DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY

COLLEGE OF AGRICULTURE, JNKVV, JABALPUR

Prepared By: Dr. Priti Jain and Er. K. C. Mahajan

Course Title: Post Harvest Management and Value Addition of Fruits and Vegetables

Credit: 2 (1+1)

B.Sc.(Ag.). Third Year, Second Semester

1. LECTURE NOTES

Importance of Fruits and Vegetables Crops

Horticulture crops perform a vital role in the Indian economy by generating employment,providing raw material to various food processing industries, and higher farm profitability due tohigher production and export earnings from foreign exchange.

a) Horticulture crops are a source of variability in farm produce and diets.b) They are a source of nutrients, vitamins, minerals, flavour, aroma, dietary fibres, etc.c) They contain health benefiting compounds and medicines.d) These crops have aesthetic value and protect the environment.e) The comparative production per unit area of horticultural crops is higher than field crops,

e.g., paddy crop gives a maximum yield of only 30 q/ha, while banana crop gives 300–450 q/ha and grapes 90–150 q/ha.

f) Fruit and plantation crops can be cultivated in places where the slope of land is uneven orundulating. Mango and cashew nut are cultivated on a large scale in hilly and hill backarea of the Konkan region.

g) The crops are useful for cultivation in wasteland or poor quality soil.h) Such crops are of high value, labour intensive and generate employment throughout the

year.i) Horticultural produce serves as raw material for various industries, such as processing,

pharmaceutical, perfumery and cosmetics, chemical, confectionery, oils and paints, etc.j) They have national and international demand and are a good source of foreign exchange.

Table 1: Difference between fruits and vegetables

S.No.

Fruits Vegetables

1. Most fruit plants are perennials. Most vegetables are annuals.2. Fruit plants are generally woody in nature. Vegetable plants are,

generally, herbaceous andsucculents.

3. They are commercially propagated asexually. They are commerciallypropagated sexually (by seed).

4. Fruit plants require special cultural practices, i.e.,training, pruning, etc.

Vegetables are seasonal andonly staking and pruning arerequired in some crops.

5. Fruits are mostly consumed fresh after ripening. Most vegetables requirecooking for consumption.

Classification of vegetable crops

If the growing of each vegetable is dealt with in detail, it will lead to too much repetition. It is,therefore, desirable to classify vegetable crops into certain groups as per their similarities (Fig.1). This will also help in studying them easily.

Based on the nature of plant (stem)

(a) Herbaceous and succulents: Leafy vegetables(b) Shrubs: Brinjal, chilli, tomato, etc.(c) Trees: Drumstick, jackfruit, etc.(d) Vines: Cucurbits, etc.

Based on the life span (from seed-to-seed)

(a) Annuals: The life span of annual plants or annuals is a season or a year, e.g., brinjal,chilli, cabbage, cauliflower, cucurbits, tomato, leafy vegetables, etc.

(b) Biennials: The life span of biennials is of two seasons or two years, e.g. onion,radish, carrot, etc.

(c) Perennials: The life span of perennial plants is more than two years, e.g., drumstick(moringa), asparagus (shatawari), pointed gourd (parwal), etc.

Fig. 1: Classification of vegetable crops

Based on the method of commercial propagation

(a) Sexually propagated (by seed): Brinjal, chilli, cauliflower, cabbage, cucurbits, tomato,leafy vegetables, etc.

(b) Asexually propagated (vegetative parts): Asparagus, dioscorea, potato, sweet potato,onion, garlic, taro, yam, etc.• Cuttings: Asparagus• Bulbs: Onion, garlic• Rhizomes: Colocasia, ginger, coleus• Tubers: Potato, sweet potato

Based on the method of planting

(a) Directly sown plants: Okra, leafy vegetables, carrot, radish, peas and beans(b)Transplanting: Tomato, brinjal, chilli, cauliflower, cabbage, onion, potato, sweet

potato, cassava, pointed gourd, etc.(c) Crops grown from underground parts

• Root vegetables: Radish, carrot, turnip, beetroot• Rhizome: Colocasia, ginger• Bulb: Onion, garlic• Tuber: Potato, sweet potato, cassava and yam

Based on intercultural practices

(a) Solanaceous crops: Tomato, brinjal, chilli, bell pepper, potato(b) Cole crops: Cabbage, cauliflower, knol-khol, broccoli and Brussels sprouts(c) Leafy vegetables: Spinach, methi, lettuce and chaulai (amaranthus)(d) Pods or capsules: Pea, cowpea, cluster bean, okra

(e) Cucurbits: Gourds, melons, cucumber, pumpkin(f) Root crops: Carrot, radish, turnip, beetroot

Based on climatic requirements

(a) Temperate vegetables: Radish, potato, carrot, cabbage, cauliflower, knol-khol,broccoli, etc.

(b) Tropical and subtropical vegetables: Watermelon, musk melon, cucumber, tomato,brinjal, chilli, etc.

Based on the season of growth

In India, seasonal or annual vegetables can be classified according to their season ofgrowth. Season of growth is the period in which the climatic conditions are favourablefor the growth and production of a crop.

(a) Kharif season vegetables: These may also be called rainy season crops. Thesevegetables require hot and humid climate. The season tentatively starts from 7 Juneand lasts till 6 October every year. The sowing of seeds may be undertaken frommid-May to late July. Vegetables, like okra, cowpeas, cluster beans, etc., areexamples of Kharif vegetables.

(b) Rabi or cool season vegetables: These may also be called cool or winter season cropsas these vegetables require low temperature for growth. The season tentatively startsfrom 7 October and lasts till 6 February. The sowing of seeds may be undertakenfrom mid-September to late October. Vegetables, like peas, radish, carrot,cauliflower, cabbage, knol-khol, leafy vegetables, etc., are examples of Rabivegetables.

(c) Summer or warm season vegetables: The season tentatively starts from 7 Februaryand lasts till 6 June. The sowing of seeds may be undertaken from mid-January tolate February. These crops require hot and dry climatic conditions for better growthand maximum production. Cluster bean, musk melon, cucumber, watermelon, etc.,are summer season vegetables.

Based on plant part used as vegetable

(a) Stem and leaves: Cabbage, lettuce, spinach, methi, coriander, amaranthus, etc.(b) Flowers: Broccoli (head ‘flower buds’), cauliflower (curd ‘pre-floral stage’), etc.(c) Fruits: There are various stages where the fruits of vegetable crops can be harvested

for consumption, such as• Ripened fruits: Watermelon, musk melon, tomato, etc.• Immature and tender fruits: Cucumber, bottle gourd, bitter gourd, ridge gourd,

okra, brinjal, green chilli, cowpea, French beans, dolichos beans, etc.(d) Seeds: Peas, etc.(e) Underground parts of plant

• Taproot: Tapering root growing vertically downward, e.g., carrot, radish, etc.• Bulb: A fleshy leaved storage organ in some vegetables sending adventitious

roots downward and leaves upward, e.g., onion, garlic, etc.• Tuber: Thick, short and rounded underground stem with modified nodes and buds,

e.g., potato, sweet potato, etc.• Rhizome: Underground root-like stem having roots and shoots, e.g., colocasia,

ginger, etc.

Nature and Causes of Post-Harvest Losses

Losses occur after harvesting is known as post harvest losses. It starts first from the field, afterharvest, in grading and packing areas, in storage, during transportation and in the wholesale andretail markets. Several losses occur because of poor facilities, lack of know-how, poormanagement, market dysfunction or simply the carelessness of farmers.

(a) Extend of post-harvest loss: It is evident that the estimation of post-harvest loss is essentialto make available more food from the existing level of production.A recent joint study conducted by the management consultancy firm, McKinsey and Co. and(The Confederation of Indian Industry (CII), at least 50% of the production of fruits andvegetables in the country is lost due to wastage and value destruction. The wastage cost isestimated to be Rs.23, 000 crores each year. Swaminathan Committee (1980) reported thepost-harvest handling accounts for 20-30% of the losses at different stages of storage,grading, packing, transport and finally marketing as a fresh produce or in the processedform. According to Chadha (2009) India loses about 35-45% of the harvested fruits andvegetables during handling, storage, transportation etc. leading to the loss of Rs. 40,000crores per year.

(b) Important sites of post-harvest losses: Important sites where post-harvest losses are noticedin India are —

• Farmer’s field (15-20%)• Packaging (15_20%)•. Transportation (30-40%)• Marketing (30-40%)

(c) Estimated loss of fruits

CropEstimated loss (%)

Papaya 40100%

Grapes 27%

Banana 20-28%

Citrus 20-95%

Avufado 43%

Apple 14%

Estimated loss of Vegetables

Onion25-40%

Garlic 08-22%

Potato 30-40°

Tomato 5-347%

Cabbage & cauliflower 7.08-25.0%

ChIli 4-35,0%

Radish 3-5%

Carrot 5-9%

(d) Causes of post-harvest losses: Horticultural crops not only provide nutritional andhealthy foods to human beings, but also generate a considerable cash income for growers.However, horticultural crops typically have high moisture content, tender texture and highperishability. If not handled properly, a high-value nutritious product can deteriorate androt in a matter of days or hours. The causes of post-harvest losses can be divided intodifferent categories:

1. MetabolicAll fresh horticultural crops are live organs. The natural process of respirationinvolves the breakdown of food reserves and the aging of these organs.

2. MechanicalOwing to their tender texture and high moisture content, fresh fruits and

vegetables are very susceptible to mechanical injury. Poor handling, unsuitablecontainers, improper packaging and transportation can easily cause bruising,cutting, breaking, impact wounding and other forms of injury.

3. Developmental

These include sprouting, rooting, seed germination, which lead to deterioration inquality and nutritional value.

4. Parasitic diseases

High post-harvest losses are caused by the invasion of fungi, bacteria, insects andother organisms. Micro-organisms attack fresh produce easily and spread quickly,because the produce does not have much of a natural defense mechanism and hasplenty of nutrients and moisture to support microbial growth.

5.Physiological deterioration

Fruits and vegetable cells are still alive after harvest and continue theirphysiological activity. Physiological disorders may occur due to mineraldeficiency, low or high temperature injury or undesirable atmospheric conditions,such as high humidity, physiological deterioration can also occur spontaneously byenzymatic action leading to over-ripeness and senescence, a simple agingphenomenon.

6. Lack of market demand

Poor planning pr inaccurate production and market information may lead to overproduction of certain fruits or vegetables which can’t be sold in time. Thissituation occurs most frequently in areas where transportation and storage facilitiesare inadequate. Produce may lie rotting in production areas, if farmers are unableto transport it to people who need it in distant locations.

7. Consumption

These losses can be due to inadequate preservation methods at home, methods ofcooking and preparation such as peeling, consumption styles etc.

8. Others

Lack of clear concept of packing house operations. Lack of awareness among the growers, contractors and even the policy makers.

Lack of infrastructure. Late realization of its importance,

Inadequate technical support. Wide gap in technologies available and in vogue. Inadequate post-harvest quality control.

Unorganized marketing. Absence of pre-cooling and cold storage.

Inadequate market facilities, market intelligence and market information service(MIS)

Poor storage facilities.

(e) Impact of post-harvest losses

Post harvest losses of horticultural crops affect both the nutritious status of the populationand economy of the country.Nutrition

Fruits and vegetables are rich source of vitamins and minerals essential for humannutrition. These are wasted in transit from harvest to consumer represent a loss in thequantity of a valuable food. This is important not only in quantitative terms, but also fromthe point of view of quality nutrition.

Economy

Careless harvesting and rough handling of perishable bruise and scar the skin, thusreducing quality and market price. Such damaged produce also fails to attract theinternational buyers, and bring the exporting country less profit and bad name. Thisultimately results in huge economic losses to the country.

For improving the situation, it is essential to create awareness among growers, farmworkers, manager’s traders and exporters about the extent of losses being incurred and theireconomic consequences. These groups of people involved in the fruit industry also need tolearn the basic principles of fruit handling and storage. In addition, the government needsto provide basic infra-structure like storage, handling, grading, packing, transport andmarketing facilities and technical expertise. This could be carried out by the public andprivate sectors.

(f) Technologies for minimizing the losses

Fruits and vegetables are perishable in nature. Scientific harvesting and handling are thepractical way to reduce the losses due to physical damage, spoilages, due to insect damagesand microbial growth. Various protocols are standardized and available for adoption to getthe best result, which will give economic benefits. Similarly, proper storage conditions,with suitable temperature and humidity are needed to lengthen the storage life and maintainquality once the crop has been cooled to the optimum storage tempera Lure. Greateremphasis need to be given on the training of farmers, creation of infrastructure for coldchain with common facilities for sorting, grading, packing and post harvest treatments in allmajor markets. Some technologies for extension of shelf life of fruits and vegetables are:

1. Waxing

It is used as protective coating for fruits and vegetables and help in reduction in lossin moisture and rate of respiration and ultimately results in prolonged storage life.

2. Evaporative cool storage

It is the best short-term storage of fruits and vegetables at farm level. It helps thefarmers to get better returns for their produce. In this structure, horticultural cropsreduce shriveling and extend their storage life.

3. Pre-packaging

This technology controls the rate of transpiration and respiration and hence keeps thecommodity in fresh condition both at ambient and low temperature. It can able tobring revolutionary progress in our trade practice and also benefit the consumer andthe producer because of its low cost and ready availability.

4. Cold storage

These structures are extensively used to store fruits and vegetables for a long periodand employ the principle of maintaining a low temperature, which reduces the rate ofrespiration and thus delays ripening.

5. Modified atmosphere packaging (MAP)

These packaging modify the atmosphere composition inside the package byrespiration. This technology is successful to extend the shelf life of (Cavendishbanana, carrots capsicum, green chilli and tomatoes by 15, 14, 13, 8 and 15 clays asagainst 5, 7, 8, 4 and 7 days in control respectively, under ambient conditions.Storage of Papaya can be extended 4 weeks when stored at 10 -12 °C under modifiedatmosphere (MA) conditions by wrapping them in low density polyethylene (LDPE)bag. Using this technique, the fruit can be transported to different markets inrefrigerated sea containers with Temperature Sea at 10-12 °C. Fruits ripen within 3-4days after arrival when placed at ambient temperature. While using optimum lowtemperature, storage life of Cavendish banana, capsicum, green chili and tomato canbe extended to 42,21,28 and 30 days in comparison to 21, 10,21 and 15 daysrespectively.

6. Controlled Atmosphere (CA) storage

It is based, on the principle of maintaining an artificial atmosphere in storage room,which has higher concentration of CO2 and lower concentration of 02 than normalatmosphere. This reduces the rate of respiration and thus delays aging. This methodof storage is very effective when combined with low temperature storage.

7. Irradiation

It is the newer technologies that can be gainfully employed during storage to reducepost-harvest losses and extend storage life of fruits and vegetable. When fruits andvegetables expose to ionizing radiation (such as gamma-rays) at optimum dosagedelays ripening minimizes insect infestation, retards microbial spoilages, controlsprouting, and rotting of onion, garlic and potato during storage. It is also used as adisinfection treatment and controls fruit fly on citrus, mango seed weevil and papayafruit fly.

8. Edible coatings

These are continuous matrices prepared from edible materials such as proteins,polysaccharides and lipids. They can be used as film wraps and when consumed withthe food, become an ingredient of the food. They not only minimize the post harvestlosses but also need for energy intensive operations and controlled atmospherestorage. They can control migration of gases, moisture, oil, fat, and solutes, as well asretain volatile flavouring compounds. An edible coating improves structural integrityand mechanical handling and carry product so that they help to maintain quality andinhibit microbial growth causing deterioration of the product.

9. Others Facilities/ services like grading, washing, cleaning, scientific harvesting and

the like, in respect of perishables at the farm level.

Cold storage facilities should be extended to tropical fruits and vegetables.Handling protocols should be established for crops other than mango, citrus,grapes and capsicurn to improve the shelf life and export.

The issue relating to increasing the shelf life of horticultural products needs tothe addressed.

Appropriate packaging material for export of fresh fruits, vegetables and formodified atmosphere packaging should be developed.

Value addition needs to be viewed in a wider perspective than mereprocessing to ensure better return to the producer/ farmer, besides providingbetter quality product to the consumer.

2. LECTURE NOTES

Maturity Indices, Harvesting and Post Harvest Handling of Fruits And Vegetables

I. MATURITY

It is the stage of fully development of tissue of fruit and vegetables only after which itwill ripen normally. During the process of maturation the fruit receives a regular supply of foodmaterial from the plant. When mature, the abscission or corky layer which forms at the stern endstops this inflow. Afterwards, the fruit depend on its own reserves, carbohydrates are dehydratedand sugars accumulate until the sugar acid ratio form. In addition to this, typical flavour andcharacteristic colour also develop. it has been determined that the stage of maturity at the time ofpicking influence the storage life and quality of fruit, when picked immature like mango developwhite patches or air pockets during ripening and lacking in normal brix acid ratio or sugar acidratio, taste and flavour on the other hand if the fruits are harvested over mature or full ripe theyare easy susceptible to microbial and physiological spoilage and their storage life is considerablyreduce. Such fruits persist numerous problems during handling, storage and transportation.Therefore, it is necessary or essential to pick up the fruits or vegetables at correct stage ofmaturity to facilitate proper ripening, distant transportation and maximum storage life.

Horticultural maturity

It is a developmental stage of the fruit on the tree, which will result in a satisfactoryproduct after harvest.

Physiological maturity

It refers to the stage in the development of the fruits and vegetables when maximumgrowth and maturation has occurred. It is usually associated with full ripening in the fruits. ThePhysiological mature stage is followed by senescence.

Commercial maturity

It is the state of plant organ required by a market. It commonly bears little relation toPhysiological maturity and may occur at any stage during development stage.

Harvest Maturity

It may be defined in terms of Physiological maturity and horticultural maturity, it is astage, which will allow fruits / vegetables at its peak condition when it reaches to the consumersand develop acceptable flavour or appearance and having adequate shelf life.

Table 1: Criteria of maturity for harvesting fruits and vegetables

Fruit Physical Chemical

Mango Olive green colour with clear lenticels, Starch content, flesh colour

shoulder development size sp. gravity,

days from fruit set.

Banana Skin colour, drying of leaves of the plant, Pulp/peel ratio, starch content

brittleness of floral ends, angularity of the

fruit, and days from emergence of

inflorescence.

Citrus Colour break of the skin from green to Sugar/acid ratio, TSS

orange, size

Grapes Peel colour, easy separation of berries, TSS 18-12 Thompson seedless,

characteristic aroma 12-14 for Bangalore Blue,

14-16 for Anab-e-shahi

Apple Colour size Firmness as measured by

pressure tester

Papaya Yellow patch or streaks. Jelliness of the seed, seed

colour

Vegetables are harvested at harvest maturity stage, which will allow it to be at its peakcondition when it reaches the consumer, it should be at a maturity that allows the produce todevelop an acceptable flavour or appearance, it should be at a size required by the market, andshould have an adequate shelf life. Time taken from pollination to horticultural maturity underwarm condition, skin colour, shape, size and flavour and abscission and firmness are used toassess the maturity of the produce.

Table 2: Time taken from pollination to horticultural maturity

S.No.Vegetables Time to harvest

Maturity (days)

1. Ridge gourd 5 -6

2. Squash 7 - 8

3. Brinjal 25 - 40

4. Okra 4 - 6

5. Pepper (green stage) 45 - 55

6. Pepper (red stage) 60 -70

7. Pumpkin (mature) 65 - 70

8. Tomato (mature green) 35 - 45

9. Tomato (red ripe stage) 45 - 60

10. Peas 30 - 35

Skin colour

Loss of green colour in citrus and red colour in tomato.

Shape, size and flavour

Sweet corn is harvested at immature stage, smaller cobs marketed as baby corn. Okra andcow pea are harvested at mature stage (pre fiber stage). In chilli, bottle gourd, bitter gourd,cluster beans maturity is related to their size. Cabbage head and cauliflower curd are harvestedbefore un pleasant flavour.

Abscission and firmness

Musk melon should be harvested at the formation of abscission layer. In cabbage andlettuce should be harvested at firmness stage.

