the

products. This alters the integrity of fruits bringing about negative effects on

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product quality such as browning, off-flavour development, texture breakdown and

the presence of micro-organisms on the fruit surface may compromise the safety of

fresh-cut fruits (Rojas-Grau et al., 2009).

Coatings of edible material applied as a thin layer to enhance the quality and

extend the shelf life of fresh-cut fruits can act as a barrier in reducing both

respiration and water loss (Kester and Fennema, 1986; Krochta et al., 1991;

Guilbert et al., 1996). It is applied on cut apples to produce a modified atmosphere,

which reduces decay, delays ripening and colour changes, improves appearance

and functions as a carrier of anti-microbial, anti-browning agents, texture

enhancers, nutraceuticals, flavours and volatile precursors (Olivas and Barbosa,

2005).

Polysaccharide-based coatings have been used to extend the shelf-life of fruits and

vegetables by reducing respiration and gas exchange due to selective permeability

to O2 and CO2 (Nussinovitch, 2000). Alginate is biopolymer that could be

considered for edible film and coating because of their unique colloidal properties

and their ability to form strong gel or insoluble polymer upon reaction with

multivalent metal cations like calcium (King, 1983 and Rhim, 2004).

Alginate is a polysaccharide isolated from marine brown algae (Phaeophyceae) is

finding increasing use in the food industry as texturizing and gelling agents

(Mancini and McHugh, 2000; Yang and Paulson, 2000; Lu and Ye, 2009).

Alginate is a salt of alginic acid, a polymer of D-mannuronic acid and L-guluronic

acid. Alginate has unique colloidal properties and can form strong gels or insoluble

polymers through crossed linking with Ca2+

by post-treatment of CaCl2 solution.

Such biopolymer-based films can keep good quality and prolong shelf life of foods

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by increasing water barrier, preventing microbe contamination, maintaining the

flavour and texture of the fresh-cut fruits.

Many studies have been conducted in order to understand the postharvest factors

that influence star fruit quality. However, information is limited on the preharvest

and mechanical processing aspects that influence fruit physiology especially for

fresh-cut fruit. Fresh-cut fruit products, including star fruit (Averrhoa carambola

L.), have limited marketability due to cut surface browning attributed to phenolic

compound oxidation by enzymes, such as polyphenol oxidase (PPO). Carambola

(Averrhoa carambola L.) is a fruit with great possibilities as a fresh-cut product.

Carambola slices have great potential for use in salads and as garnishes for drinks

or cocktails (Oslund and Davenport, 1983).

According to Watada et al., (1996) the use of film wraps or edible coatings can

modify the internal atmosphere, which had been shown to be beneficial in

extending shelf life. However, extensive modification of the atmosphere can cause

injury to tissue, thus further study is need to determine the recommended

atmosphere.

1.2 Significance of study

The use of polysaccharide-based coating (alginate) and honey treatment in this

study is to form a safe and edible coating film for fresh-cut star fruits. The fresh-

cut star fruits have been chosen because it is well known that easily to deteriorate

due to several factors like mechanical processing, improper handling and present

of oxidative browning enzymes and others. Significantly, the use of coating and

dipping treatment is to minimize the lost of nutrient by minimal processed. The

fruits also are widely recognised for their contribution to human nutrition and

health benefits. Besides, the results of this study will be useful in order to give

information about the formulation of edible coating and dipping treatments for

fresh-cut fruit as compared to the fresh-cut fruit without treatments.

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1.3 Objectives of study

The main intentions of this study are:

1. To compare the effectiveness of edible coating treatment and dipping in

maintaining keeping quality of fresh-cut star fruit.

2. To determine the effect of Alginate-based coating and honey dips treatment on

the changes of keeping quality attributes of fresh-cut star fruits up to 12 days of

storage at 5°C.

3. To identify the most suitable formulation for Alginate-based coating and honey

dips treatment for fresh-cut star fruits.

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CHAPTER 2

LITERATURE REVIEW

2.1 Background of star fruit

Star fruit or its scientific name Averrhoa carambola L. is classified in the division

Magnoliophyta, class Magnoliopsida, order Geraniales, family Oxalidaceae (The

Columbia Encyclopaedia, Sixth Edition, 2008). It believed to originate in Sri

Lanka, the Moluccas, India and Indonesia then it has been cultivated in Southeast

Asia and Malaysia for many centuries but now it cultivated in the United States.

Averrhoa carambola is a small, evergreen, multi-stemmed tree 3 to 5m high or

rarely 10m high, attaining 15cm diameter at the base; bark light brown, smooth or

finely fissured. Leaves alternate, pinnate, 15 to 25cm long, disposed more or less

in a horizontal plane, shortly petiolate with 7 to 9 pendant leaflets; leaves have the

peculiarity of being sensitive to touch in the same way as certain Mimosa species.