Factors affecting maturity

1. Temperature: Higher temperature gives early maturity. e.g. Gulabi (Pink) grapes maturein 100 days in Western India but only 82 days are enough in the warmer Northern India.Lemon and guava takes less time to mature in summer than in winter. Sun-scorched portions of fruits are characterized by chlorophyll loss, yellowing,disappearance of starch and other alcohol insoluble material, increase in TSS content,decrease in acidity and softening.

2. Soil: Soil on which the fruit tree is grown affects the time of maturity. e.g. Grapes areharvested earlier on light sandy soils than on heavy clays.

3. Size of planting material: This factor in propagated fruits affects fruit maturity. e.g. Inpineapple, the number of days taken from flowering to fruit maturity was more byplanting large suckers and slips than by smaller ones.

4. Closer spacing: Close spacing of hill bananas hastened maturity.5. Pruning intensity: It enhanced the maturity of Flordasun and sharbati Peaches.6. Girdling: Process of constricting the periphery of a stem which blocks the downward

translocation of CHO, hormones, etc. Beyond the constriction which rather accumulatesabove it. In Grape vines it hastens maturity, reduces the green berries in unevenlymaturity cultivar and lowers the number of short berries. It is ineffective when done closeto harvest. CPA has an additive effect with girdling

MATURITY INDEX

Maturity index

The factors for determining the harvesting of fruits, vegetables and plantation cropsaccording to consumer’s purpose, type of commodity, etc and can be judged by visual means(colour, size, shape), physical means (firmness, softness), chemical analysis (sugar content, acidcontent), computation (heat unit and bloom to harvest period), physiological method(respiration).These are indications by which the maturity is judged. Various index are as Follows;

1. Visual indices

It is most convenient index. Certain signals on the plant or on the fruit can be used aspointers. E.g. drying of top leaves in banana, yellowing of last leaf of Peduncle in jackfruit. Flowof sap from cut fruit stalk of mango slows down if the harvest is done after maturity but in

immature fruits, exudation is more and comes with force in a jet form. in papaya, the latexbecomes almost watery. The flow gets reduced on maturity in Sapota. In fruits like banana andSapota, floral ends become more brittle and shed with a gentle touch or even on their own. InSapota, the brown scurf on the fruit skin starts propping. In mango, lenticels become moreprominent and the waxy bloom gradually disappears. Grapes develop translucent bloom. Otherchanges like angularity in banana, development of creamy wide space between custard applesegments and the flattening of the eyes in pineapple and tubercles in litchi serve as reliablematurity indices.

2. Seed development

It can also be used as an index of fruit maturity, e.g. endocarp hardening for stone andfiber development for dessert in mango.3. Start of bud damage

Occasionally it can be used as an index of fruit maturity in mango.

4. Calendar date

For perennial fruit crops grown in seasonal climate which are more or less uniform fromyear to year, calendar date for harvest is a reliable guide to commercial maturity. This approachrelies on a reproducible date for the time of the flowering and a relative constant growth periodfrom flowering through to maturity. Time of flowering is largely dependent on temperature, and

the variation in number of days from flowering to harvest can be calculated for somecommodities by use of the degree- concept.5. Heat units

Harvest date of newly introduced fruits in a widely varying climate can be predicted withthe help of heat unit. For each cultivar the heat requirement for fruit growth and development canbe calculated in terms of degree days: Maturity at higher temperature is faster as the heatrequirement is met earlier. This heat unit helps in planning, planting, harvesting and factoryprogrammes for crops such as corn, peas and tomato for processing.

MATURITY OF FRUITS AND VEGETABLES

Banana

The fruit is harvested when the ridges on the surface of skin change from angularity toround i.e. after the attainment of 3% full stages. Dwarf banana are ready for harvest within 11-14 months after planting while tall cultivars takes about 14-16 months to harvest. Peel colourchange from dark green to light green the remaining style ends were dry, and brittle and fruitswere less angular in shape.

Guava

TSS acid ratio, specific gravity and colour are determined the maturity in guava. For e.g.

Allahabad safeda - 35.81

Apple colour guava - 26.39

Chittidar guava - 28.13

Lucknow - 49 -34.25

Specific gravity - Less than I

Colour - Light green to yellow.

Ber

In ber maturity is judged by colour (yellow), specific gravity (less than 1) and TSS

Pomegranate

Sugar percentage should be 12-16% and acid percentage 1.5—2.5%, variety Ganeshharvest when seed colour becomes pink. In this stage TSS 12.5% and sugar acid ratio 19.5%.

Bael

It takes one year for fruiting after flowering. It is the fruit which ripen after one year offlowering. April start harvesting and may end it start in flowering.

Mango

This can be judged when one or two mangoes ripen on the tree are fall on the ground oftheir own accord. This process of fallen is known as tapaca specific gravity 1,01—1.02 andTSS 10-14%.

Table 3 Maturity indices of vegetable crops

Root, bulb and tuber crops Maturity indices

Radish and carrot Large enough and crispy

Potato, onion and garlic Tops beginning to dry and topple clown

Yams, bean and ginger Large enough

FRUIT VEGETABLES

Cowpea, snap bean, sweet pea, Well filled pods that snap readily

winged bean

Lima bean and pigeon pea Well filled pods that are beginning to lose their

greenness.

Okra Desirable size reached and the tips of which can be

snapped readily

Snake gourd Desirable size reached and thumbnail can still

penetrate flesh readily

Egg plant, bitter gourd, slicing Desirable size reached but still tender

cucumber

Tomato Seeds slipping when fruit is cut, or green colour

turning pink

Muskmelon Easily separated from vine with a slight twist leaving

clean cavity (full slip stage).

Watermelon Dull hollow sound when thumped

FLOWER VEGETABLES

Cauliflower Curd compact

Broccoli Bud cluster compact

II. HARVESTING

The goals of harvesting are to gather a commodity from the field at the proper level ofmaturity with a minimum of damage and loss, as rapidly as possible and at a minimum cost. Thisis achieved through hand-harvesting in most fruit, vegetable and flower crops.1. Hand Harvesting

Hand harvesting has a number of advantages over machine harvest. People can accuratelydetermine product quality, allowing accurate selection of mature product. This is

particularly important for crops that have a wide range of maturity and need to be harvestedseveral times during the season. Properly trained workers can pick and handle the product with aminimum of damage. Many fresh-market products have a short shelf life if they are bruised ordamaged during harvest and handling. The rate of harvest can easily be increased by hiring moreworkers. Hand- harvesting also requires a minimum of capital investment. The main problemwith hand harvesting is labor management. Labor supply is a problem for growers who cannotoffer a long employment season. Labor strikes during the harvest period can be costly. In spite ofthese problems, quality is so important to marketing fresh- market commodities successfully thathand harvesting remains the dominant method of harvest of most fruits and vegetables and for allcut flowers.

Effective use of hand labor requires careful management. New employees must betrained to harvest the product at the required quality and at an acceptable rate of productivity.Employees must know what level of performance and must be encouraged and trained to reachthat level.

2. Mechanical Harvesting

Mechanical harvest is currently used for fresh-market crops that are roots, tubers, orrhizomes and for nut crops. Vegetables that are grown below ground (radishes, potatoes, garlic,carrots, beets and others) are always harvested only once and the soil can be used to cushion theproduct from machine caused mechanical injury. Tree nuts and peanuts are protected by a shelland easily withstand mechanical handling. A number of products destined for processing such astomatoes, wine grapes, beans, peas, prunes, peachesand some leafy green vegetables are machineharvested because harvest damage does not significantly affect the quality of processed product.This is often because the product is processed quickly after harvest. These crops have also beenamenable to new production techniques and breeding that allow the crop to be better suited tomechanical harvest.

The main advantage of mechanical harvest equipment is that machines can often harvestat high rates. Tree nut harvesters, for eg. attaching a shaking mechanism to the tree and removemost of the nuts in few seconds. The nuts are either caught on a fabric- covered frame or pickedup from the ground by other machines. This allows an orchard to be harvested very quicklycompared to handshaking with poles. Machine harvest also reduces management problemsassociated with workers. The commodity must be grown to accept mechanical harvest.

Demerits of Mechanical Harvesting

Machines are rarely capable of selective harvest. Mechanical harvesting will not befeasible until the crop or production techniques can be modified to allow one time harvest.Harvesting machines often causes excessive product perennial crops eg. Bark damage from a treeshaker. The harvesting machines are quite expensive.

III. POST HARVEST HANDLING

Being living organs, fruits and vegetables continue to respire even after harvesting whenthey have a limited source of food reserves. In addition to degradation of respiratory substrates, anumber of changes in taste, colour, flavour, texture and appearance take place in the harvestedcommodities which make them unacceptable for consumption by the consumers if these are nothandled properly. Post harvest technology starts immediately after the harvest of fruits andvegetables. The whole process of processing the commodities is categorized as Handling of freshproduce. Post harvest Technology of fresh fruits and vegetables combines the biological andenvironmental factors in the process of value addition of a commodity.

1. Precooling

Precooling (prompt cooling after harvest) is important for most of the fruits andvegetables because they may deteriorate as much in 1 hr at 32°C. In addition to removal of fieldheat from commodities, precooling also reduces bruise damage from vibration during transit.Cooling requirement for a crop vary with the air temperature during harvesting, stage of maturityand nature of crop.

There are many methods of precooling viz, cold air (room cooling, forced air cooling),cold water (hydrocooling), direct contact with ice (contact icing), evaporation of water from theproduce (evaporative cooling, vacuum cooling) and combination of vacuum and hydrocooling(hydrovac cooling). Some chemicals (nutrients/growth regulators/ fungicides) can also be mixedwith the water used in hydrocooling to prolong the shelf life by improving nutrient status of cropand preventing the spread of post harvest diseases.

2. Washing, Cleaning and Trimming

Before fresh fruits and vegetables are marketed various amounts of cleaning arenecessary which typically involves the removal of soil dust, adhering debris, insects and sprayresidues. Chlorine in fresh water is often used as disinfectant to wash the commodity. Somefungicides like Diphenylamine (0.1 - 0.25%) or ethoxyquin (0.2 - 0.5%) may be used as postharvest dip to control the disorders. Eg. Apple superficial scald. For cleaning of some fruit typevegetables (melons, brinjals, tomatoes, cucumber) they should be wiped with damp cloth. Manyvegetable need trimming, cutting and removal of unsightly leaves or other vegetative parts.

3. Sorting, Grading and Sizing

Sorting is done by hand to remove the fruits which are unsuitable to market or storagedue to damage by insects, diseases or mechanical injuries. The remainder crop product isseparated into two or more grades on the basis of the surface colour, shape or visible defects. Foreg, in an apple packing house in India 3 grades viz. Extra Fancy, Fancy and standard may bepacked for marketing. The fourth “cull” grade is meant for processing. After sorting and grading,sizing is done either by hand or machine. Machine sizers work on two basic principles: weightand diameter. Sizing on the basis of fruit shape and size are most effective for spherical

(Oranges, tomato, certain apple cultivars) and elongated (Delicious apples and European pears orof non-uniform shape) commodities, respectively.

4. Curing

Curing is an effective operation to reduce the water loss during storage from hardyvegetables viz, onion, garlic, sweet potato and other tropical root vegetables. The curing methodsemployed for root crops are entirely different than that from the bulbous crops (onions andgarlic). The curing of root and tuber crops develops periderms over cut, broken or skinnedsurfaces wound restoration. It helps in the healing of harvest injuries, reduces loss of water andprevents the infection by decay pathogens.

Onions and garlic are cured to dry the necks and outer scales. For the curing of onion andgarlic, the bulbs are left in the field after harvesting under shade for a few days until the greentops, outer skins and roots are fully dried.5. Waxing

Quality retention is a major consideration in modem fresh fruit marketing system. Waxesare esters of higher fatty acid with monohydric alcohols and hydrocarbons and some free fattyacids. But coating applied to the surface of fruit is commonly called waxes whether or not anycomponent is actually a wax. Waxing generally reduces the respiration and transpiration rates,but other chemicals such as fungicides, growth regulators, preservative can also be incorporatedspecially for reducing microbial spoilage, sprout inhibition etc. However, it should beremembered that waxing does not improve the quality of any inferior horticulture product but itcan be a beneficial adjunct to good handling.

The advantages of wax application are:

-Improved appearances of fruit.

-Reduced moisture losses and retards wilting and shrivelling during storage of fruits.

-Less spoilage specially due to chilling injury and browning.

-Creates diffusion barrier as a result of which it reduces the availability of 02 to thetissues thereby reducing respiration rate.

-Protects fruits from micro-biological infection.

-Considered a cost effective substitute in the reduction of spoilage when refrigeratedstorage is unaffordable.

-Wax coating are used as carriers for sprout inhibitors, growth regulators andpreservatives.

The principal disadvantage of wax coating is the development of off- flavour if notapplied properly. Adverse flavour changes have been attributed to inhibition of O2 andCO2 exchange thus, resulting in anaerobic respiration and elevated ethanol and acetaldehydecontents. Paraffm wax, Carnauba wax, Bee wax, Shellac, Wood resins and Polyethylene waxes

used commercially.

6. Packaging

Proper or scientific packaging of fresh fruits and vegetables reduces the wastage ofcommodities by protecting them from mechanical damage, pilferage, dirt, moisture loss andother undesirable physiological changes and pathological deterioration during the course ofstorage, transportation and subsequent marketing. For providing, uniform quality to packedproduce, the commodity should be carefully supervised and sorted prior to packaging. Packagingcannot improve the quality but it certainly helps in maintaining it as it protects produce againstthe hazards of journey. Striking developments have been in the field of packaging ofhorticultural produce and the gunny bags, grasses and stem leaves used so far for packaging arenow being replaced by a variety of containers such as wooden boxes, baskets woven frombamboo or twigs, sack/jute bags and corrugated fibre board (CFB) boxes.

7. Storage

A number of storage techniques (ground storage, ambient storage, refrigerated storage,air cooled storage, zero energy storage, modified atmospheric storage, hypobaric storage andcontrolled atmosphere storage) are being used for fruits and vegetables depending upon thenature of the commodity and the storage period intended.

3. LECTURE NOTES

Ripening Process, Changes Occurring during Ripening, Respiration and Factor affectingRespiration Rate

Fruit Ripening

Fruit ripening is a genetically programmed stage of development overlapping withsenescence. The fruit is said to be ripe when it attains its full flavour and aroma and othercharacteristics of the best fruit of that particular cultivar. The words “mature “and “ripe” areessentially synonymous when used to describe these fruits that ripe on the plants known as non-climacteric. However, in case of climacteric fruits a mature fruit require period before attaining adesirable stage of edibility.

Table 1. List of climacteric and non-climacteric fruits

Changes during Fruit Ripening

1. Cell Wall ChangesCell wall consists of pectic substances and cellulose as the main components alongwith

sma1amounts of hemicellulose and non-cellulosic polysaccharides. In cell wall, the changesparticularly in the middle lamella which is rich in pectic polysaccharides are degraded andsolubilised during ripening. During this softening, there is a loss of neutral sugars (galactoseand arabinose-major components of neutral protein) and acidic pectin (rhamnogalacturonan) ofall cell wall. The major enzymes implicated in the softening of fruits are pectine1asterase,polygalacturonase cellulase and β- galactosidase.

2. Starch

During fruit ripening sugar levels within fruit tend to increase due to either increased sugarimportation from the plant or to the mobilization of starch reserves within the fruit, depending onthe fruit type and whether it is ripened on or off the plant. With the advancement of maturity, theaccumulated starch is hydrolysed into sugars (glucose, fructose or sugars) which are known as acharacteristic event for fruit ripening. Further breakdown of sucrose into glucose and fructose isprobably mediated by the action of invertase. In vegetables like potato and peas on the otherhand, the higher sucrose content which remains high at fresh immature stage, converts into starchwith the approach of maturity.

3. Organic Acids

With the onset of fruit ripening there is downward trend in the levels of organic acids. Thedecline in the content of organic acids during fruit ripening might be the result of an increase inmembrane permeability which allows acids to be stored in the respiring cells, formation of saltsof malic acid, reduction in the amounts of acid translocated from the leaves,

reduced ability of fruits to synthesize organic acids with fruit maturity, translocation into sugarsand dilution effect due to the increase in the volume of fruit.

4. Colour

With the approach of maturation, the most obvious change which take place is thedegradation of chlorophyll and is accompanied by the synthesis of other pigments usually eitheranthocyanins or carotenoids. They can give rise to a wide range of colours (from red to blue).The chloroplasts in green immature fruit generally lose chlorophyll on ripening and change intochromoplasts which contain carotenoid pigments. Carotenoids are normally synthesized in greenplant tissue a major product being 3-carotene. However, in many fruits additional - carotene andlycopene is synthesized during ripening.

5. Flavouring Compounds

Although fruit flavour depends on the complex interaction of sugars, organic acids,phenolics and volatile compounds but the characteristic flavour of an individual fruit orvegetable is derived from the production of specific flavouring volatile. These compounds aremainly esters, alcohols, aldehydes, acids and ketones. At least 230 and 330 different compoundsin apple and orange fruits have been indicated respectively.

6. Ascorbic Acid

L-ascorbic acid (Vitamin C) is the naturally occurring ascorbic acid in fruits. A reducedamount of ascorbic acid is noticed in pome, stone and berry fruits at the time of harvest. Anincrease in ascorbic acid content with the increase in fruit growth has been and the levelsdeclined with the advancement of maturity and onset of fruit ripening in pear, sweet potatoes,potato, asparagus and okra during the course of post harvest handling.

7. Phenolics

The phenolic content of most fruits declines from high levels during early growth to lowlevels when the fruit is considered to be physiologically mature and thereafter susceptible to theinduction of ripening.

8. Amino Acids and Proteins

Decrease in free amino acid which often reflects an increase in protein synthesis. Duringsenescence the level of free amino acids increases reflecting a breakdown enzymes anddecreased metabolic activity.

9. Ethylene Production and Respiration

Physiological events responsible to ripening process are as follows

(1) Ethylene production

(2) Rise in respiration

Ethylene production

In climacteric fruits such as mango, banana, ethylene production increase and causes:

Rise in respiration Rise in temperature

Rise in activity of hydrolytic enzymes.

Ethylene is produced from an essential amino acid — methionine. Following the steps as

below:

Rise in respiration

Respiration is required for releasing energy and the substrate for synthesis of severalorganic compounds required in the ripening process. During ripening in climacteric fruits, thereis rise in respiration called climacteric. The clirnacteric peak is obtained very fast whentemperature is relatively high. Respiration is a most deteriorating process of the harvested fruitsand vegetables which leads to the oxidative breakdown of the complex materials (carbohydratesor acids) of cell into simpler molecules (CO2 and water) with the concurrent production ofenergy required by the cell for the completion of chemical reactions. In brief, the process ofrespiration can be summed up with the following reaction:

C6H1206 +6O2 6 CO2 + 6 H20+ energy

4. LECTURE NOTES

Use of Chemicals for Increasing Shelf Life of Fruits and Vegetable

(A) Ethylene absorbent

Ethylene is responsible for decreasing shelf life. Putting KMNO4 @ 100 ppm soaked filterpaper can minimized ripening and increase shelf life. In Banana this method is very useful.

(B)Antifungal Agents

•SOPP: Sodium orthophenylphenate

•Diphenyl wraps protection against moulds, stem-end rot.

•Dibromoletrachloroethane and esters give better flavour.

(C)Use of Inhibitors

Treatment Crop Chemical Concentration

Post-harvest Mango MH 1000-2000 ppmAfter fruit formation Apple 2-Dimethyl-hydrazide 10,000 ppm

(D) Use of Auxins

Also helpful to advance in ripening and may increase shelf life.

Chemical Concentration Crop Stage

2,4-D 5 ppm Grape Pre-harvest2,4,5-T 25 ppm Fig Pre-harvest2,4,5-T 100 ppm Mango After harvesting

E)Vegetables can be preserved by lactic acid and may increase the shelf life.

F)Post harvest dipping of papaya fruits either in l00 ppm GA3 or CaCl2 al 2% extended shelf lifeup to 9 days without any decline in quality.

Factors affecting ripening can be physiological, physical, or biotic.

Physiological factors relate to fruit maturity or environmental factors, which affect themetabolism of fruit and banana.

Physical factors include mechanical damage, or relate to dimensions of the fruit.Biotic factors include attack from pests and diseases.

Fruit maturity

The more mature fruit is at harvest, the shorter the ripening period. Studies show that bananaharvested 100 days after flowering ripened in 11 days. When the same cultivar was harvested 90days after flowering, the ripening period increased to 15 days, and further increased to 22 dayswhen the fruit was harvested at 80 days. Farmers have to match the date of harvest with thetransportation time to the market. However, an early harvest reduces yield.

Cross section of immature and mature banana fruits

As fruits mature, the cross-sectional diameter increases. Fruit angularity also changes duringgrowth and maturation. As fruits approach full maturity, fruit angles become less acute Fruitangularity can be used to predict the optimum harvest date of banana.

Temperature

Physiological studies on bananas show that storage life decreases as external temperatureincreases over the range 15-35ºC. A 1ºC reduction increases storage period by 1-2 days.

The relationship between ripening period and temperature is due to fruit respiration. Fruitrespiration depends on many enzymatic reactions, and the rate of these reactions increasesexponentially with increase in temperature. Studies show that ripe fruits respire at approximately4 times the rate of unripe fruits. Consequently, ripe fruits lose sugar resources at a higher ratethan unripe fruits. This explains why ripe fruits deteriorate quickly.

The relationship between temperature and respiration is described mathematically by van't Hoff'stemperature quotient (Q10). van't Hoff showed that the rate of respiration approximately doublesfor each 10ºC rise in temperature.

Water loss and humidity

Where fruit is sold on a weight basis, loss of water means economic loss. Additionally, waterloss reduces visual quality. Water loss causes fruit to lose its firmness, the peel becomes soft andshriveled, and ripening period reduces. Studies on fruits show a curvilinear or power relationshipbetween fruit weight loss and ripening period. For a 2% change from 2% to 4% weight loss perday, ripening period reduced by 9 days or 50%. Therefore, at a low rate of weight loss, a smallincrease in weight loss has a critical effect on ripening.The rate of water loss depends on the ambient relative humidity (RH). RH is the amount of watervapor present in the air, relative to the maximum amount of water vapor that can be held in theair, at a given temperature, saturated air being 100% RH. When a water-containing material suchas fruit is placed in an enclosed space, for example, a sealed container, the water content of theair within the container increases or decreases until it is in equilibrium with the fruit.

The water equilibrium principle applies when fruit is stored. The rate of water loss depends onthe ambient RH. At an ambient RH of 95-100%,fruit loses little or no moisture, and ripening period is unaffected. However, as humiditydecreases, the rate of water loss increases, and ripening period reduces.

Excessive wetting can also be a problem. When fruit is stored in wet conditions, such as in moistcoir (coconut fiber), the uptake of water from the coir to the fruit leads to peel splitting.

SunlightExposure to direct sunlight reduces the ripening period of fruits. Sunlight increases fruit

temperature above ambient temperature, which increases respiration, and possibly the rate ofwater loss. The solar radiation that falls upon foods held in direct sunlight increases thetemperature above the ambient temperature. The amount of increase in temperature depends onthe intensity of the radiation, the size and shape of the food' and the duration of exposure to thedirect rays of the sun. The intensity of solar radiation depends upon latitude, altitude, season ofthe year, time of day, and degree of cloud cover.

Altitude

Within a given latitude the prevailing temperature is dependent upon the elevation when otherfactors are equal. There is on the average a drop in temperature of 6.5°C for each Km increase inelevation above sea level. Storing food at high altitudes will therefore tend to increase the storagelife and decrease the losses in food provided it is kept out of the direct rays of the sun.

Atmosphere

The normal atmosphere contains by volume, approximately 78% nitrogen, 21% oxygen, 1%argon, 0.03% carbon dioxide' various amounts of water vapor and traces of inert gases.Modifying the atmosphere can improve the shelf life and reduce wastage of certain foods.

One type of controlled atmosphere storage (CA) is refrigerated storage in which the level ofoxygen is reduced to about 3% with the carbon dioxide content being raised to 1 to 5%,depending on the commodity. This CA storage may double the storage life over that of regularcold storage for certain varieties of apples and pears by slowing down the natural rate ofrespiration.Ethylene (C2H4) is a gaseous plant hormone which determines the time between harvest andsenescence. The time from harvest to the climacteric respiratory response is called the 'green life'or preclimacteric period. Ethylene shortens the preclimacteric period; at high concentrations,ethylene causes rapid initiation of the climacteric respiratory response and accelerates ripening.

When nonclimacteric fruits are exposed to ethylene, fruits show an increased rate of respiration.However, respiration rate falls when ethylene is removed. A rise in respiration rate may occurmore than once in nonclimacteric fruits. However, for climacteric fruits, the climacteric isautocatalytic, that is, once started, the process cannot be stopped until the fruit is ripe.

Poor storage methods allow a buildup of ethylene, stimulate the climacteric response, and reducethe ripening period. For example, plastic sheets placed over stacks of fruit for shade increase thelevel of ethylene within the fruit stack and increase the rate of ripening. Therefore, store fruit inthatched or ventilated areas to prevent the buildup of ethylene. Also, do not store unripe fruitswith ripe fruits.

During the preclimacteric period, fruits are less susceptible to physical damage and pathologicalattack. This is the best time for handling, transportation, and marketing.

Mechanical damage

Mechanical damage is a physical factor affecting ripening. Fruit damage during handlinggenerates ethylene. If ethylene production is sufficient to start the climacteric respiratoryresponse, fruit immediately starts to ripen.

Damage can also reduce ripening period by causing moisture loss. The effect of damage caneasily be measured by recording fruit weight loss over time. Cuts and abrasions on the surfacemembrane cause the most weight loss.After harvest, fruits lose the ability to repair ruptured peel. Harvesting techniques which damagefruit reduce storability.

Studies show that an abrasion affecting 5-10% of the peel can reduce the ripening period by40%. Damage can also lead to secondary infection, which increases the rate of water loss andfurther reduces quality.

Surface to volume ratio

The ratio between surface area and volume determines the rate of water loss. The greater thesurface to volume ratio, the shorter the postharvest life. A leaf which has two large surfaces withlittle volume loses moisture faster than a fruit. Large fruits lose less water than small fruits.

Peel thickness

Fruits with thin peel lose more water. A higher peel permeability leads to a higher rate of waterloss and a faster ripening rate. Also, fruits with thick peel, for example melons, withstanddamage better than fruits with thin peel, such as tomatoes.

Stomatal density

A higher density of stomata may cause a higher rate of water loss, which accelerates ripening.

Biotic stress. Fungi, bacteria, viruses, and insects also account for a considerable proportion of totalpostharvest loss. Pests and diseases reduce both ripening period and overall quality. However,attack by pests and diseases is often secondary because a pest exploits a damaged area of thefruit. Careful fruit handling often prevents such attacks.

5. LECTURE NOTES

Pre Harvest Factors Affecting Quality

Quality of post harvest product

Post harvest quality represents market quality, edible quality, transport quality, tablequality, nutritional quality, internal quality and appearance quality. Quality means a combinationof characteristics, attributes and properties that gives the values to human and enjoyments.Consumers consider good quality in relation to colour, flavour and nutrition. Quality of theproduce is the final manifestation of inter-relation between the commodity and its environment.The genetic characteristics and physiological status of the commodity determine the typical post-harvest behavior and quality of the produce and these two are the major bases for theinteraction. Pre-harvest factors viz, environmental factors such as temperature, relative humidity,water potential, light, cultural practices and pest management techniques determined the inherentquality of the produce. However, the ultimate quality is the final manifestation of inter relationbetween the commodity and its environment.

Several pre-harvest and post-harvest factors affect the quality of horticultural crops. Some ofthese factors are related to plant, others are related to environment or to cultural practices.

A. Pre-harvest factors

a) Related to plants

Crops: Quality of the fruit and vegetables are varies from crop to crop e.g. jackfruit, bael, potato,onion, pumpkin, garlic etc. having good quality in relation to shelf life, while apple, mango,cherry, strawberry, tomato, capsicum, okra, brussels sprout, chinese cabbage, carrot, radishattract more to consumers due to their attractive appearance.Cultivars: The quality of seed or plant material is an important factor that controls the quality

of the fruit and vegetable produced. Several parameters of quality are controlled genetically.

Cultural practices: All cultural practices have direct effect on the final quality of the produce.

Planting period: Many plants are very sensitive to environmental conditions, and thus qualitywill not be optimized when crop is produced under adverse conditions. Producing summer plantsduring the winter or vice-versa will not be appropriate, unless protection practices areimplemented.

Planting density: It affects both the quantity and quality of the produce. High density plantingincreases competition between plants, reduces light availability, and thus may decreasequantity. Low density planting lead to large size, better colored fruit or vegetable which mayhave shorter shelf life. Larger fruits are commonly more sensitive to physiological disorders.Irrigation: Irregular watering usually reduces fruit size, increases splitting, physiologicaldisorders, reduces water content in the plant or plant part, etc.Fertilization: Poor management of fertilizers will increase physiological disorders due todeficiencies of some minerals or increase of other leading to toxicity. In both cases, quality willbe negatively affected.

Pruning: It reduces the load and increases the growth of fruit and chemical use after harvest.

Thinning: This operation reduces the competition between fruits or plants and thus promotes

a good balance between the vegetative and fruit parts and improves quality.

Protection: Pathogens and insects have a very negative effect on quality. Poor management ofplant protection programmes can lead to very poor quality and reduced yield.

b) Related to environments

Temperature is the most important environmental factor that affects quality, very low orvery high temperature may injure sensitive crops. Adequate high intensity and quality isimportant for the formation of some colour. Wind and rain may cause negative effects on somecrops.

c) Related to chemicals

Many hormones and growth regulators are used in agriculture and they can affect qualityin different ways.

B) During harvest factor•Season: Quality of produce are greatly influenced by season e.g. Winter season harvest havingmore shelf life as compared to other season, while off season fruits and vegetables give moreremunerative price. Harvesting during or immediately after rains should not be carried out sinceit creates most favourable conditions for multiplication of micro-organisms. Citrus fruits becomesusceptible to damage if harvested during rains as their rind becomes turgid and prone to easybruising, sun-scald etc.

•Time: Fruits and vegetables should always be harvested when temperature is mild. Because,higher temperature leads to faster respiration. Morning harvest of horticultural crop prefer forlocal market because they are fully fresh and turgid and having dew drop in this time. Eveningharvesting is preferred for distant market due to higher accumulation of reserved carbohydratesand less amount of moisture which give the better quality of the produce to consumer. Leafyvegetables harvested in the latter part of the morning or late in the afternoon, the petioles of thesevegetables break less easily and their leaves are more resistant to tearing, since they

have lost water through transpiration and therefore are less brittle. Cucumber is harvested in thelate morning when it to be transported under less than ideal condition because it is less prone toinjury when it contains less water.•Method of harvesting: Selection of suitable method for harvesting of the produce is necessaryotherwise bruises or injuries during harvesting may later manifest as black or brown patchesmaking them unattractive. Latex coming out of stem in mango should not be allowed to fall onfruits as it creates a black spot. Injury to peel may become an entry point for microorganisms,causing rotting. Some harvesting gadgets have been developed, e.g. mango harvester in Lucknow(CISH).•Stage of harvesting: Fruits and vegetables must be harvested at right stage of maturity. A verycommon cause of poor product quality at harvest and rapid deterioration thereafter is harvestingimmature vegetables. Vegetables harvested immature or over mature usually do not keep long.Fruit vegetables harvested too early lose water fast and are more susceptible to mechanicaldamage and microbial attack. An over mature vegetable is more susceptible to decay, has passedits best eating quality, and deteriorates fast.

•Consumer demand: Harvesting time and harvest maturity can be altered by the requirement

of the consumer’s demand which may affect the quality of the produce at some extent.

c) Post-harvest factors:•Curing: Curing is done immediately after harvesting. It strengthens the skin. The process isinduced at relatively higher temperature and humidity, involving suberization of outer tissuesfollowed by the development of wound periderm which acts as an effective barrier againstinfection and water loss. It is favoured by high temperature and high humidity. Potato, sweetpotato, colocasia, onion and garlic are cured prior to storage or marketing. Potato tubers are heldat 18°C for 2 days and then at 7°—10°C for 10—12 days at 90% relative humidity. Curing alsoreduces the moisture content especially in onion and garlic. Drying of superficial leaves of onionbulbs protects them from microbial infection in storage.

•Degreening: It is the process of decomposing green pigment (Chlorophyll) in fruits usuallyapplying ethylene or similar metabolic inducers to fruit. It is applicable to banana, citrus andtomato. Degreening is carried out in special treating rooms with controlled temperature andhumidity in which low concentration of ethylene (20 ppm) is applied.

•Pre-cooling: High temperatures are detrimental to keeping quality of fruits and vegetables,especially when harvesting is done during hot days. Pre-cooling is a means of removing the fieldheat. It slows down the rate of respiration, minimizes susceptibility to attack of micro-organisms, and reduces water loss. Peas and okra which deteriorate fast need prompt pre-cooling.Washing and drying: Most of the fruits and vegetables are washed after harvesting to improvetheir appearance, to prevent wilting and to remove primary inoculum load of microorganism.Hence, a fungicide/bactericide should be used in washing water. Washing, improves shelf life ofbananas by delaying their ripening. After washing, excess of water should

be removed which would otherwise encourage microbial spoilage.

•Sorting and grading: Fruits and vegetables require sorting and grading for uniform packing atfield level. Sorting is done on the basis of size and colour while grading practice is performed asper the defect or on the basis of marketable and unmarketable produce.

•Disinfection: Papaya, mango, melon and other fruits are susceptible to fruit fly attack.Disinfection is done either by vapour heat treatment (VHT) at 43°C with saturated air with watervapour for 6-8 hr by Ethylene dibromide fumigation.

•Waxing: Fruits and vegetables have a natural layer on their outer surface which is partlyremoved by washing. An extra discontinuous layer of wax applied artificially with sufficientthickness and consistency to prevent anaerobic condition within the fruits provides necessaryprotection against decay organism. Waxing also improves the appearance and glossiness, makingthem more acceptable.

•Packing: It means more than carrying multiples of an object. Packing not only protects thehorticultural produce but also makes a favourable impression on the buyers and May able tofetch higher income.

•Delivery: Moving the harvest produce from the farm to the customer in good condition isimportant. All efforts upto delivery can be invalid if the fresh fruits and vegetables reach thedestination in poor condition. Care should be taken to protect the produce and it becomesnecessary when mixing load of fruits and vegetables to prevent violating the compatibilityfactors.

FACTORS RESPONSIBLE FOR DETERIORATION OF HARVESTED FRUITS ANDVEGETABLES

A- Primary causes of loss: Those are directly affect the food Enzymic changes

Enzymes which are endogenous to plant tissues can have undesirable or desirable consequences.

Examples involving enzymic changes include: The post-harvest spoilage of fruit and vegetables Oxidation of phenolic substances in plant tissues by phenolase (leading to browning) Sugar - starch conversion in plant tissues by amylases Post-harvest demethylation of pectic substances in plant tissues (leading to softening of

plant tissues during ripening, and firming of plant tissues during processing).

The major factors useful in controlling enzyme activity are:

1.temperature

2.water activity

3.pH

4.chemicals which can inhibit enzyme action

Chemical changes

Sensory quality

The two major chemical changes which occur during the processing and storage of foods andlead to a deterioration in sensory quality are lipid oxidation and non-enzymatic browning.Chemical reactions are also responsible for changes in the colour and flavour of foods duringprocessing and storage.

Lipid oxidation rate and course of reaction is influenced by light, local oxygenconcentration, high temperature, the presence of catalysts (generally transition metalssuch as iron and copper) and water activity. Control of these factors can significantlyreduce the extent of lipid oxidation in foods.

Non-enzymic browning is one of the major causes of deterioration which occurs duringstorage of dried and concentrated foods.

Colour changes

Almost any type of food processing or storage causes some deterioration of thechlorophyll pigments. This reaction is accelerated by heat and is acid catalysed.

Flavour changes

In fruit and vegetables, enzymically generated compounds derived from long-chain fattyacids play an extremely important role in the formation of characteristic flavors. Inaddition, these types of reactions can lead to significant off-flavors.

The permeability of packaging materials is of importance in retaining desirable volatilecomponents within packages, or in permitting undesirable components to permeatethrough the package from the ambient atmosphere.

Nutritional quality

The four major factors which affect nutrient degradation and can be controlled to varyingextents by packaging are

1.Light

2.oxygen concentration

3.temperature

4.water activity.

Physical changes

One major undesirable physical change in food is the absorption of moisture as a consequence ofan inadequate barrier provided by the package; this results in caking. It can occur either as a

result of a poor selection of packaging material in the first place, or failure of the packageintegrity during storage. In general, moisture absorption is associated with increasedcohesiveness.Biological changes

Microbiological

Micro-organisms can make both desirable and undesirable changes to the quality of foodsdepending on whether or not they are introduced as an essential part of the food preservationprocess or arise unintentionally and subsequently grow to produce food spoilage.

The two major groups of micro-organisms found in foods are bacteria and fungi, the latterconsisting of yeasts and moulds. Bacteria are generally the fastest growing, so that in conditionsfavourable to both, bacteria will usually outgrow fungi.

Foods are frequently classified on the basis of their stability as non- perishable, semi-perishable and perishable.The protection of packaged food from contamination or attack by micro- organisms depends onthe mechanical integrity of the package (e.g. the absence of breaks and seal imperfections), andon the resistance of the package to penetration by micro-organisms.

Macrobiological

Insect Pests

Warm humid environments promote insect growth, although most insects will not breed if thetemperature exceeds about 35 C° or falls below 10 C°. Also many insects cannot reproducesatisfactorily unless the moisture content of their food is greater than about 11%.

Rodents

Rats and mice carry disease-producing organisms on their feet and/or in their intestinal tracts andare known to harbour salmonella of serotypes frequently associated with food-borne infections inhumans.

B- Secondary causes of loss: Those lead to conditions that encourage a primary cause ofloss such as:

1- Inadequate harvesting, packaging and handling skills.2- Lack of adequate containers for the transport and handling of perishables.

3- Storage facilities inadequate to protect the food.

4- Transportation inadequate to move the food to market before it spoils.

5- Inadequate refrigerated storage.

6- Inadequate drying equipment or poor drying season.

7- traditional processing and marketing systems can be responsible for high losses.

8- Legal standards can affect the retention or rejection of food for human use.

10- Knowledge of management is essential for maintaining tool in good condition duringmarketing and storage.

11- Bumper crops can overload the post-harvest handling system or exceed the consumptionneed and cause excessive wastage.

Sites of losses

1. Losses may occur anywhere from the point where the food has been harvested orgathered up to the point of consumption. Losses can occur during one of the followingprocesses:

2. Harvest: The separation of the commodity from the plant that produced it.

3. Preparation. : The preliminary separation or extraction of the edible from the non- edibleportion.

4. Preservation: The prevention of lose and spoilage of foods. For example, the sun-drying of fruit, the use of refrigeration and the use of fungicides to inhibit mold growth infruits.

5. Processing : The conversion of edible food into another form more acceptable or moreconvenient to the consumer, for example, the manufacture of fruit juice and the canningof fruits and vegetables.

6. Storage: The holding of foods until consumption. Most storage is common storage(ambient temperature) but there are extensive storage capacities that can hold food underrefrigerated or controlled atmosphere conditions.

7. Transportation: All forms of transportation are used to convey foods from the point ofproduction to the ultimate point of consumption.

6. LECTURE NOTES

(Prepared By : Dr. Rajesh Singh)

Postharvest disease and Disorders

Postharvest disease may occur at any time during postharvest handling, from harvest toconsumption. Losses caused by postharvest diseases are greater than generally realizedbecause the value of fresh fruits increases several fold while passing from the field to theconsumer. Postharvest losses are estimated to range from 10 to 30% per year despite the useof modern storage facilities and techniques. When estimating postharvest disease losses, it isimportant to consider reductions in fruit quantity and quality, as some diseases may notrender produce unsalable yet still reduce product value. Postharvest diseases affect a widevariety of crops particularly in developing countries which lack sophisticated postharveststorage facilities. Infection by fungi and bacteria may occur during the growing season, atharvest time, during handling, storage, transport and marketing, or even after purchase bythe consumer. It is also important to take into account costs such as harvesting, packagingand transport when determining the value of produce lost as a result of postharvest wastage.Aside from direct economic considerations, diseased produce poses a potentialhealth risk. A number of fungal genera such as Penicillium, Alternaria andFusarium are known to produce mycotoxins under certain conditions. Generallyspeaking, the greatest risk of mycotoxin contamination occurs when diseasedproduce is used in the production of processed food or animal feed.Losses due to postharvest disease are affected by a great number of factorsincluding:

1. Commodity type2. Cultivar susceptibility to postharvest disease3. Postharvest environment (temperature, relative humidity, atmosphere

composition, etc.)