Inflorescence in panicles 2 to 5cm long in the axils of old leaves; flowers

pentamerous, with a calyx of 5 pink sepals surrounding the purple corolla;

androecium contains 5 fertile stamens and 5 staminoids; gynoecium bears 5

slender united styles. Fruit a large, indehiscent berry, 5 to 8cm long; with a

characteristic shape in cross-section resembling a 5-pointed star; yellowish-green,

becoming orange-yellow when ripe. Each cell of the fruit contains five arillate

seeds (Campbell, 1989).

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In Malaysia it closely relative called “belimbing”. Other names include carambola,

Chinese star fruit, star apple and quite appropriately, five-angled fruit. This scented

fruit named after a twelfth century Arabic physician and philosopher, Averrhoes.

The fruit, with its sweet-sour taste is a popular delicacy here, most often eaten raw.

The fruit displays an attractive star-shape when cut, thus its popular name. It has a

waxy, golden yellow to green colour skin with a complicated flavour combination

that includes plums, pineapples, and lemons (Nakasone and Paull, 1998).

2.1.1 Varieties of star fruit

According to Nakasone and Paull (1998) there are two types of star fruit are

grown, tart and sweet. Tart varieties typically have narrowly spaced ribs, while

sweet varieties tend to have thick, fleshy ribs. The tastes between the two are

hardly distinguishable, as the tart variety still has some sweetness. There are

several cultivars of star fruits introduced in the markets.

There are two main types distinguished by bearing either sour or sweet fruits. The

sweet types contain up to 5% sugars and sour types have as much as 1% acid. A

Chinese type, “Fuang Tung” is very sweet, while “Brazilian” ones are full of

vitamin C. Exotic types of star fruit from Hawaii called “Golden Star”, Taiwan

called with “Tean Ma” and “Min Tao” and the famous star fruits cultivar from

Columbia is “Icambola” (Faciolla, 1990).

2.1.2 Nutritional value of star fruit

Star fruits are an excellent source of vitamin C, naturally sodium and cholesterol

free. A small whole star fruit will provide approximately 2/3 cup sliced. Star fruit

is very low in saturated fat, cholesterol and sodium. It is also a good source of

pantothenic acid and potassium, and a great source of dietary fibres, vitamin C and

copper. One medium size of star fruit contains about 40 calories. Consuming about

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five daily servings of fruits lowers the chances of cancer. A recent study found that

eating nine or ten servings of fruits and vegetables combined with three servings of

low fat dairy products are very effective in lowering blood pressure (Hung et al.,

2004).

Table 2.1 Nutritional information of star fruits

Serving size: 1 cup (132g), cubed

Amount per serving

Calories 41 kcal Calories from Fat 4 kcal

% Daily Value*

Total Fat 0g 1%

Cholesterol 0mg 0%

Sodium 3mg 0%

Total Carbohydrate 9g 3%

Dietary Fibres 4g 15%

Sugars 5g

Protein 1g

Vitamin A 2% Vitamin C 76%

Calcium 0% Iron 1%

*Percent Daily Values are based on a 2000-calorie diet. Your daily values may be higher or low

depending on your calorie needs.

Source: PMA‟s Labelling Facts (2008).

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2.2 Harvesting

Seedlings of star fruits take about four to five years to produce fruit. Star fruit tree

flowers three to four times a year follow by crops, the fruiting is especially heavy

over summer, other peak seasons are November to December, and March to April,

continuous harvesting is possible year-round in tropical regions. The best to know

for ripeness is to eat one to taste how sweet the fruit is. The average of 300 pounds

of fruit can be harvesting from a healthy grown tree per year (Anon, 1996).

2.2.1 Selection and storage of star fruit

Fruits are hand harvested carefully to avoid scratching the skin that might affect

the quality of the star fruits. High quality star fruit will give firm, shiny skinned

even colour fruit. Star fruit suffers from fruit fly maggots, particularly Dacus

dorsalis (Southeast Asia), and fruit-piercing moth (Othreis spp., Australia);

bagging prevents infestation but post harvest rots are more serious: the slightest

blemish invites infection by Ceratocystis, Colletotrichum, and Dothoriella and

Phomopsis fungi (Watson et al., 1987).

However, star fruits will ripen at room temperature and have lightly brown edges

on the ribs when it is ripe. Unripe star fruit should be turn often, until they are

yellow in colour and ripe with light brown ribs. Star fruit can be stored at room

temperature for two to three days or unwashed, and refrigerated, in a plastic bag

for up to one week. The storage length of star fruit varies with ripeness when

placed in chiller. Lower relative humidity (RH) of the storage may result in more

severe rib edge browning if the star fruit held at 20°C (68°F). However, the star

fruits are extremely perishable where it shelf life at room temperature ranges from

three to four days depending on the storage atmosphere (Kader, 1999).

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2.2.2 Post harvest of star fruit

Star fruit (Averrhoa carambola L.) is commercially harvested at colour-break to

reduce susceptibility to mechanical injury during handling. Sugar levels remain

constant during storage, although star fruits will continue to lose chlorophyll and

develop carotenoids after harvest. Acidity can decline during storage, and this is

often undesirable as it can be associated with blandness (O'Hare, 1993). The

carambola has the characteristics of a non-climacteric fruit. Increases in carbon

dioxide and ethylene production rates occur after the fruit is consider ripe and

these tend to be relating to microbial decay or tissue senescence.