4. Produce maturity and ripeness stage5. Treatments used for disease control6. Produce handling methods7. Postharvest hygiene.

Virtually all postharvest diseases of fruit are caused by fungi and bacteria. Ingeneral, however, viruses are not an important cause of postharvest disease. The so-called 'quiescent' or 'latent' infections are those where the pathogen initiates

infection of the host at some point in time (usually before harvest), but then enters aperiod of inactivity or dormancy until the physiological status of the host tissuechanges in such a way that infection can proceed. Examples of postharvest diseasesarising from quiescent infections include anthracnose of various tropical fruitcaused by Colletotrichum spp. and grey mould of strawberry caused by Botrytiscinerea. The other major groups of postharvest diseases are those which arise frominfections initiated during and after harvest.

Postharvest diseases of fruit crops: Fruit crops are attacked by a wide range ofmicroorganisms in the postharvest phase. Actual disease only occurs when the attackingpathogen starts to actively grow in the host. Diseases are loosely classified according totheir signs and symptoms. Signs are visible growths of the causal agents, and symptomsthe discernible responses produced by the host. Postharvest diseases are causedprimarily by microscopic bacteria and fungi, with fungi the most important causal agentin fruit crops. Fungi are further subdivided into classes and are described as lower fungi,characterized by the production of sporangia which give rise to numeroussporangiospores, or higher fungi, described as ascomycetes, deuteromycetes, andbasidiomycetes.

Ascomycetes are exemplified by fruiting bodies that release sexual spores when mature.Deuteromycetes, a form of ascomycetes, only release asexual spores. They are morecommon than the sexual ascomycetes stage in postharvest crops. Deuteromycetes arefurther subdivided into hyphomycetes and coelomycetes based on spore and structuralcharacteristics. The agonomycetes contain important soil pathogens that form survivalstructures known as sclerotia that allow them to survive in the absence of the host. Table1 lists many important diseases of fruit crops according to host and causal agents.

Causes of postharvest disease of fruit crops: Correct identification of the pathogencausing postharvest disease is central to the selection of an appropriate disease controlstrategy. Many of the fungi which cause postharvest disease belong to the phylumAscomycota and the associated fungi Anamorphici. In the case of the Ascomycota, theasexual stage of fungus (anamorph) is usually encountered more frequently inpostharvest diseases than the sexual stage of the fungus (teleomorph). Important generaof anamorphic postharvest pathogens include Penicillium, Aspergillus,Geotrichum, Botrytis, Fusarium, Alternaria, Colletotrichum, Dothiorella, Lasiodiplodiaand Phomopsis. In the phylum Oomycota, the genera Phytophthora and Pythium areimportant postharvest pathogens, causing a number of diseases such as brown rot incitrus (Phytophthora citrophthora and P. (parasitica). Rhizopus and Mucor areimportant genera of postharvest pathogens in the phylum Zygornycota. R. stolonifer is acommon wound pathogen of a very wide range of fruit, causing a rapidly spreading

watery soft rot. Genera within the phylum Basidiomycota are generally not importantcausal agents of postharvest disease, although fungi such as Sclerotium rolfsii andRhizoctonia solani.

The major causal agents of bacterial soft rots are various species of Erwinia,Pseudomonas, Bacillus, Lactobacillus and Xanthomonas. Bacterial soft rots are veryimportant postharvest diseases generally of less importance in most fruit (Table 1).

Table 1:- Common postharvest diseases and pathogens of fruit crops.

S. No. Fruit crops Disease Pathogen1 Temperate fruits Blue mould Penicillium spp.2 Pome fruit Gray mould Botrytis cinerea3 Bitter rot Colletrotrichum gloeosporioides4 Alternaria rot Alternaria spp.5 Stone fruit Brown rot Monilia spp.6 Grey mould Botrytis cinerea7 Blue mould Penicillium spp.8 Alternaria rot Alternaria alternata9 Grapes Grey mould Botrytis cinerea

10 Blue mould Penicillium spp.11 Berries Grey mould Botrytis cinerea12 Cladosporium rot Cladosporium spp.13 Blue mould Penicillium spp.14 Subtropical fruit Blue mould Penicillium italicum15 Citrus fruit Green mould Penicillium digitatum16 Black centre rot Alternaria citri17 Stem end rot Phomopsis citri18 Avocado Anthracnose Colletotrichum gloeosporioides,19 Anthracnose Colletotrichum acutatum20 Stem end rot Dothiorella spp.21 Bacterial soft rot Erwinia carotovora22 Tropical fruit Anthracnose Colletrotrichum musae23 Banana Crown rot Fusarium spp.24 Black end Nigrospora spharica25 Ceratocystis fruit rot Thielaviopsis paradoxa26 Mango Anthracnose Colletrotrichum gloeosporioides27 Stem end rot Phomopsis mangifera28 Black mould Aspergillus niger29 Alternaria rot Alternaria alternate30 Grey mould Botrytis cinerea31 Blue mould Penicillium expansum32 Pawpaw (Papaya) Anthracnose Colletrotrichum spp.33 Black rot Phoma caricae papaya34 Phomopsis rot Phomopsis caricae papaya35 Pine apple Water blister Thielaviopsis paradoxa

36 Fruit let core rot Penicillium funiculosum37 Yeasty rot Saccharomyces spp.38 Bacterial brown rot Erwinia ananas

PREHARVEST FACTORS THAT INFLUENCE POSTHARVEST DIESIESES

Weather: Weather affects many factors related to plant diseases, from the amount ofinoculum that overwinters successfully to the amount of pesticide residue that remains onthe crop at harvest. Abundant inoculum and favorable conditions for infection during theseason often result in heavy infection by the time the produce is harvested. For example,conidia of the fungus that causes bull‟s-eye rot are rain dispersed from cankers andinfected bark to fruit especially if rainfall is prolonged near harvest time, causing rotten fruitin cold storage several months later.Physiological condition: Condition of produce at harvest determines how long thecrop can be safely stored. For example, apples are picked slightly immature to ensurethat they can be stored safely for several months. The onset of ripening and senescencein various fruits renders them more susceptible to infection by pathogens. On the otherhand, fruits can be made less prone to decay by management of crop nutrition.Fungicide Sprays: Certain pre-harvest sprays are known to reduce decay in storage.Several studies have been done on the effectiveness of pre-harvest ziram fungicideapplication on pome fruit and show an average reduction in decay of about 25 to 50%with a single spray. Iprodione has been used for several years as a pre-harvest spray 1day before harvest to prevent infection of stone fruit by Monilinia spp. In combinationwith wax and/or oil its decay control spectrum is increased and it will also controlpostharvest fungi such as Rhizopus, and Alternaria. The new class of strobilurinfungicides promises to provide postharvest control of several diseases in fruits. They areespecially effective against fruit scab on apples and should reduce the presence of pinpoint scab in storage.

POSTHARVEST FACTORS THAT INFLUENCE DECAY

Packing Sanitation: It is important to maintain sanitary conditions in all areas whereproduce is packed. Organic matter (culls, extraneous plant parts, soil) can act assubstrates for decay-causing pathogens. For example, in apple and pearpackinghouses, the flumes and dump tank accumulate spores and may act as sources ofcontamination if steps are not taken to destroy or remove them. Chlorine readily killsmicroorganisms suspended in dump tanks and flumes if the amount of availablechlorine is adequate. A level of 50 to 100 ppm of active chlorine provides excellentfungicidal activity. Chlorine measured as hypochlorous acid can be obtained by addingchlorine gas, sodium hypochlorite, or dry calcium hypochlorite. Although chlorineeffectively kills spores in water it does not protect wounded tissue against subsequentinfection from spores lodged in wounds. Organic matter in the water inactivates

chlorine, and levels of chlorine must be constantly monitored. Recently, in preciselycontrolled tests in water or as foam, chlorine dioxide was found to be effective againstcommon postharvest decay fungi on fruit packinghouse surfaces.

Postharvest Treatments: Products used for postharvest decay control should only beused after the following critical points are considered:

Type of pathogen involved in the decay.1. Location of the pathogen in the produce.2. Best time for application of the treatment.

3. Maturity of the host.4. Environment during storage, transportation and marketing of produce. Specific

materials are selected based on these conditions and fall into either chemical orbiological categories listed below.

Fungicide treatments: Several fungicides are presently used as postharvest treatmentsfor control of a wide spectrum of decay-causing microorganisms. However, whencompared to pre-harvest pest control products the number is very small. For example,intensive and continuous use of fungicides for control of blue and green mold on citrushas led to resistance by the causal pathogens of these diseases. Chemical treatmentsthat are presently used are thiabendazole, dichloran, and imazalil. However,resistance to thiabendazole and imazalil is widespread and their use as effectivematerials is declining. These products include sodium benzoate, the parabens, sorbicacid, propionic acid, SO2, acetic acid, nitrites and nitrates, and antibiotics such as nisin.

Biological control: Postharvest biological control is a relatively new approach andoffers several advantages over conventional biological control.1. Exact environmental conditions can be established and maintained.2. The bio-control agent can be targeted much more efficiently.3. Expensive control procedures are cost-effective on harvested food.

Several biological control agents have been developed in recent years, and a fewhave actually been registered for use on fruit crops. The first biological controlagent developed for postharvest use was a strain of Bacillus subtitles. It controlledpeach brown rot, but when a commercial formulation of the bacterium was made,adequate disease control was not obtained.

Irradiation: Although ultraviolet light has a lethal effect on bacteria and fungi thatare exposed to the direct rays, there is no evidence that it reduces decay of

packaged fruits. More recently, low doses of ultraviolet light irradiation (254 nmUV-C) reduced postharvest brown rot of peaches. In this case, the low doseultraviolet light treatments had two effects on brown rot development; reduction inthe inoculum of the pathogen and induced resistance in the host. Gamma radiationhas been studied for controlling decay, disinfestation, and extending the storage andshelf-life of fresh fruits. A dose of 2 5 0 Gy has an adverse effect ongrapefruits increasing skin pitting, scald, and decay. Low doses of 150 for fruit fliesand 250 gray (Gy) for codling moth are acceptable quarantine procedures. Gammairradiation may be used more in the future once methyl bromide is no longeravailable to control insect infestation in stored products. All uses of methyl bromideare being phased out to avoid any further damage to the protective layer of ozonesurrounding the earth.

Temperature and relative humidity: Proper management of temperature is so criticalto postharvest disease control that all other treatments can be considered as

supplements to refrigeration. Fruit rot fungi generally grow optimally at 20 to 250C

(68 to 770F) and can be conveniently divided into those with a growth minimum of

5 to 100C (41 to 500F) or -6 to 00C (21.2 to 320F). Fungi with a minimum growth

temperature below -20C (28.40F) cannot be completely stopped by refrigerationwithout freezing fruit (Shine, et al. 2007). High temperature may be used to controlpostharvest decay on crops that are injured by low temperatures such as mango

and papaya. Heating of pears at temperatures from 21 to 380C (69.8 to 100.40F) for1 to 7 days reduced postharvest decay. Decay in “Golden Delicious‟ appleswas reduced by exposure to 380C (100.40F) for 4 days and virtually eliminatedwhen treated after inoculation.

7. LECTURE NOTES

Harvesting and Field Handling

In general, these are the three different harvesting methods that take place when harvesting fruitsand vegetables:

1. Hand Harvesting2. Harvesting with Hand Tools3. Harvesting with Machinery

I. Hand harvesting:

It predominates for the fresh market and extended harvest period (due to climate, there isaccelerated ripening and a need to harvest the crop quickly) particularly the produce which ismore susceptible to physical injury and soft fruit like grapes/litchis/jamun and strawberry andothers berries which are borne on low growing plants.

Benefits of hand harvesting

Hand harvesting is less expensive

Less damage and harvest rate (times) can be increased,The main benefit of hand harvesting over mechanized harvesting is that humans are able toselect the produce at its correct stage of ripening and handle it carefully. The result is ahigher quality product with minimum damage. Examples,

• Breaking off – twisting off pineapple, papaya, tomato

• Cutting – snipping off mandarins and table grapes with secateurs and apple, roses etc

Harvesting methods is also use full reducing incidence of fungal infection inpapaya/grapefruit.-When fruit are cut from the tree using clipper shows less infection thenthe harvesting by twisting and pulling .

But harvesting small fruits and from thorny plants are major obstacle (disadvantage).

II. Harvesting with Hand Tools

This harvesting method is typically carried out when harvesting tree fruit, where some sort ofclipper (usually specialized for the type of produce being harvested) is used to remove thefruit from the tree, and then the fruit is placed into harvesting containers.

Tools and containers for harvesting

Tools –

Depending on the type of fruit or vegetable, several devices are employed to harvestproduce. Commonly used tools for fruit and vegetable harvesting are secateurs or knives, andhand held or pole mounted picking shears.

When fruits or vegetables are difficult to catch, such as mangoes or avocados, a cushioningmaterial is placed around the tree to prevent damage to the fruit when dropping from hightrees.

Containers –

Harvesting containers must be easy to handle for workers for picking/cutting produce inthe field. Many crops are harvested into bags. Harvesting bags with shoulder or waist slings (asthey are easy to carry and leave both hands free) can be used for fruits with firm skins, likemango, citrus, avocados etc. The contents of the bag are emptied through the bottom into a fieldcontainer without tipping the bag. These containers are made from a variety of materials such aspaper, polyethylene film, sisal, hessian or woven polyethylene and are relatively cheap but givelittle protection to the crop against handling and transport damage. Sacks are commonly used forcrops such as potatoes, onions, cassava, and pumpkins.

Plastic buckets - are suitable containers for harvesting fruits that are easily crushed, such astomato. These containers should be smooth without any sharp edges that could damage theproduce.

Use of bulk bins (commercial growers) - with a capacity of 250-500 kg, in which crops such asapples and cabbages are placed, and sent to large-scale packinghouses for selection, grading andpacking and packing other types of field harvest containers include baskets, carts, and plasticcrate. For high risk products, woven baskets and sacks are not recommended because of the riskof contamination. Ex. Strawberry.

Field Handling of fruits and vegetables

Field handling or post harvest handling considered following points

(i) Washing and cleaning: Washing is used not only to remove field soil and surfacemicro-organism but also to remove fungicides, insecticide and other pesticides fromvegetables. Washing water contains detergents or other sanitizers that can

essentially completely remove these residues.Most produce receives variouschemical treatments such as spraying of insecticides and pesticides in the field. Mostof these chemicals are poisonous to humans, even in small concentrations.Therefore, all traces of chemicals must be removed from produce before packing. Asillustrated in Figure 2.7, the fruit or vegetable passes over rotary brushes where it isrotated and transported to the washing machine and exposed to the cleaningprocess from all sides:Figure: Typical produce washing machine.

From the washing machine, the fruit passes onto a set of rotary sponge rollers (similar tothe rotary brushes). The rotary sponges remove most of the water on the fruit as it isrotated and transported through the sponger.

(ii) Disinfection: After washing fruits and vegetables, disinfectant agents are added to thesoaking tank to avoid propagation of diseases among consecutive batches of produce. In asoaking tank, a typical solution for citrus fruit includes a mixture of various chemicals atspecific concentration, pH, and temperature, as well as detergents and water softeners.Sodium-ortho-phenyl-phenate (SOPP) is an effective citrus disinfectant, but requiresprecise control of conditions in the tank. Concentrations must be kept between 0.05 and0.15%, with pH at 11.8 and temperature in the range of 43-48°C. Recommended soakingtime is 3-5 minutes.

(iii) Sorting and Grading : This step covers two separate operations to remove of non-standard vegetables and possible foreign bodies remaining after washing and qualitygrading based on variety, dimensional organoleptic and maturity stage criterion.

(iv) Artificial waxing: Artificial wax is applied to produce to replace the natural wax lostduring washing of fruits or vegetables. This adds a bright sheen to the product. Thefunction of artificial waxing of produce is summarized below:

Provides a protective coating over entire surface. Seals small cracks and dents in the rind or skin. Seals off stem scars or base of petiole. Reduces moisture loss. Permits natural respiration. Extends shelf life. Enhances sales appeal

(v) Precooling : Rapid cooling as soon as possible after harvest is essential to themaintenance of optimum quality. The first consideration at harvest is removal of theproduce from direct sunlight, and secondly, to precool as quickly as possible.

Precooling Methods

(i) Room Cooling: Exposure of produce to cold air in an enclosed space is the simplest andmost common cooling method. Cold air normally is discharged horizontally near theceiling so as to enable it to return through produce stacked on the floor. The precookingroom may also be the storage room. This results in less handling of the product. Heat isremoved slowly so the peak demand for refrigeration is less than with more rapid coolingsystems. Since cooling is slow, shipments may be delayed, or in some cases the productmay be shipped without adequate precooking. Certain commodities, such as snap beans,may deteriorate before cooling is accomplished. These problems may be minimized byensuring that containers are stacked to facilitate good air circulation. Fans must bepowerful enough to move the air at a velocity of 2 to 4 miles per hour among thecontainers, which should be vented adequately.

(ii) Forced-Air Cooling: Forced-air cooling or pressure cooling is accomplished through theuse of fans and strategically placed barriers so that cold air is forced to pass through thecontainers of produce. This method usually takes from 1/4th to 1/10th the time requiredto cool produce by passive room cooling, but takes two or three times longer than hydroor vacuum cooling. Room coolers are relatively easy to adapt to forced-air. However, therefrigeration capacity of the room may need to be increased to compensate for the rapidremoval of heat from the produce. Commodities should not be left on the cooler longerthan the time required to reach about 1/8th of their initial temperature because water lossfrom the product is increased. The importance of humidity control is discussed in a latersection. Cooling schedules should be calculated to avoid this problem.

(iii) Icing: The use of ice for cooling, either by package icing or by bulk application to thetop of a load, is one of the oldest cooling methods. The use of slurries and mechanizationof the process have made this a popular method for some commodities like broccoli.

Cartons must be able to withstand free water. Once iced, they should be placed in arefrigerated storage unit or transit vehicle. As the ice melts, high relative humidity ispresent surrounding the produce. A rule of thumb for the cooling capacity of ice is that, tocool a produce from 95F to 35F, the weight of ice needed is equivalent to 38% of theproduce weight. Most packed cartons have enough free space to include this amount ofice. It is essential that only high quality ice made from potable water be used.

(iv) Hydro cooling: Hydro cooling is one of the most efficient of all methods forprecooking. Produce is drenched with cold water, either on a moving conveyor or in astationary setting. In some cases, commodities may be forced through a tank of coldwater. Hydro cooling is an excellent method for bulky items such as sweet corn, peaches,or cantaloupes. Good water sanitation practices must be observed and once cooled, theproduce should be kept cold. The cold water must come in direct contact with theproduct, so it is essential the containers be designed and filled in such a way that thewater does not simply channel through without making contact. Studies have shown thatsome commercial hydrocoolers are not adequately insulated and as much as half of theenergy for refrigeration is wasted.

(v) Vacuum Cooling: Commodities may be enclosed in a sealed container from which airand water vapor are rapidly pumped out. As the air pressure is reduced, the boiling pointof water is lowered, so the product is cooled by surface water evaporation. Vacuumcooling works best with products that have a high surface to volume ratio, such as lettuceor leafy greens. The method is effective on produce that is already packaged providingthere is a means for water vapor to escape. Moisture loss from the commodity isgenerally within the range of 1.5 to 5.0%. Generally, about 1% of the weight is lost foreach 10oF the product is cooled. This can be reduced by wetting the product beforecooling. Vacuum chambers vary in size from very large, about rail car size, to smallerportable units that may be taken to the field.

(vi) Evaporative Cooling :The use of wet pads and fans to cool the air in greenhouses is acommon practice. This can be adapted to the cooling of horticultural commodities,however, the benefits are few compared to other methods of cooling. With this methodair temperature can be reduced to near the wet bulb temperature, but not below it.Therefore, most items cannot be cooled adequately by this method. It does offer thebenefit of surrounding the produce with air of very high relative humidity, which helps toreduce shrinkage. Roadside markets, or other outlets in which long term storage is notneeded, may be the most practical application for an evaporative cooler.

8. LECTURE NOTES

Storage

Fruit and vegetable crops are seasonal in nature and have a relativelyshort harvesting season and they are also highly perishable. Hence, proper storage of theseproduce using appropriate methods would prolong their availability. Storage of fresh producewill also be helpful in checking market glut, providing wide selection of fruits and vegetablesto the consumer through most part of the year i.e. especially during the off season. Storagehelps in orderly marketing and increases profit to the producers/farmers. Storage of freshproduce is done to maintain freshness, quality, reduce the spoilage and extend their usefulness.One of the reasons for the huge post harvest losses of horticultural produce is lack of properstorage facilities. The basic principle of storage is to reduce the rate of physiological processeslike respiration, transpiration, ripening and other biochemical changes. Proper storage alsoaims at controlling disease infection and preserving the commodity in its best quality forconsumers. The management of temperature and relative humidity are the most importantfactors determining storage life of horticultural produce.

Principles of storage:

1. Control of respiration rate:

Fruits and vegetables are living commodities means the process of respirationand transpiration continue even after harvesting. Respiration is a breakdown process.The heat generated during respiration, usually know as respiratory heat /heat ofrespiration, accumulates in the centre of the storage should be separated for prolongstorage of fruits and vegetables. Proper ventilation will help in removing this heatthereby reducing the respiration rate. Reducing respiration rate will also help indelaying the ripening process in some fruits and vegetables thereby extendingthe storage life. Cold storage, atmospheric modification, low pressure storage are themethods used based on this principle.

2. Control of transpiration rate:

Fresh produce continues to lose water even after harvest resulting in wilting orshriveling of produce. A 5% loss of moisture make the produce unattractive formarketing. Relative humidity and temperature are the important factors thatinfluence the loss of moisture from fresh produce. Water loss will also be high with

increase in storage temperature. Fresh produce transpire more at high temperaturesand low humidity. Hence, this process can be controlled by storing the produce atlow temperatures and high relative humidity.

3. Control of sprouting and rooting:

Some root and tuber type vegetables after harvest enter into a resting phenomenonknown as Dormancy. During this period, sprouting and rooting of these crops doesnot occur. However, under favourable conditions these crops re-grow resulting insprouting and rooting. Consumers do not prefer the sprouted or rooted vegetables forbuying. Sprouting also makes the produce to lose moisture quickly, shrivel andbecome prone to microbial infection. Hence, prolonging the dormant period bycreating unfavorable conditions is the principle for extending the storage life of thistype of produce.

4. Control of spoilage:

Fresh produce have high moisture and readily available nutrient and thereforereadily attacked by microorganisms. Favourable conditions like warm temperatureand high humid condition in the storage room enhance the growth of these micro-organisms and increase the spoilage. Hence, storage methods should aim at retardingor control of the growth of these spoilage causing micro-organisms.

Objective of Storage:

Slow down biological activity Reduce product drying and moisture loss Reduce pathogenic infection Avoid physiological disorders Reduce physical damage Avoid glut and distress sale in the market, thus prolonging the market period. In long-term storage, making the food available in off-season.

Factors affecting storage:1. Storage life of fresh horticultural produce is affected by many factors like2. Pre harvest factors3. Maturity at harvest4. Harvesting and handling practices5. Pre-storage treatments6. Temperature and humidity in storage room

Temperature and relative humidity are the most important among the above factors.Fresh horticultural produce continue to respire after harvest and temperature is able toregulate this physiological activity. Higher the temperature, faster the, these physiologicaland biochemical processes leading to early senescence.

Storage life of horticultural produce may be extended by temperature control, chemicaltreatments, atmosphere modification, mainly by regulating the physiological processes andcontrolling the post harvest diseases and pests. Low temperature storage is the only knowneconomical method for long term storage and quality maintenance of horticultural produce.Lowering the temperature to the lowest safe handling temperature is of paramountimportance for enhancing the shelf life, reducing the losses and maintaining higherquality during marketing.

Methods of storage:

1. Zero Energy Cool Chamber2. Cold Storage3. Hypobaric Storage4. Controlled Atmosphere Storage5. Modified Atmosphere Storage

Zero Energy Cool Chamber:

An on-farm, low cost, environmentally friendly cool chamber, designated a Zero EnergyCool Chamber was developed in India, from locally available material. Temperatures within thischamber, which works on the basis of evaporative cooling principles, are reduced by as much as17–18°C, with a relative humidity in excess of 90% during peak summer periods. This chamberincreases shelf life and reduces wastage of bananas, mangoes, oranges, limes, grapes, tomatoesand potatoes in different situations in India.

It is based on the principle of direct evaporative cooling. It does not require anyelectricity or fuel to operate. The materials required to make this chamber are cheap andavailable easily.

Construction

Select an upland having a nearby source of water supply Make floor with brick 165 cm x 115 cm Erect the double wall to a height of 67.5 cm leaving a cavity of 7.5 cm. Drench the chamber with water Soak the fine river bed sand with water

Fill the 7.5 cm cavity between the double wall with this wet sand Make a frame of top cover with bamboo (165 cm x 115 cm) frame and sirki, straw or dry

grass etc. Make attach/ shed over the chamber in order to protect it from direct sun or rain.

Operation

Keep the sand, bricks and top cover of the chamber wet with water. Water twice daily in order to achieve desired temperature and relative humidity or fix a

drip system with plastic pipes and micro tubes connected to an overhead water source. Store the fruits and vegetables in this chamber by keeping in perforated plastic crates Cover these crates with a thin polyethylene sheet The cool chamber should be reinstalled once in 3 years with new bricks utilizing the old

bricks for other purposes.

Precautions

Try to site in a place where breezes blow Build in an elevated place to avoid water logging Use clean, unbroken bricks with good porosity Sand should be clean and free of organic matters, clay etc. Keep the bricks and sand saturated with water Roof over to prevent direct exposure to sun Use plastic crates for storage; avoid bamboo baskets, wooden/fiber board/boxes, gunny

bags etc. Prevent water drops coming in contact with stored material Keep the chamber clean and disinfect the chamber periodically with permitted

insecticide/ fungicide/ chemical, to protect from fungus, insect/ pests, reptiles etc.

Areas of Application

Short term storage of fresh vegetables, fruits and flowers Growing of white button mushroom Ripening of tomato and banana Plant propagation Storage of processed fruit products

Advantages

Avoid distress sale of fresh fruits, vegetables and flowers. Better marketability of fresh horticultural produce than ambient Retain nutritive value Environment friendly storage system with no pollution

Cold Storage:

Low temperature storage is the best known, effective and most widely used method forextending the storage life and long terms storage of fruits and vegetables. In post harvesttechnology temperature management is the most important aspect to be looked after to maintainquality, reduce losses and extend the storage life of these perishable commodities.

Cold storage is the one widely practiced method for bulk handling of the perishablesbetween production and marketing or processing. Cold storage is a system with thermalinsulation and refrigeration in which perishables commodities can be stored for a set period oftime under controlled conditions of temperature and humidity. It is one of the methods ofreserving perishable commodities in fresh and wholesome state for a longer period by controllingtemperature and humidity with in the storage system. Maintaining adequately low temperature iscritical, as otherwise it will cause chilling injury to the produce. Also, relative humidity of thestoreroom should be kept as high as 80-90% for most of the perishables, below (or) above whichhis detrimental effect on the keeping quality of the produce.

Need of cold storage:

For preservationFor maintaining nutritional qualityTo increase storage lifeTo ensure availability of the produce throughout the year for direct consumption as

well as processingTo reduce losses due to wastageTo preserve the seasonal produce and selling during off season to fetch higher returns

Factors involved for effective cold storage of the produce:

Product quality: Fresh horticultural produce intended for storage should be freefrom physical damage, of optimum maturity and free from infections.

Temperature: Low temperature storage is recommended for perishables as itretards respiration and metabolic activity, aging due to ripening, softening andtextural and colour changes, moisture loss, spoilage due to diseases andundesirable growth (sprouting/ cooling). Maintenance of uniform temperatureconstantly, continuously and also adoption of optimum low temperature for eachspecific produce are very essential.

Relative Humidity: The relative humidity of the air in storage rooms directlyaffects the keeping quality of the produce held in them. If it is too low, wilting orshrivelling is likely to occur, if it is too high, it may favour the development ofdecay. An RH of 85-90% is recommended for most perishables.

Air circulation and package spacing: Air must be circulated to keep acold storage room at an even temperature throughout the storage. This is requiredto remove respiratory heat. Entry of outside air and proper spacing of containerson pellets are also important.

Respiration rates, heat evolution and refrigeration: When the storage of freshproduce is considered, it should be remembered that these commodities are aliveand carry on all activities of living tissues, the most important being respiration.During this process, energy is released in the form of heat which varies with thecommodity and the temperature. This `vital heat' expressed in BTU (Britishthermal units) is of paramount importance in calculating the refrigeration load ofthe commodity.

Weight loss in storage: Loss of water from harvested horticultural crops is amajor cause of deterioration in storage. Some loss can be tolerated but losses greatenough to cause wilting or shrivelling must be avoided. Under good handlingconditions with recommended humidity and temperature, moisture loss can beheld under control.

Sanitation and Air purification: Good air circulation alone is of considerablevalue in minimizing surface moulds. Accumulation of odours and volatiles maycontribute to off flavours and hasten deterioration.

Temperature management: Refrigeration (Low temperature and humidity)requirements vary with different kinds of fresh produce and the maturity stages.For most of the fresh fruits and vegetables (except onion, garlic) the relativehumidity in cold storage should be kept in the range of 85 to 95%. TemperatureManagement involving storage at optimum temperature requirement of eachproduce (as shown in the tables) is very essential to maintain quality andextend storage life. Chilling injury, to which the tropical fruits and vegetables are

susceptible/sensitive, is a major problem, if they are stored at lower than optimumtemperature.

Different types of cold storage:

Based on the purpose the present day cold stores are classified into following groups:

1. Bulk cold stores: Generally, for storage of a single commodity which mostlyoperates on seasonal basis E.g.: stores for potatoes, chilies, apples etc.

2. Multipurpose cold stores: It is designed for storage of variety of commodities,which operate practically, throughout the year.

3. Small cold stores: It is designed with pre cooling facilities. For fresh fruits andvegetables, mainly for export oriented items like grapes etc.

4. Frozen food stores: It is designed for with (or) without processing and freezingfacilities for fish, meat, poultry, dairy products and processed fruits andvegetables.

5. Mini units /walk in cold stores: It is located at distribution center etc.6. Controlled atmosphere (CA) stores: It is mainly designed for certain fruits and

vegetables.

General arrangements and considerations:

If produce is to be stored, it is important to begin with a high quality product. Theproduce must not contain damaged or diseased units, and containers must be wellventilated and strong enough to withstand stacking. In general proper storage practicesinclude temperature control, relative humidity control, air circulation and maintenance ofspace between containers for adequate ventilation, and avoiding incompatible productmixes. Commodities stored together should be capable of tolerating the sametemperature, relative humidity and level of ethylene in the storage environment. Highethylene producers (such as ripe bananas and apples) can stimulate physiological changesin ethylene sensitive commodities (such as lettuce, cucumbers, carrots, potatoes, sweetpotatoes) leading to often undesirable color, flavor and texture changes.

The general features of a cold store operational programme (products, chilling andchilled storage and freezing) include total capacity, number and size of rooms,refrigeration system, storage and handling equipment and access facilities. The relativepositioning of the different parts will condition the refrigeration system chosen. The siteof the cold chambers should be decided once the sizes are known, but as a general rulethey should be in the shade of direct sunlight. The land area must be large enough for thestore, its annexes and areas for traffic, parking and possible future enlargement. A landarea about six to ten times the area of the covered surface will suffice.

Low Pressure Storage / Hypobaric Storage

Hypobaric storage is a form of controlled atmosphere storage in which theproduce is stored in a partial vacuum. The vacuum chamber is vented continuouslywith water saturated air to maintain oxygen levels and to minimize water loss.Ripening of fruit is retarded by hypobaric storage, due to the reduction in the partialpressure of oxygen and for some fruits also to the reduction in the ethylene levels. Areduction in pressure of air to 10 kilopascals (0.1 atmosphere) is equivalent toreducing the oxygen concentration to about 2 per cent at normal atmospheric pressure.Hypobaric stores are expensive to construct because of the low internal pressuresrequired, and this high cost of application appears to limit hypobaric storage to highvalue produce such as cut flowers. Secondly control of gases during the storage cannotbe manipulated.

Fruits can be stored under low pressure of 0.2 – 0.5 atmospheric pressure andtemperature of 15 - 240C under airtight chamber. Pressure is reduced by sucking air andcreating vacuum.

Control Atmosphere/Modified Atmosphere Storage:The term imply, the addition or removal of gases resulting in an atmospheric

composition different from that of normal air. Thus the levels of carbon dioxide,oxygen, nitrogen, ethylene, and metabolic volatiles in the atmosphere may bemanipulated. Controlled atmosphere storage generally refers to keeping produce atdecreased oxygen and increased carbon dioxide concentrations and at suitable range oftemperature and RH. Systems where atmospheric control is accurately controlled aregenerally called CA storage and where degree of control “less accurately” monitoredare called MA (modified atmosphere) storage. In MAP (modified atmosphericpackaging) produce is enclosed in polymeric films and is allowed to generate its ownatmsophere (passive MAP) or air of known composition is flushed into the bag(active MAP) and depending upon gas / vapour transmission characteristics of thefilm on appropriate atmosphere develops in the package to prolong shelf life. MAP isideally combined with temperature control for maximum benefit

Control Atmosphere Storage:

The storage of fruits and vegetables in CA Storage is one of the most advancedmethods of storage. It was first suggested by W.R. Philips of Canada.From the construction point of view, controlled atmosphere facilities are similar torefrigeration facilities. However, they should be airtight to allow creation of anatmosphere different from normal. The Oxygen consumption and its replacement bycarbon dioxide by respiration, create the atmosphere. When the appropriatecombination has been reached, a limited intake of oxygen is required to satisfy the

reduced rate of respiration. Accumulation of carbon dioxide is removed by means ofdifferent methods. In CA storage, oxygen is reduced and CO2 is increased andripening and respiration rates are slowed down.

Essential features of CA Storage

1. Mechanical refrigeration is used to maintain temperature of -1 to 3°C.The CA storage room is constructed gas tight.

2. Reduction on O2 - Nitrogen gas is introduced into the storage by cylinder toreduce the oxygen level after room is filled and sealed. CO2 is addedinto storage from CO2 gas cylinder.

3. Excess CO2 is removed by dry hydrated lime, Ethanolamine, Aluminium calciumsilicate, Activated carbon, Magnesium oxide, activated carbon are other CO2

scrubbers.4. Atmospheric composition is crop specific. However, as a general rule the most

common combinations are 2-5% oxygen and 3-10% carbon dioxide.5. The storage room atmosphere samples are taken daily for CO2 and O2 monitoring.

Benefits of CA storage: Slow down respiration and ethylene production rates, softening and retard

senescence of horticultural produce.

Reduce fruit sensitivity to ethylene action Alleviate certain physiological disorders such as chilling injury of

various commodities, russet spotting in lettuce, and some storage disordersincluding, scald of apples.

Harmful effects of CA storage: Initiation or aggravation of certain physiological disorders can occur, such

as blackheart in potatoes, brown stain on lettuce, and brown heart in apples andpears.

Irregular ripening of fruits, such as banana, mango, pear and tomato, can resultfrom exposure to O2 levels below 2% or CO2 levels above 5% for more than 2 to 4

weeks. Off- flavors and off-odours at very low O2 or very high CO2 concentration

may develop as a result of anaerobic respiration and fermentative metabolism.

Modified atmosphere storage:

Modified atmosphere packaging, also known as “maintain and preserve”technology is employed to maintain and preserve the quality of fruit for shipping andpacking. Modifying the environment around fresh produce, can alter its rate ofrespiration and metabolism, and increase its commercial storage life. Modifiedatmospheres can be generated by either active or passive systems. In the passivesystem, respiring fruit, over time, self-generate an atmo- sphere of elevated carbondioxide and reduced oxygen, while in the active system, desired end-pointconcentrations of oxygen and carbon dioxide are established by flushing the fruit witha desired mix of gases. Development of a MAP system must integrated considerationfor the type, thickness and method of fabrication of the film, package size,temperature, relative humidity, duration of storage, type, quantity and physiologicalstage of fruit and tolerance of fruit to the various gases.

The rate of respiration and metabolism doubles for every 10°C rise intemperature. Respiration can be therefore reduced by decreasing the temperature, O2level and/or increasing the CO2 level in the storage atmosphere. Both O2 and CO2levels exert independent effects on respiration. The net effect may be additive orsynergistic. When O2 concentration is reduced below 10%, respiration rate isdecreased. However, when O2 concentration falls below 2%, anaerobic respirationmay set in, thereby leading to the accumulation of ethanol and acetaldehyde.The desirable effect of MA on plant tissues is also attributed to lower pH, due todissolution of CO2 in tissues. Ethylene action and biosynthesis are also effectedbesides water loss and chilling injury

MAP is very effective in retaining freshness, and for extending the shelf life offresh fruit and vegetables. MAP is also ideal for the marketing of minimally processedproduce, such as mixed salads, fruit salads and fresh cut produce. This type of package isdesigned to exactly match the handling conditions and respiration rates of specificallypackaged produce, by manipulating O2 and CO2 levels in the packages, so as to:

• Maintain the green color of leafy vegetables;

• Reduce loss due to the production of respiratory heat by produce;

• Maintain the natural fresh taste of produce;

• Extend the shelf life;

• Delay ripening.

In some instances, MAP films are impregnated with minerals, in order to absorb andremove ethylene produced in the storage environment around the bagged produce.Impregnated MAP films are particularly suitable for transporting bulk fresh fruit and

vegetables to distant markets or between farmers and consumers at supermarkets andretail outlets. The produce must, however, be properly handled and packaged prior totransport.

Environmental factors affecting MA storage

a. Temperature and relative humidity

Ambient temperatures of the surrounding atmosphere affect the commoditytemperature. Temperature changes also affect the permeability of the film,which increases with increase in temperature. CO2 permeability responds morethan O2 permeability. Relative humidity has little effect on permeability ofmost film packages. Most common films are good barriers to moisture andvapour because they maintain high internal humidity even in dry, ambientconditions.

b. Light

Green vegetables consume large amount of CO2 and reduce O2 throughphotosynthesis and would antagonize the process of respiration which aids inmaintenance of specified MA within the package. Greening of potatoes cancause loss in quality unless light is excluded. Hence, opaque packages shouldbe used for such commodities.

c. Sanitation Factors

The high humidity maintained within MA packages may enhance the growthof plant pathogens. So care must be taken to ensure proper sanitation and toavoid conditions favourable to growth and reproduction of such microorganisms. Fungicidal treatment of packaged vegetables is thus very important.

Advantages of MAP:

• Extends shelf life• Prevents dehydration• Retains green color and prevents yellowing• Preserves fresh taste and aroma• Delays ripening• Prevents fungal and bacterial growth• Increases the sale of fresh produce.

9. LECTURE NOTES

Value Addition-Concept and Importance of Fruits and Vegetables Preservation

Fruits and vegetables provide an abundant and inexpensive source of energy, nutrients,vitamins, minerals, fiber etc. Their nutritional value is highest when they are fresh, but it is notalways possible to consume them immediately. During the harvest season, fresh produce isavailable in abundance, but at other times it is scarce. Moreover, most fruits and vegetables areonly edible for a very short time, unless they are promptly and properly preserved.

India’s diverse climate ensures availability of all varieties of fresh fruits and vegetables.It ranks second after china. Post-harvest losses of fruits and vegetables are more serious indeveloping countries than those in well-developed countries. The total losses from harvest to theconsumer point are as high as 30-40%, which is worth thousands of crores of rupees. About 10-15% of fresh fruits and vegetables shrivel and stale, lowering their market value and consumeracceptability.