A storage temperature of 5°C is capable of maintaining fruit with a minimum of

physiological changes for at least 6 weeks, provided moisture loss is controlled.

Storage life is largely limited by disease, which commonly develops from lesions

either present at harvest like insect damage or occurring during product handling

(O'Hare, 1993).

2.2.3 Physiological and physical disorders

The previous study by Kader (1999), shows chilling injury can be determine by

some observation. The symptoms include surface pitting where the pits are either

small (<1mm), deep and dark brown or large (1-2mm), superficial, and light

brown, and rib-edge browning. These symptoms have been reported in some

carambola cultivars after two weeks at 0°C (32°F) or six weeks at 5°C (41°F)

followed by two days at 20°C (68°F).

Other than that, the physical damage also may occur by post-harvested fruit where

the rib-edge browning and stem-end browning can result from surface abrasions

and other types of bruising. The browning intensity increases with water loss from

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the fruits. Handling star fruits with care to minimize bruising is essential to

reducing post harvest losses (Watson et al., 1987).

Other types of defects that might be occurring are shrivelling and heat

damage. Symptoms for shrivelling is the star fruit become visible when it lose

about 5% or greater of their weight due to water stress. However, symptoms of

heat damage shows the skin browning and flesh softening may occur when star

fruit are expose to heat treatments such as 46°C (115°F) for 35 to 55 minutes for

insect control to satisfy quarantine requirements. Better alternatives may be cold

treatment and/or irradiation.

Post harvest diseases of star fruit may be caused by Altenraria

alternata (especially on chilled fruits), Cladosporium cladosporioides, or

Botryodiplodia theobromae. These usually occur at physically damaged sites on

the fruits during prolonged storage. Minimizing physical damage throughout the

harvesting and post harvest handling operations and prompt cooling to 5°C (41°F)

can greatly reduce incidence and severity of post harvest diseases on star fruit

(O'Hare, 1993).

2.3 Maturity of star fruit

Maturation is the stage of development leading to attainment of physiological and

horticultural maturity. Maturity at harvest is the most important factor that

determines the storage life and quality of star fruit. Immature fruits are more

subject to mechanical damage and are of inferior flavour quality when it ripe.

However, overripe fruits are likely to become soft and mealy with insipid flavour

soon after harvest (Kader, 1992).

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Normally, colour is use as an index to determine the maturity of the fruits. Star

fruit maturity are based on the colour changes from green to yellow which is

accompanied by an increase in soluble solids including sugars for it sweetness.

Star fruit should be picking when fully yellow to assure good eating quality. The

colour break (1/2 to 3/4 of fruit is yellow) is used as the commercial maturity index

because these fruits are firmer and easier to handle (Kader, 1999). Some indexes

have been proposing to determine the maturity of the star fruits.

Index 1: Dark Green.

Not suitable for

harvest.

Index 2: Green

overall with stripes of

yellow. Suitable for

export by sea.

Index 3: Green

overall with yellow.

Suitable for export by

sea.

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Figure 2.1 Star fruit Maturity Index

Source: Federal Agricultural Marketing Authority (FAMA), (2010).

2.4 Grading standard

The Malaysia Federal Agriculture and Marketing Authority, (FAMA) established

three grades for golden yellow star fruit belonging to Averrhoa carambola L.

genus. The grades are FAMA no.1, FAMA no. 2 and FAMA no. 3 are determined

Index 4: Yellow

green. Suitable for

export by air.

Index 5: Yellow

overall with little

green. Suitable for

local consumption.

Index 6: Yellow to

orange overall. Ripe

fruit. Suitable for

local consumption.

Index 7: Dark yellow

to orange overall.

Ripe fruit. Suitable

for local

consumption with

limited storage life.

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by qualitative and quantitative criteria stated by FAMA. The star fruit should be

around 635–15cm long and approximately 9cm wide. It should have 4 to 6 pointed

stars that run from top to bottom. However, its colour should be translucent green

or orange-yellow with minimum darkening or other discoloration defects. The top

grade star fruits are allowed little variation in these quality characteristics, while

the lower grade is allowed greater variation and degradation.

Generally, star fruits of the same variety do not show significant variation in sizes

and weights (Abdullah et al., 2006). This is the FAMA grading standards as

summarised in Table 2.2 below. Following FAMA standards, the fruit‟s colour

was used to estimate the degree of ripeness while the fruit‟s shape was used to

determine the overall quality feature.

Table 2.2 Grading standards of ordinary star fruits based on quantitative and

qualitative evaluation

Grade Quantitative/Qualitative Features Tolerances (%)

FAMA

no. 1

- Uniform in colour

- Freshness (flesh firmness or texture)

- Damage due to mechanical injuries,

bruises, diseases, damage by insects

affecting more than 25% of fruit surface

- Defect (abnormal shape including

discolouration affecting 10% to 25% of

fruit surface

- Uniform in size (weight >200g)

5

5

5

5

5

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