Processing and value addition of fruit and vegetable crops mainly helps to reduce the postharvest losses, increase the nutritional security and also for utilization of waste in better way.

Value is added by changing their form, colour and other such methods to increase the shelflife of perishables. Fruit and vegetable crops play an important role in meeting the nutritionalrequirement with maximum value addition and foreign exchange earnings.

Methods of processing of fruits and vegetables into value added products:

• Preservation by heat treatment.• Asceptic packaging.• Preservation of by removal of heat.• Quick freezing.• Preservation by removal of moisture.• Preservation by addition of chemicals.• Minimal processing.

Value added products from fruits

Juice, RTS, Nectar, Squash, cordial, jam, preserve, toffee, Amchur, pickle, chutney, cannedproduct, fruit powder, concentrate, jelly, cheese, toffee, vinegar, syrup, candy, wine, driedproduct, marmalade, cider, pickle.

Fruit Beverages:

Fruit beverages are easily digestible, highly refreshing, thirst quenching, appetizing andnutritionally far superior to many synthetic and aerated drinks. They can be classified intounfermented and fermented beverages.

Unfermented beverages

They include natural and sweetened juices, RTS, nectar, cordial, squash, crush, syrup,fruit juice concentrate and fruit juice powder. Barley waters and carbonated beverages are alsoincluded in this group.

Fermented beverages

Fruit juices which have undergone alcoholic fermentation by yeasts include wine,champaigne, port, sherry, tokay, muscat, perry, orange wine, berry wine, nira and cider.

Intermediate Moisture Foods:

Jam

Apple, pear, sapota (chiku), peach, papaya, karonda, carrot, plum, straw-berry, raspberry,mango, tomato, grapes and muskmelon are used for preparation of jams. It can be prepared fromone kind of fruit or from two or more kinds.

Jelly

Guava, sour apple, plum, karonda, wood apple, loquat, papaya and goose-berry aregenerally used for preparation of jelly. Apricot, pineapple, strawberry, raspberry, etc. can be usedbut only after addition of pectin powder, because these fruits have low pectin content.

Marmalade

The term is generally used for products made from citrus fruits like oranges and lemonsin which shredded peel is used as the suspended material. Citrus marmalades are classified into(i) jelly marmalade, and (ii) jam marmalade.

Candy:

The most suitable fruits for candying are aonla, karonda, pineapple, cherry, papaya,apple, peach, and peels of orange, lemon, grapefruit and citron, ginger, etc.

Glazed candy

Covering of candied fruits / vegetables with a thin transparent coating of sugar, whichimparts them a glossy appearance, is known as glazing.

Crystallized candy

Candied fruits/ vegetables when covered or coated with crystals of sugar, either by rollingin finely powdered sugar or by allowing sugar crystals to deposit on them from a dense syrup arecalled crystallized fruits.

Preserve:

A mature fruit / vegetable or its pieces impregnated with heavy sugar syrup till itbecomes tender and transparent is known as a preserve. Aonla, bael, apple, pear, mango, cherry,karonda, strawberry, pineapple, papaya, etc. can be used for making preserves.

Dehydration of fruits:

Dehydration means the process of removal of moisture by the application of artificial heatunder controlled conditions of temperature, humidity and air low. In this process a single layer offruits, whole or cut into pieces or slices are spread on trays which are placed inside thedehydrator. The initial temperature of the dehydrator is usually 43°C which is graduallyincreased to 66-71°C for fruits.

Pickles:

The preservation of food in common salt or in vinegar is known as pickling. It is one of themost ancient methods of preserving fruits and vegetables.

Value addition in vegetable crops:

Vegetables are classified as green leafy vegetables, roots and tubers and others. Carrotsamong roots and tubers and fenugreek leaves among green leafy vegetables grown in winterseason occupy an important place. These vegetables are rich sources of beta carotene and aregenerally marketed fresh and consumed as raw or cooked vegetables. Due to the seasonalavailability, efforts are made to process the vegetables in large quantity to extend the shelf lifeand to make them available during rest of the year and in the areas, where they are not available.Preservation of vegetables by processing not only involves the inhibition of microbial growth,but also preserves their color, texture, flavor and nutritive value. The vegetables can beprocessed into different forms to extend their shelf life such as powders, grits, flakes, pulp,puree, etc. The vegetables can be dried by hot air drying method for small scale operation or by

conventional tray drier or vacuum drier, and at home level can be processed by sun dryingmethod. These dehydrated forms of vegetables may be eaten as such or may be consumed inseveral forms, without affecting its nutrition and palatability. Vegetable powders such as carrot,tomato and fenugreek leaves powder can be prepared with simple technologies and can beincorporated in traditional food preparations, thereby adding value to the products and attainingfood and nutrition security both.Common vegetables and their value added products:

Tomato:

Tomato are one of the most widely used and versatile vegetable crops, ranking second inimportance to potatoes in many countries. Tomatoes are important both for its large consumptionand richness in health related food components. Tomato is one of the most popular protectivefoods, because of its lycopene content, outstanding nutritive value, antioxidant properties and apowerhouse of medicinal properties. It is a rich source of minerals like calcium, magnesium,phosphorous, iron, sodium, potassium and vitamins especially A and C. Tomatoes are consumedmainly as a raw staple food, as an ingredient in different types of food products and in the formof processed products such as powder, tomato juice, paste, puree, sauce, etc.

Processing of fresh tomatoes can be done to prepare the following value added productslike.

• Tomato pulp• Tomato puree• Tomato paste• Tomato flakes• Canned tomatoes• Tomato sauce and ketchup• Tomato soup and chutney• Tomato powder• Dehydrated tomatoCarrot:

Carrot is another popular root vegetable, which is cultivated and consumed throughoutthe world. It is well known for its nutrient contents viz., carotene and carotenoids, besidesappreciable amount of vitamins and minerals such as ascorbic acid, tocopherol etc. Among rootsand other vegetables, carrot is the best source of carotene, which is a precursor of vitamin A, anessential nutrient for maintaining health.

Different processed products of carrots are:

• Carrot juice• Carrot powder

• Carrot flakes• Canned carrot• Carrot candy• Carrot Halwa• Carrot grits• Carrot soup• Carrot Dalia• Fabricated baby foodsGinger:

Ginger is commonly used as a food additive, and as spice, it is used in food preparation toimpart its characteristic flavor. It has been attributed with antioxidant properties, proteolyticactivity and tenderizing effect. It has been attributed with antioxidant properties which widens itsuse in preservation of meat and meat products. Ginger has been used to treat numerous types ofnausea and vomiting.

The different processed products from ginger include

• Paste• Candy• Preserve• Pickle• Chocolates• Beverages• Powder• Juice• Ice cream• Oleoresin• ginger teaFenugreek Leaves:

Green leafy vegetables are gaining importance, because of being good sources ofvitamins, minerals and dietary fiber. Fenugreek is a popular green leafy vegetable available inplenty, at lower cost during winter season. Blanching treatment is used to preserve the color andnutritional value of GLVs. Fenugreek leaf powder can be obtained by dehydrating fenugreekleaves.

Potato:

Potato is an important and extensively grown horticultural crop in India. Potato is aversatile food, which can be eaten as a staple food, as a complementary vegetable, as a snackitem or processed into several forms, and in any of these roles, it enhances the nutritional qualityof the diets of people. Among the root crops, potatoes top the list and have the distraction of

occupying largest area under any single vegetable in the world. Potatoes are versatile as they canbe consumed in various forms as boiled, fried, baked, roasted, steamed and even in severalpressed forms such as French fries, chips, papad, flakes, dice, cubes, granules, flour, cannedpotatoes etc.

Different processed products of potatoes :

• potato flour• potato grits• potato flakes• potato granules• potato cubesImportance of fruit and vegetable preservation:

Fruits and vegetables are an important supplement to the human diet as they provide theessential minerals, vitamins and fibre required for maintaining health. The varied agro climaticconditions available in our country make it possible for us to produce several types of tropical,subtropical and temperate fruits and vegetables. It has been variously estimated that 20 to 30% ofthe horticultural produce is lost before consumptio because of poor harvesting, handling, storage,transportation and marketing practices. The fruits and vegetables are highly perishablecommodities and the ambient high temperature obtained in the tropical country like ours makesthem more susceptible for rapid development of senescence, decay and rotting. Both rate ofrespiration and transpiration are proportional to temperature, increases and so that the producequickly dries, wilts and spoils unless properly preserved.

Fresh fruits and vegetables should process into various value added products which couldbe preserved for a long time. With increasing urbanization rise in middle class purchasing power,change in food habits there is increasing demands for factory made jams, jellies, fruit beverages,dehydrated foods, pickles etc. in the domestic market. Moreover, there is considerable demandfor some of these products in foreign markets e.g. mangoes both fresh and canned, fruit juices,salted cashew are good foreign exchange earners. The production of fruit and vegetable productsin India are canned, bottled fruits and vegetables, jams, jellies, marmalades, fruit juices, fruitpulps, squashes, crashes, cordials, fruit syrups, fruit nectars, RTS fruit beverages, fruit juiceconcentrates, chutneys, pickles, mango slices in brine preserves, candied and crystallized fruitsand peels, dehydrated fruits and vegetables, frozen fruits and vegetables, tomato products,sauces, soups etc. In India there are lot of small processing industries are functioning. But onlyquantity of 2.0 to 4.0 % of the produce is processed and packaged in contrast with developed anddeveloping countries i.e., 70 to 80%. Thus we can see on enormous scope and potential for theexpansion of fruits and vegetable industries in India in the future. Nearly half of India’sprocessed fruit exports are mango based fruit juice, canned and bottled fruits. Fresh onions andmangoes are the main commodities entering in export trade. The other important fruits exportedare melon, sweet melon, grapes, pomegranate, sapota, custard apple, orange, papaya, pineapple.

10. LECTURE NOTES

(Prepared By: Dr. Aparana Sharma)

Intermediate Moisture Foods

Water plays an important role in all types of food products. Be it raw or cooked, fresh or dried,fruits & vegetables or cereals & pulses, raw or cooked or preserved, veg or non-veg, liquid orsolid; all kinds of food products contain a specific amount of water which is responsible for itstexture, taste, mouthfeel and most important is its shelf-life. However, scientifically speakingmoisture content of the food differs from water activity in the food. On one hand where themoisture content of the food is responsible for the nutritional content and sensory attributes ofthe food, water activity is considered responsible for microbial load or the shelf stability of thefood itself. Free water in fruits and vegetables is the water available for chemical reactions, to actas a transporting medium for various compounds and also to support microbial growth. In boundform, also called the osmotic bonding, it is available with salts, sugars, gums etc.

National Center for Coordination of Research on Food and Nutrition, France during1980’s proposed a comprehensive definition for Intermediate Moisture Foods as, “Food Productsof soft texture, subjected to one or more technological treatments, consumable without furtherpreparation and with a shelf stability of several months, assured without thermal sterilization, norfreezing or refrigeration, but an adequate adjustment of their formulation; composition, pH,additives etc and mainly water activity (aw) which must be between 0.6 and 0.84 (measured at25OC).”Technically speaking, Intermediate Moisture Foods or food products are those which have wateractivity (aw) between 0.75-0.92 (Welti-Chanes et al., 1997). This water activity of these productsis adjusted in the given range by using different preservation methods viz., dehydration, osmoticdehydration and dry infusion. Although different sources report varying water contents forIMF’s, the water content between 20 and 50 per cent may be accepted as the intermediatemoisture level which makes the fruits soft, moist and ready to eat (Cemeroglu, 1986).

Water activity (aw)

Water activity is a thermodynamic property which is defined as the ratio of vapour pressure ofwater in a food system and vapour pressure of pure water at the same temperature. It is the ratiobetween the vapour pressure of the food itself, when in a completely undisturbed balance withthe surrounding air media, and the vapour pressure of distilled water under identical conditions.Pure water has an aw of 1 . Free water in fruits and vegetables is the water available for chemicalreactions, to support microbial growth and to act as a transporting medium for compounds. Thereexists a relationship between ‘Equilibrium Relative Humidity (ERH)’ and water activity (aw) andis equally important because of the common factor ‘Vapour Pressure’. Where, ERH is defined as

the relative humidity of the air surrounding the food at which the product is in equilibrium withthe environment, i.e., it neither gains moisture nor loses it. A saturated solution of sodiumchloride has a water activity of 0.755 and this same concentration of solution in a closedcontainer will develop an equilibrium relative humidity (ERH) in a head space of 55.5 per cent.Hence the relationship at the same vapour pressureis given as;

ERHaw = ------------------

100The water activity of 0.80 means that the vapour pressure is 80 per cent of that of pure water atthat particular temperature. Also, the water activity increases with rise in temperature. Foodswith water activity around 0.95 or more provide sufficient moisture to support the growth ofspoilage organisms including bacteria, yeasts and molds.Most of the spoilage causing organisms grow in a apecific moisture condition and thus isreferred to as critical water activity, below which growth cannot occur. Intermediate Moisturefoods have water activity values in a range of 0.65 to 0.90. Fig.1indicates the range of wateractivity for various types of food products, where the water content is also important.

Source: Elisavita Sandulachi. 2012.

Intermediate Moisture Food is an age old concept of food preservation in which traditionalingredients were just added to food to achieve specific water activity (aw) while maintaining thesufficient water content for acceptability and palatability of food products. With theadvancement in the field of Science and Technology involving food and increased concern offood scientists towards reducing spoilage of food products, new ingredients namely humectantsand preservatives have been used in the development of new IMF’s. it is important to understandthat IMF’s take into account both water activity (aw) as well as moisture content of the food andthus sometimes the range of water activity (between 0.6-0.9) and moisture content (between 10-50 per cent) varies amongst a wide range. Many other factors including pH, Eh (electrical

potential/ redox), F (High temperature), T (Low temperature) values, use of preservatives, microflora etc also affect the preservation quality of food products including IMF’s.

Different preservation methods viz., dehydration, osmotic dehydration and dry infusionmay be used to adjust water activity during the preparation of IMF’s. Water content of suchproducts may vary between 20-50 per cent to get an acceptable intermediate moisture level inproducts which are softer, moist and ready to eat (Cemeroglu, 1986). Different preservationmethods that can be used to reduce the water activity in food products are categorized as:

1. Partial drying: It is the simplest and cheapest method of food preservation, ‘sun drying’.In most parts of the country open sun drying is still practiced for drying fruits, raisins,fish and similar type of food products. However, on commercial levels, large sizeddehydrators, ovens and dryers can be used to reduce the water content and to control thewater activity (aw).

2. Osmotic drying (Moist infusion): This method of drying is based on the principle of‘osmosis’ in which different humectants, eg., sugars, salt, alcohols, polyols, organic acidsand proteins etc are used. The difference in the osmotic pressure of the food and thesolution used acts as the driving force between the two components. Thus, water in thefood material diffuses into solution and humectants diffuses into food material. Thismethod is used in the preparation of candid foods and preserves where sugar is used as ahumectant.

3. Dry infusion: This method is recommended for the preparation of high quality ofdehydrated preserved products. This is also an energy intensive method of dehydrationwhere fruits are first dehydrated and then soaked in required humectants until the desiredwater activity is achieved.

4. Blending or formulation: This is the most recent method of dehydration and its ease ofuse makes it more popular amidst food producers. Here, the food is mixed with requiredingredients including humectants and the food mixture is applied to required cooking,baking or extrusion technique to achieve the required water activity in the final product.It is time saving, energy efficient and more flexible method to get a desired type ofproduct including preserves, confectionery items, snacks and pet foods.

Types of Intermediate Moisture Foods:The main purpose of IMF is to get the desirable water activity in the final product besidesmaintaining enough moisture content in the final product to ensure its palatability and shelflife. The technique is very useful in the preservation of fruits and vegetables withoutrefrigeration. Use of sugar or salt as humectants helps to achieve the desired water activity asthey act as water activity depressant. Also, addition of preservatives provides the margin ofsafety against spoilage organisms making these foods stable even at room temperature.Some of the examples of IMF’s include: Murabba Candied fruits/veg/rhizome/fruit peel Crystallized fruit

Jam, jellies, marmalade Dehydrated fruits Dehydrated vegetables Raisins Dates Seedless tamarind Dried apricots Dates paste Honey

Safety of intermediate Moisture FoodsThe principle and technique for the preparation of Intermediate Moisture Foods is very reliableas it provides margin of safety against the spoilage causing microorganisms. However,Staphylococcus aureus is one of the organism of high concern in these food products as theseorganisms can tolerate the water activity as low as 0.83 to 0.86 under aerobic conditions and afavorable pH. In addition some other organisms like S. faecalis, Lactobacillus spp., Aspergillus,Penicillium and others could also be a cause of concern when the water activity of the foodproduct is deviated. The table (s) 1 and 2 below illustrates some of the microorganisms and rangeof their water activity.

Table 1 Water activity and growth of microorganisms

Source: Maria S Tapia et, al., 2007

Table 2 Water activity and growth/ toxin production by moulds

Source: Maria S Tapia et, al., 2007

In addition to using sugars and salt to control water activity, some chemical preservativesincluding sulfites, sorbic acid, citric acid, benzoic acid, propionic acid, phosphoric acid andascorbic acids are widely used in the preparation of IMF’s (Welti-Chanes et al., 1997). Also,propylene glycol, a humectant with specific antimicrobial activity and sorbates & propionates asmould inhibitors, are used for the stabilization of these products. These additives can be used incombination as and when required as per the pH and water activity of the final product.

Some kind of deteriorative chemical reactions i.e., non-enzymatic browning and lipid oxidation,dramatically increase in IMF’s. These biochemical changes are especially due to the presence ofreducing sugars and amino groups in the food products. Inclusion of peels may trigger lipidoxidation which can be easily avoided or controlled with Good Manufacturing Practices and/ orby avoiding heat treatment. The reaction of sugar with amino group, also called as Maillardreaction, develops brown pigments and sometimes it is a desirable change in some of the foodproducts. However, to completely avoid the undesirable browning of the food products, use orinvolvement of pentose sugars viz., ribose, xylose and arabinose should be avoided.

As far as products from fruits are concerned, action of enzymes cannot be completely avoided.The browning reaction initiated by Poly Phenol Oxidase (PPO) is not a new problem in fruitproducts. It is a faster reaction and causes sensory unacceptability and nutritional losses in fruitbased products. As these are heat sensitive enzymes and IMF involves avoiding use of heattreatment, an exposure of food products to 70-90OC for short durations will control the enzymeactivity.

FSSAI recommendations for IMF

The regulations called as ‘Food Safety and Standards (Food Products Standards and FoodAdditives) Regulations, 2011’ suggests general and specific standards for various categories offood products. The regulations defines the Intermediate Moisture Foods in its own way, as;

1. Murabba or Preserve: means the product prepared from suitable , sound whole or cut,grated fruits, rhizome or vegetables, appropriately prepared, suitable for the purpose,singly or in combination, by impregnating it, with nutritive sweetners to a concentrationadequate to preserve it. It should have TSS- 65 per cent and fruit content not less than 55per cent.

2. a) Candied fruits/ vegetables/ rhizome/ fruit peel means the product prepared from soundripe fruits, vegetables, rhizomes or fruit peel, of any suitable variety, appropriatelyprepared by impregnating it with nutritive sweeteners to a concentration adequate topreserve it.b) Crystallised fruits/ vegetables/ rhizome/ fruit peel means the product prepared from

candied product by coating with pure crystallized sugar or by drying the syrup on wetcandied fruit.

c) Glazed fruits/ vegetables/ rhizome/ fruit peel means the product prepared fromcandied product by coating it with a thin transparent layer of heavy syrup with orwithout pectin which has dried to a more or less firm texture on the product.

All these three types of products should have not less than 70 per cent total sugar ofwhich 25 per cent should be of reducing sugar to total sugar.

3. The regulation defines Jam, jellies and marmalade extensively and suggests that theseproducts should be prepared from any fruit ingredient singly or in combination. The fruitcontent in these products not to be less than 45 per cent, except from the fruits ofstrawberry, raspberry and ginger, where the fruit content should be 25 per cent, 23 percent in cashew apples and 8 per cent in passion fruit, by weight. TSS should be 65 percent for jams and 60 per cent for jellies and marmalades. Some other substances that maybe added to these products are cane sugar, sucrose, dextrose and invert sugar, liquidglucose, honey, salt, herbs, spices, condiments and their extracts and other ingredientsappropriate to the product whose standards are prescribed in the regulations. Pectinextracted from other fruits may be added at GMP level. As per the regulations the jam,jelly and marmalade should have original colour and flavor, consistency should be freefrom objectionable materials, defects and fermentation etc.

4. Dehydrated fruits: is the product prepared from edible part of suitable variety of soundfruit, free from blemishes, insect or fungal infections, of appropriate maturity, fromwhich, moisture has been removed, under controlled conditions of temperature, humidityand air flow, to the extent that the product is preserved. The product shall have moisturecontent not more than 20 per cent.

5. Dehydrated vegetables: is the product, prepared from edible portions of suitable varietyof sound vegetables, free from insect or fungal infection, free from blemishes, suitablyprepared, from which moisture has been removed under controlled conditions oftemperature, humidity and air flow, to the extent that the product is preserved. The finalproduct should have uniform colour and shall be free from discolouration due toscorching or enzymatic reactions. The regulations give specifications for the followingparameters in dehydrated vegetables:

S.No. Name ofvegetable

Moisturenot morethan (%)

SO2 notmore than(ppm)

Total ashnot morethan (%)

Ashinsolubledil HCl notmore than(%)

Peroxidasetest

1 Green leafy veg. 7 2000 Negative2a Tubers like arvi 7 2000 Negativeb Lotus root

tapioca6 2000 Negative

c Yam 6 2000 NegativeD Carrot 6 2000 NegativeE Potato 6 2000 Negative3 Karela 6 2000 Negative4 Cabbage 6 2000 Negative5 Okra 8 2000 Negative6 Other vegetables 8 2000 5 0.5 Negative7 Powders of

onion & garlic5 2000 5 0.5 Negative

8 Powders of otherveg. includingtomatoes

5 2000 5 0.5 Negative

6. Raisins means the product obtained by drying sound, clean grapes of proper maturitybelonging to Vitis vinifera L.,. The product may be washed, with or without seeds andstems and may be bleached with sulphur di oxide. The product shall be free from foreignmatter, living insects, mould, dead insects, insect fragments and rodent contamination.The product shall have uniform colour, pleasant taste and flavor, free from odour andtaste and evidence of fermentation. The product shall be free from added colouringmatter. The product shall conform to the following:

1 Moisture (m/m) Not more than 15.0 per cent2 Damaged raisins (m/m) Not more than 2.0 per cent3 Sugared raisins (m/m) Not more than 15.0 per cent

7. Dates means the product obtained by drying sound, clean fruits of proper maturitybelonging to Phoenix dactylifera. The product may be washed, pitted or unpitted, with orwithout cap, pressed or loose. The product may be treated with sugar, glucose syrup.Flour and vegetable oil. The product shall be free from foreign matter, living insects,mould, dead insects, insect fragments and rodent contamination. The product shall havepleasant taste and smell, free from odour and evidence of fermentation. The product shallbe free from added colouring matter. The product shall conform to the following:

1 Moisture (m/m) Not more than 30.0 per cent2 Ash insoluble in dil HCl Not more than 0.1 per cent3 Blemished/ damaged units Not more than 5.0 per cent4 Extraneous matter Not more than 1.0 per cent

8. Seedless tamarind ;a) Tamarind (without seed) shall be obtained from Tamarindus indica L., after removal

of outer covering and seeds from mature and ripe fruits.

b) It shall be clean and will not contain deleterious substances, obnoxious odour,external moisture and inorganic extraneous matter.

c) It shall be free from insect infestation, live or dead insects, mould growth, rodent hairand excreta, added colouring matter and impurities of animal origin.

d) It shall also conform to the following standards;1 Moisture content Not more than 20.0 per cent2 Organic extraneous matter

(w/w)Not more than 5.0 per cent

3 Total ash w/w (on dry basis) Not more than 6.0 per cent4 Acid insoluble ash w/w (on

dry basis)Not more than 1.0 per cent

5 Crude fibre w/w (on drybasis)

Not more than 9.0 per cent

6 Tamarind seeds Not more than 0.5 per cent9. Dried Apricots means products prepared from sound, ripe fruit of varieties of Armeniaca

vulgaria lam. (Prunus armenica L.) and processed by sun drying or by other methods ofdehydration. The product shall have colour characteristics of the variety and the type oftreatment and shall have flavor and odour characteristic of the product. The product shallbe free from living insects or mites and reasonably free from extraneous vegetable matter,insect debris and other objectionable matter. The product can be whole (unpitted), whole(pitted), halves and/ or slabs consisting of portions of sound, ripe apricots ofcharacteristic colour, irregular in shape, size and thickness and excluding whole fruit. Theproduct shall conform to the following standards:

S.No. Characteristics Requirement1 Moisture content % w/w (max)a Dried apricots not treated with any

preservatives20

B Dried apricots treated with permittedpreservatives

25

2. DefectsSlabs % (w/w) maximum 10.0 Total shall

not be morethan 15.0 percent w/w

Damaged fruits % (w/w) Maximum 10.0Broken fruits % (w/w) maximum 10.0Insect damaged and dirty fruits %(w/w) maximum

5.0

Mouldy fruit % (w/w) maximum 1.0Immature fruits % (w/w) maximum 10.0

10. Date paste, means product prepared from fruits of date plam (Pheonix) that are sound,consistent in colour and texture, harvested at the stage of maturity, washed, pitted andcapped. Dates used for making date paste shall be free from diseases and contain no

parthenocarpic or unripe fruits. They shall be free from fermentation and mould, insectsfragments, eggs, larvae, dirt and foreign matter. Date paste shall be soft and have noalteration in smell and flavor. It shall not contain whole or broken pits, stalks orextraneous matter. The product shall be from single variety of dates or a blend of severalvarieties of dates. No ADDITIVES are allowed in this paste. It shall conform to thefollowing standards:

1 Moisture % by weight Not more than 20.0 per cent2 Total Ash % by weight Not more than 1.2 per cent3 Acid insoluble ash % by

weightNot more than 0.1 per cent

11. Honey; shall be the natural sweet substance produced by honey bees from the nectar ofblossoms or from secretions of plants, which honey bees collect, transform and store inhoney combs for ripening. It shall possess pleasant aroma, sweet flavor and tastecharacteristic of honey. Honey shall be free from organic and inorganic matter includingvisible mould, insects and insect debris, fragments of bees, brood, pieces of bees wax,grains of sand, and any other extraneous matter. Honey consists essentially of othersugars, predominantly fructose and glucose as well as other substances such as organicacids, enzymes and solid particles derived from honey collection. The colour of honeyvaries from nearly colourless to dark brown. The consistency can be fluid, viscous orpartly to entirely crystallized. Honey sold as such shall not have added to it any foodingredients, including food additives, nor shall any other addition be made other thanhoney. Honey shall comply with the following requirements:S.No. Parameters Limits1 Specific gravity at 27OC, Min. 1.352 Moisture per cent by mass Max. 203 Total reducing sugars, per cent, by mass

Min.65

Carvia callosa and Honeydew honey, percent, by mass, Min.

45

4 Sucrose, per cent, by mass, Max 5Carvia callosa and Honeydew honey, Max. 10

5 Fructose to Glucose ratio (F/G Ratio) 0.95-1.506 Total ash per cent, by mass, Max 0.507 a) Acidity expressed as formic acid per

cent, by mass, Max.0.20

b) Free acidity milli equivalents acid/1000 g, Max

50.0

8 Hydroxy Methyl Furfural (HMF) mg/kg,Max

80.0

9 Diastase activity, Schade units, Min. 310 Water insoluble matters per cent, by mass,

Max0.10

11 C4 sugar, per cent, by mass, Max. 7.012 Pollen count/ g, Min 2500013 Specific marker for rice syrup (SMR) Negative14 Trace marker for Rice syrup (TMR) Negative15 Foreign oligosaccharides per cent, Max. 0.116 Proline, mg/kg, Min 18017 Electrical conductivity

a) Honeys not listed under Honey dew,Max.

0.8 mS/ cm

b) Honeys listed under Honeydew, Min. 0.8 mS/ cm18 a) ∆ δ 13C Max (Maximum difference

between all measured δ 13C values);per mil

+2.1

b) ∆ δ 13C Fru-Glu (The difference in13C/12C ratio between fructose andglucose); per mil.

+1.0

c) ∆ δ 13C (per cent) Protein- Honey(The difference in 13C/12C ratiobetween honey and its associatedprotein extract); per mil.

>-1.0

Honey shall not be heated or processed to such an extent that its essential composition is changedand / or its quality is impaired. The product can be labeled according to floral or plant source, ifit comes from any particular source, and has the organoleptic, physicochemical and microscopicproperties corresponding with that origin: in the case of ‘Monofloral honey’ the minimum pollencontent of the plant species concerned shall not be less than 45 per cent of total pollen contentand in case of ‘ multi-floral honey’, the pollen content of any of the plant species shall notexceed 45 per cent of the total pollen content. ‘Honey dew honey’ comes mainly from excretionsof plant sucking insects of order Hemiptera on the living parts of plants or secretions of livingparts of plants.

11. LECTURE NOTES

(Prepared By: Dr. Deepali Bajpai)

Tomato Products: Concept And Standards

Tomato (Lycopersicum esculentum L.) which belongs to family Solanaceae is one of themost important and popular vegetable plants in the world. Tomatoes aside from being tasty, arevery healthy too plays an important role in balance nutrition as they are a good source ofVitamins A and C. Tomatoes are consumed in diverse ways including raw as an ingredient inmany dishes, tomato ketchup, sauce, salad & drink. The plants typically grow to 1-3 meter (3-10ft) in height while tomatoes are botanically berry type fruits.

In India the average yield of tomato is 9.6 tonnes per hectare. India is the world’s secondlargest producer, but process less than 1% of its production. In India, though production oftomato is increasing the growth of tomato processing industry is slow. Tomatoes are availableduring the season at cheaper rate i.e. 2 rupees/kg and price start shooting up 80 Rs/Kg during offseason. This impacts farmers by way of high post -harvest losses and low returns during periodsof market glut. Therefore, in India there is good potential to develop tomato products based smallscale industry at village or block level. Tomato products such as puree, Juice, ketchup, sauce,Paste, cocktail can be produced.

The following rules should be kept in mind to develop high quality tomato products :

1. To use only plant ripened tomatoes.

2. During processing use only stainless steel or wooden make equipments. Never use iron andcopper based equipment this will change the colour of tomato product red to brown or black.Tomatoes contain lycopene pigment, which is self –oxidizing isomer of carotene, which turnsto brown in colour when it comes to contact with iron. Iron also forms a black compoundwith tannin which is present in spice and tomatoes.

3. Avoid prolonged heating and cool the product quickly after preparation.

The following products can be made:

1 .Tomato Juice: For making of tomato juice collect only plant-ripened red tomatoes. Thetomatoes, washed, trimmed,steamed , crushed in a crusher or cut into pieces. The crushed piecesare heated in steam jacketed kettle till they become softened .The heated tomatoes have passedthrough the pulping machine using a fine mesh sieve skin.The sugar and salt 1%% is added andheated to 85-900 C. The hot juice then filled in bottles, sealed immediately and processedsterlized in boiling water for about 30 minutes and cooled.

2. Tomato Puree: The first step of tomato puree is same as tomato juice preparation. Theconcentrated juice under vaccum to about 9 to 12% total solid to get tomato puree. The tomatopuree is filled with bottles, crown corked and processed in boiling water for 30 minutes andcooled.

3. Tomato Ketchup: Tomato ketchup is popular in India. It is made from concentrated tomatojuice or pulp without seeds and pieces of skin. The tomato juice concentrated with spices such ascardamom, pepper, cinnamon and other ingredients etc are tied loosely in a muslin cloth andplaced in boiling juice in steam jacketed kettle. The sugar, salt and acetic acid are added to theextent that the ketchup contains not less than 12 percent tomato solids and 28 per cent totalsolids.

4. Dehydrated tomato slice: Dehyderation involves slow removal of water from the tomato forincreasing shelf life. The drying of tomato depends on a variety of tomato, temperature, humidityof air during the drying, thickness of the slices and efficiency of the dehydrator or oven. Dryingcan be done in the sun, oven or use of a dehydrator. In a dehydrator heated air is circulated anddrying may take less than six hours depending on the tomato variety. Dehydrated products areusually of higher quality than sun dried products. It is important to turn the slices during drying.Packaging and storage is done in airtight jars or food grade plastic bags. Properly dried tomatoesshould be dark red lathery, not brittle and non-sticky.

5.Tomato powder: The tomato juice is converted into a free flowing, highly hygroscopicpowder by using different drying methods. Sometimes the natural tomato flavor in powder formis incorporated to compensate any loss of flavor to yield a full strength juice powder. Juice canbe converted to powder by using different methods like spray drying, roller drying and foam matdrying.

6. Tomato Cocktail: The tomato cocktail contains tomato juice to which common salt, vinegar,Worcestershire sauce, lemon or lemon juice etc. are added in different proportions to suit thepalate. It is prepared just before use or sometimes also served from the stock. The general recipefor tomato cocktail is as follows

Ingredients Quantity

Tomato Juice 5 liter

Common salt 100 g

Spices (Cumin, Cardamom, coriander seed,cinnamon, black pepper)

2g (each)

Cloves (Headless) 5 Numbers

Red chili powder 5g

Vinegar 300ml

Method: Simmer the tomato juice, with the spices loosely tied in a cloth bag for about 20minutes in a covered vessel. Then add vinegar and common salt. After mixing all the ingredientsthe cocktail is ready, it is boiled hot as the temperature at 82-880C in pre sterilized bottles. Thebottles are closed and kept immersed in boiling water for 30 minutes.

Quality control and Standards

The food product order (FPO) 1955 of the Govt of India is mandatory for tomato products. Thetomato products should confirm to specifications laid down in FPO

FPO Standard of tomato juice:

1. The colour of juice is deep red in colour.

2. The juice should possess the characteristics of taste and flavor of tomatoes.

3. The acidity of the juice as citric acid is about 0.4%.

4. The vitamins like beta carotene present in fresh tomatoes should go into the juiceduring its preparation.

5. Selection of tomatoes should be from one stock for uniformity in colour.

6. The only substances that may be added are salt (1.5%W/W), sugar, dextrose,malic acid, ascorbic acid, citric acid and permitted colour.

7. The minimum total soluble solids free of salt shall be 5% (W/W)

8. The mould count shall not exceed 30% of the field examined.

9. Harmful poisonus metals in tomato juice shall not be more than1ppm(lead),100ppm (copper on the dried tomato solid basis) 2ppm (arsenic),250ppm (tin) and 19ppm (Zinc).

FPO Standard for tomato puree and paste

1. Fresh, fully ripe on plants, free from insect and pest tomatoes should be selected.

2. The juice free from skin and peels.

3. The tomato puree and paste not showed any sign of fermentation at 370C for seven days.

4. In puree and paste common salt, citric acid, ascorbic acid, spices, permitted colour andpreservatives is recommended.

5. The mold count in the finished product shall not exceed 60% in the field examined.

6. The minimum percentage of soluble soilds (W/W) free of salt in tomato paste and tomatopuree should be 25% and 9% respectively and sodium benzoate 250 ppm.

7. Tomato Ketchup: 25%total solids, acidity: 1.0%, Sodium Benzoate: 750ppm

The Bureau of Indian standards has laid down the following specifications for tomato products:

1. Tomato Juice: IS:3881:1966

2. Tomato Ketchup: IS:3882:1966

3. Tomato Purees: IS: 3883: 1966

Problems with preparation of tomato products

Black neck: Formation of black ring in the neck region of bottle is known as black neck. Itcaused by iron, which gets into the product from the material of the equipment and cap on thecrown wall through the action of acetic acid. The iron comes into the contact with tannins inspice forms ferrous tannate which is oxidized to ferric tannate. It can be prevented:

1. Filling of hot sauce and ketchup at a temperature not less than 850C.

2. Reducing contamination by iron.

3. Addition of 100ppm SO2 or milligram ascorbic acid using cloves only after removing thehead portion of clove.

Flow sheet for Tomato Juice

Tomato

Washing

Sorting and Trimming

Cutting and Chopping

Heating at 70-900C

Pulping/extraction of Juice

Addition of salt, sugar and citric acid

Homogenization

Heating at 82-880 C for a minute

Filling hot into bottles/cans

Sterlizing in boiling water for 30 minuts

Cooling

Sealing

Flow sheet for Tomato puree and Paste

Tomato Juice or pulp (Strained)

Concenteration (open Kettle/Vaccum Pan)

Hot filling into bottles or can (82-880C)

Thermal processing

Cooling

Storage

12. LECTURE NOTES

Preservation by Dehydration /Drying

The practice of drying of food stuffs, specially fruits and vegetables, for preservingthem is very old. The term ‘drying’ and ‘dehydration’ means the removal of water. The formerterm is generally used for drying under the influence of non-conventional energy sources like sunand wind. If fruits (or) vegetables are to be sun dried, they (or) their pieces should be evenlyspread in single layer (on) trays or boards and exposed to the sun. In sun drying there is nopossibility of temperature and humidity control. The hottest days in summer are, therefore,chosen so that the foods dry very fast, thus preventing them from getting spoiled due to souring.Souring (or) turning acidic is usually due to growth of microorganisms which convert thecarbohydrates in the food to acid. Quick removal of moisture prevents the growth of themicroorganisms.

Dehydration means the process of removal of moisture by the application of artificialheat under controlled conditions of temperature, humidity and air flow. In this process a singlelayer of fruits (or) vegetables, whole or cut into pieces (or) slices are spread on trays which areplaced inside the dehydrator. The initial temperature of the dehydrator is usually 43oC which isgradually increased to 60-66oC in the case of vegetables and 50-71 oC for fruits.

Advantages of dried / dehydrated foods

Dried foods are in more concentrated form than foods preserved in other ways. They are lesscostly to produce than canned or preserved food, because of lower labour costs and becauseof no sugar is required.

Due to reduction in bulk of the product, it requires less storage space.

The weight of a product is reduced to 1/4th to 1/9th its original (or) fresh weight and

thus the cost of its transport is reduced.

Sundrying

Sundrying of fruits and vegetables is practiced widely in tropical and subtropicalregions where there is plenty of sun shine and practically little or no rain during the dryingseason. Sundrying in direct (or) diffused sunlight (shade drying), one of the earliest method offood preservation, is still used for the production of dried fruits, and also for drying nuts. It wasoriginally limited to fruits high in sugar content, which when harvested, would dry naturallywithout hazard of loss from fermentation and molding.

Process for drying of fruits

Fruits (mature and free from insects and disease→ Washing → Peeling / removal of outer skin→ Preparation → Pretreatments → Spreading on flat wooden trays → Sulphuring → Drying

→Sweating → Packaging in air tight tin containers (or) polythene bags → Storage (at ambienttemperature).

Pretreatments

Lye peeling

Dipping the fruits (grapes and dates) in 0.5% to 2.5% boiling caustic soda solution for 0.5to 2.0minutes depending on their nature and maturity. Hot lye loosens the skin from the flesh bydissolving the pectin. The peel is then removed easily by hand. Any trace of alkali is removed bywashing the fruit thoroughly in running cold water (or) dipping it for a few seconds in0.5% citric acid solution.

Sulphuring

Sulphuring is done only for fruits and not vegetables. So2 fumes act as a disinfectantand prevent the oxidation and darkening of fruits on exposure and thus improves their colour.This phenomenon is generally seen in sliced fruits which darken due to oxidation of thecolouring matter. Sulphur fumes also act as a preservative, check the growth of molds etc. andprevent cut fruit pieces from fermenting while drying in the sun. Vitamins in sulphured fruits areprotected but not in unsulphured ones.

The whole fruits, slices (or) pieces are exposed to the fumes of burning sulphur inside aclosed chamber known as sulphur box for 30-60 min. or in small airtight rooms.

Sulphur box is a closed airtight chamber of galvanized iron sheet. It is fitted in awooden frame work having runways on both sides to hold the trays. For small scale sulphuring, abox of size of 90 x 60 x 90 cm which can hold 11 trays, each of 80 x 60 x 5 cm size is suitable. Abox holding 10 trays will require burning of about 3 g of sulphur in one charge.

Sweating

Keeping dried products in boxes or bins to equalize moisture content.

Sun drying of fruits

1. BananaDried ripe banana is known as ‘banana fig’. The fruit is peeled, sliced lengthwise,

sulphured and dried in the sun. Unripe bananas are peeled after blanching in boiling water andcut into discs for drying. The dried slices are either cooked or fried. They can also be convertedinto banana flour which can be used as such or in combination with cereal flours.2. Date

In the hard dried dates, sucrose sugar predominates, whereas in the soft dried dates,invert sugars predominates. Dates are picked in the dung stage, that is when the tip of the fruithas turned a translucent brown. They are spread on mats for 5 to 8 days for curing. This is

rather expensive as several pickings have to be made as the date attain other proper stage ofripening. Scientists have found that dates could be picked 3 to 4 days before the “dung” stageand then dipped for ½ to 2 min in 0.5-2.5 % caustic soda solution before placing them for dryingin order to get a good dried product.

3. Fig

The fruits are allowed to ripen on the tree and gathered when they drop. They are thenspread thinly on the drying yard for 3 to 4 days for drying. After drying they are sorted andpacked. Figs are treated with salt and lime (1 kg of each per 1000 litrs of water) to remove thehair from the skin and also to soften the flesh. They are then dried without sulphuring, till there isexudation of juice on pressing the dried fig between the fingers.

4. Grapes

Large quantities of seedless grapes known as kishmish grapes are imported into Indiafrom Afghanistan. Ripe bunches of grapes are hung inside dark rooms known as kishmishkhanas till the berries acquire a greenish or light amber tint. These shade dried grapes areconsidered to be a far superior to the ordinary sundried (or) dehydrated grapes. The otherimportant dried grape called ‘Monucca’ (or) Rasisin is prepared from the large seeded Haithagrapes which are lye dipped prior to the sun drying.

For efficient drying, grapes should have a high sugar content of 20 to 24 degree brix.From this point of view, some of the varieties of grapes are not suitable for drying. The highersugar content grapes are dried without any sulphuring till there is no exudation of juice onpressing dried grape between the fingers. The yield and quality of the final dried product dependon the brix of the fresh grape taken for drying.

In California, the Sultanina (or) Thompson seedless varieties of grapes are dried. Thegrapes are sometimes dipped for 3-6 seconds in caustic soda and sodium bicarbonate, coveringthe surface of a solution with a thin layer of olive oil. This treatment removes only the wax andthe bloom on the grapes without cracking the skin. The dried product has a glossy appearance.Lye dipped grapes are sometimes treated with sulphur fumes, for 3-5 hrs for bleaching them,because certain markets prefer such glossy product.

In Australia, potassium carbonate solution with a layer of olive oil (or) sometimesgrape seed oil itself, is used for dipping the grapes. The drying is carried out on wire net racksarranged inside a shed. In this way, the grapes are dried without direct exposure to the sun.Drying takes 10-20 days depending upon the variety of grape. The dried product is generally ofhigh quality.

5. Jack fruit

Jack fruit bulbs of ripe fruit are sliced and the seeds removed. The slices are dried with(or) without sulphuring. The bulbs can also be made into a fine pulp, which can be dried in theform of sheets or slabs.

6. Mango

Unripe, green mangoes are peeled, sliced and dried in the sun. The dried product is usedfor the preparation of mango powder which is added as a relish in various food preparations.Ripe mangoes are taken and the juicy pulp squeezed by hand. The pulp is spread on Bamboomats and a small quantity of sugar sprinkled over it. Whet the first layer has dried, another layerof pulp is spread over it for drying. This process is repeated until the dried slab is 1.2 to 2.5 cmthick. The dried product has a light yellow amber colour and possess a delicious taste.

Other fruits

Pomegranate seeds are dried, and the dried product known as anardana is sued as asavoury and acidulant like tamarind in cooking. Apple rings are threaded and dried by hangingthem out to dry in the sun.

The cereals, pulses and oilseeds are usually sundried in most of the areas afterharvesting from the crop. Sundried vegetables results poor quality in physical and chemicalcharacteristics during storage.

Types of drier

Drier type Usual food type

I. Air convection driers

1. Kiln drier Pieces

2. Cabinet, tray or pan drier Pieces, purees, liquids

3. Tunnel drier Pieces

4. Continuous conveyor belt drier Purees, liquids

5. Belt trough drier Pieces

6. Air lift drier Pieces, granules

7. Fluidized bed drier Small pieces, granules

8. Spray drier Liquids, purees

II. Drum (or) Roller drier

1.Atmospheric driers Purees, liquids

2.Vacuum driers Purees, liquids

III.Vacuum driers

1.Vacuum shelf Pieces, purees, liquids

2.Vacuum belt Purees, liquids

3.Freeze driers Pieces, liquids

Methods of drying

I. Air convection driers

All air convection driers have some sort of insulated enclosures, a means of circulatingair through the enclosure and a means of heating this air. They also will have various means ofproduct support, special devices for dried product collection, some will have air driers to lowerdrying air humidity.

Movement of air generally will be controlled by fans, blowers and baffles. Air volumeand velocity will affect drying rate, but its static pressure also is important since products beingdried become very light and can be blown off trays or belts.

The air may be heated by direct or indirect methods. In direct heating the air is in directcontact with flame (or) combustion gases. In indirect heating the air is in contact with a hotsurface, such as being blown across pipes heated by steam, flame or electricity. The importantpoint is that indirect heating leaves the air uncontaminated. On the other hand in direct heatingthe fuel is seldom completely oxidized to CO2 and water. Incomplete combustion leaves gasesand traces of soot and this is picked up by the air and can be transferred to the food product.Direct heating of air also contributes small amounts of moisture to the air since moisture is aproduct of combustion but this is usually insignificant except with very hygroscopic foods. Thesedisadvantages are balanced by the generally lower cost of direct heating of air compared toindirect heating, and both methods are widely used in food dehydration.

1. Kiln drier

Kiln driers of early design were generally two storey constructions. A furnace or burneron the lower floor generated heat, and warm air would rise through a slotted floor to the upperstory. Foods such as apple slices would be spread out on the slotted floor and turned overperiodically. This kind of drier generally will not reduce moisture to below about ten per cent. Itis still in use for apple slices.

2. Cabinet, Tray and Pan driers

Food may be loaded on trays or pans in comparatively thin layers upto a fewcentimeters. Fresh air enters the cabinet is drawn by the fan through the heated coil and is thenblown across the food trays to exhaust. In this case the air is being heated by the indirect method.Screens filter out any dust that may be in the air. The air passes across and between the trays inthis design. The air is exhausted to the atmosphere after one pass rather than being recirculatedwithin the system. The moisture laden air, after evaporating water from the food,would have to be dried before being recirculated, or else it would soon become saturated andfurther drying of the food would stop.

Cabinet, tray and pan driers are usually for small scale operations. They arecomparatively inexpensive and easy to set in terms of drying conditions. They may run upto 25trays high, and will operate with air temperatures of about 93oC dry bulb and air velocities ofabout 2.5 to 5.0 M/5 across the trays. The commonly are used to dry fruit and vegetable pieces,and depending upon the food and the desired final moisture, drying time may be of the order or10 of even 20 hr.

3. Tunnel and continuous belt drier

For larger operations we elongate the cabinet, place the trays on carts. If drying time tothe desired moisture is 10 hr then each wheeled cart of trays will take 10 hr to pass through thetunnel. When a dry cart emerges it makes room to load another wet crat into the opposite end ofthe tunnel. Such an operation becomes semi continuous.

A main construction feature by which tunnel driers differ has to do with the direction ofair flow relative to tray movement. The wet food carts move from left to right. The drying airmoves across the trays from right to left. This is the counter flow or countercurrent principle. Itssignificance is that the air, when it is hottest and driest, contacts the nearly dry product, whereasthe initial drying of entering carts gets cooler, moisture air that has cooled and picked uptomoisture going through the tunnel. This means that the initial product temperature and moisturegradients will not be as great and the product is less likely to undergo case hardening or othersurface shrinkage leaving wet centers. Further, lower final moistures can be reached since thedriest product encounters the dried air. In contrast, there also are concurrent flow tunnels withthe incoming hottest, driest and travelling in the same direction. In this case rapid initial dryingair slow final drying can cause case hardening and internal splits and porosity as centers finallydry, which sometimes is desirable in special products.

Just as carts of trays can be moved through a heated tunnel, so a continuous belt may bedriven through a tunnel or oven enclosure. Then we have a continuous belt or conveyor drier anda great number of designs are possible.

4. Belt trough drier

A special kind of air convection belt drier is the belt trough drier in which the beltforms a trough. The belt is usually of metal mesh and heated air is blown up through the mesh.The belt moves continuously, keeping the food pieces in the trough in constant motion tocontinuously expose new surface. This speeds drying and with air of about 135oC, vegetablepieces may be dried to 7-5% moisture in about 1 hr.

But not all products may be dried this way since certain sizes and shapes do not readilytumble. Fragile apple wedges may break. Onion slices tend to separate and become entangled.Fruit pieces that exude sugar on drying tend to stick together clump with the tumbling motion.These are but a few additional factors that must be considered in selecting a drier for a particularfood.

5. Air lift drier

Several types of pneumatic conveyor driers go a step beyond tumbling to expose moresurface area of food particles. These generally are used to finish dry materials that have beenpartially dried by other methods, usually to about 25% moisture, or at least sufficiently low sothat the material becomes granular rather than having a tendency to clump and mat.

6. Fluidized bed drier

Another type of pneumatic conveyor drier is the fluidized bed drier. In fluidized beddrying, heated air is blown up through the food particles with just enough force to suspend theparticles in a gentle boiling motion. Semidry particles such as potato granules enter at the leftand gradually migrate to the right, where they are discharged dry. Heated air is introducedthrough a porous plate that supports the bed of granules. The moist air is exhausted at the top.The process is continuous and the length of time particles remain in the drier can be regulated bythe depth of the bed and other means. This type of drying can be used to dehydrate grains, peasand other particulates.

7. Spray driers

The most important kind of air convection drier is the spray drier. Spray driers turn outa greater tonnage of dehydrated food products than all other kinds of driers combined, and thereare various types of spray driers designed for specific food products.

Spray driers are limited to foods that can be atomized, such as liquids and low viscositypastes or purees. Atomization into minute droplets results in drying in a matter of seconds withcommon inset air temperatures of about 200oC. Since evaporative cooling seldom permitsparticles to reach above about 80oC (180oC) and properly designed systems quickly remove thedried particles from heated zones, this method of dehydration can produce exceptimally highquality with many highly heat sensitive materials, including milk, eggs and coffee.

In typical spray drying we introduce the liquid food as a fine spray or mist into a toweror chamber along with heated air. As the small droplets make intimate contact with the heated airthey flash off their moisture, become small particles and drop to the bottom of the tower fromwhere they are removed. The heated air which has now become most is withdrawn from thetower by a blown or fan. The process is continuous in that liquid food continues to the pumped

into the chamber and atomized, along with dry heated air to replace the moist air that iswithdrawn, and the dried product is removed from the chamber as it descends.

Milk and coffee powder is usually dried in the spray drier. Thermoplastic materials /substances viz., fruit juices are spray dried in a specially developed BIRS spray drier.

8. Drum (or) Roller driers

In drum (or) roller drying, liquid foods, purees pastes and mashes are applied in a thinlayer onto the surface of a revolving heated drum. The drum generally is heated from within bysteam. Drier may have a single drum or a pair of drums. The food may be applied between thenip where two drums come together, and then the clearance between the drums determines the

thickness of the applied food layer, or the food can be applied to other areas of the drum. Food isapplied continuously and the thin layer loses moisture. At a point on the drum or drums a scraperblade is positioned to peel the thin dried layer of food from the drums. The speed of the drum isso regulated that the layer of food will be dry when it reaches the scraper blade, which also isreferred to as a doctor blade. The layer of food is dried in one revolution of the drum and isscrapped from the drum before that position of the drum returns to the point where more wetfood is applied. Using steam under pressure in the drum, the temperature of the drum surfacemay be well above 100oC, and is often held at about 150oC. With a food layer thicknesscommonly less than 2 mm, drying can be completed in 1 min or less, depending on the foodmaterial. Other features of drum driers include hoods above drums to withdraw moisture vaporand conveyers in troughs to receive and move dried product.

Typical products dried on drums include milk, potato mash, heat tolerant purees such astomato paste, and animal feeds. But drum drying has some inherent limitations that restrict thekinds of foods to which it is applicable. To achieve rapid drying, drum surface temperature mustbe high, usually above 120oC. This gives products a more cooked flavour and colour than whenthey are dried at a lower temperature. Drying temperature can, of course, be lowered byconstructing the drums within a vacuum chamber but this increases equipment and operatingcosts over atmospheric drum or spray drying.

A second limitation is the difficulty of providing zoned temperature control needed tovary to drying temperature profile. This is particularly important with thermoplastic foodmaterials. Whereas dried milk and dried potato are easily scraped from the hot drum in brittlesheet form, this is not possible with many dried fruits, juices and other products which tend to besticky and semimolten when hot. Such products tend to crimp, roll up, and otherwise accumulateand stick to the doctor blade in a taffy like mass.

This condition can be substantially improved by a cold zone to make the tacky materialbrittle just prior to the doctor blade. But zone controlled chilling is not as easy to accomplish ona drum of limited diameter and therefore limited arc, as it would be in perhaps 6 m of length of ahorizontal drying belt 45 m long. One means of chilling is by directing a stream of cool air onto asegment of the product on the drum prior to the doctor blade.

For relatively heat resistant food products, drum drying is one of the least expensivedehydration methods. Drum dried foods generally have a somewhat more cooked character thanthe same materials spray dried; thus drum dried milk is not up to beverage quality but issatisfactory as an ingredient in less deligately flavoured manufactured foods. More gentlevacuum drum drying or zone-controlled drum drying increases dehydration costs.

9. Vacuum driers

Vacuum dehydration methods are capable of producing the highest quality driedproducts, but costs of vacuum drying generally also are higher than other methods which do notemploy vacuum. In vacuum drying, the temperature of the food and the rate of water removal are

controlled by regulating the degree of vacuum and the intensity of heat input. Heat transfer to thefood is largely by conduction and radiation.

All vacuum drying systems have four essential elements. These include a vacuumchamber of heavy construction to withstand outside air pressures, that may exceed internalpressures by as much as 9800 kg/cm2; means to supply heat; a device for producing andmaintaining the vacuum; and components to collect water vapour as it is evaporated from thefood.

The vacuum chamber generally will contain shelves or other supports to hold the foodand these shelves may be heated electrically or by circulating a heated fluid through them. Theheated shelves are called platens. The platens convey heat to the food in contact with them byconduction, but where several platens are one above another they also radiate heat to the food onthe platen below. In addition, special radiant heat sources such as infrared elements can befocussed onto the food to supplement the heat conducted from platen contact.

The device for producing and maintaining vacuum will be outside the vacuum chamberand may be a mechanical vacuum pump or a steam ejector. A steam ejector is a kind ofaspiration in which high velocity steam jetting past an opening draws air and water vapour fromthe vacuum chamber by the same principle that makes an insect spray gun draw fluid from thecan.

The means of collecting water vapour may be a cold wall condenser. It may be insideto vacuum chamber or outside the chamber but most come ahead of the vacuum pump so as to

prevent water vapour from entering and fouling the pump. When a steam ejector can condensewater vapour as it is drawn along the air from the vacuum chamber and so a cold wall vapourcondeser may not be needed except where a very high degree of efficiency is required.

Degree of vacuum

Atmospheric pressure at sea level is approximately 15 psi, or sufficient pressure tosupport a 30 inch column of mercury. This is equivalent to 760 mm of Hg or 1 in Hg isapproximately 25 mm. At 1 atm or 30 in., or 760 mm of Hg, pure water boils at 100oC. At 10 inor 250 mm of Hg pure water boils at 72oC. At 2 in. or 50 mm of mercury pure water boils at38oC. High vacuum dehydration operates at still lower pressures such as fractions of mm of Hg.Freeze drying generally will operate in the range of 23 mm down to about 0.1 mm of Hg.

There are two kinds of vacuum drier.

a. Vacuum shelf driers Batch typeIf liquids such as concentrated fruit juices are dried above about 55 mm Hg, the juice

boils and splatters, but in the range of about 3 mm Hg, and below, the concentrated juice puffs asit loses water vapour. The dehydrated juice then retains the puffed spongy structure. Sincetemperature well below 40oC can be used, in addition to quick solubility there is minimumflavour change or other kinds of heat damage. A vacuum shelf drier is also suitable for thedehydration of food pieces. In this case, the rigidity of the solid food prevents major puffing,

although there also is a tendency to minimize shrinkage.

b. Continuous vacuum belt drier Continuous type drier

This drier is used commercially to dehyderate high quality citrus juice crystals, instanttea and other delicate liquid foods.

The drier consists of a horizontal tank like chamber connected to a vacuum producing,moisture condensing system. The chamber is about 17 m long and 3.7 m in diameter. Within thechamber are mounted two revolving hollow drums. Around the drum is connected a stainlesssteel belt which moves in a counter clock wise direction. This drum on the right is heated withsteam confined within it. This drum heats the belt passing over it by conduction. As the beltmoves, it is further heated by infrared radiant elements. The drum to the left is cooled with coldH2O circulated within it and cools the belt passing over it. The liquid food in the form of aconcentrate is pumped into a feed pan under the lower belt strand. An applicator roller dippinginto the liquid continuously applies a thin coating of the food onto the lower surface of a movingbelt. As the belt moves over the heating drum and past the radiant heaters, the food rapidly

dries in the vacuum equivalent to about 2 mm Hg. When the food reaches the cooling drum, it isdown to about 2% moisture. At the bottom of the cooling drum is a doctor blade which scrapesthe cooled, embrittled product into the collection vessel. The belt scrapped free of productreceives additional liquid food as it passes the applicator roller and the process repeats incontinuous fashion.

Products dried with this equipment have a slightly puffed structure. If designed, agreater degree of puffing can be achieved. This has been done in the case of milk by pumpingnitrogen gas under pressure into the milk prior to drying. Some of the gas goes into solution inthe milk. Upon entering the vacuum chamber this gas comes out of solution violently and furtherpuffs the milk as it is being dried.

10. Freeze dryer

Freeze drying can be used to dehydrate sensitive high value liquid foods such as coffeeand juices, but it is especially suited to dry solid foods of high value such as straw berries, wholeshrimp, chicken dice, mushroom slices and sometimes food pieces as large as steaks and chops.These types of foods, in addition to having delicate flavours and colors, have textural andappearance attributes which cannot be well preserved by any current drying method exceptfreeze drying. Any conventional drying method that employs heat would cause considerableshrinkage distortion and loss of natural strawberry structure (texture), upon reconstitution such asdried strawberry would not have the natural colour, flavour or turgor and would be more like astrawberry preserve or jam. This can be largely prevented by drying from the solidly frozen state,so that in addition to low temperature, the frozen food has no chance to shrink or distort whilegiving up its moisture.

The principle behind freeze drying is that under certain conditions of low vaporpressure, water can evaporate from ice without the ice melting. When a material can exist as asolid, a liquid and a gas but goes directly from a solid to a gas without passing through the liquid

phase. The material is said to sublime. Dry ice sublimes at atmospheric pressure and roomtemperature. Frozen water will sublime if the temperature is 0oC or below and the frozen H2O isplaced in a vacuum chamber at a pressure of 4.7 mm (or) less. Under such conditions the H2Owill remain frozen and water molecules will leave the ice block at a faster rate than watermolecules from the surrounding atmosphere reenter the frozen block.

Within the vacuum chamber heat is applied to the frozen food to speed sublimation andif the vacuum is maintained sufficiently high usually within a range of about 0.1 to 2 mm g andthe heat is controlled just short of melting the ice, moisture vapour will sublime at a nearmaximum rate. Sublimation takes place from the surface of the ice, and so as it continues the

ice front recedes towards the center of the food piece; i,e. the food dries from the surface inward.Finally, the last of the ice sublimed and the food is below 5% moisture. Since the frozen foodremains rigid during sublimation, escaping H2O molecules leave voids behind them, resulting inporous sponge like dried structure. Thus freeze dried foods reconstitute rapidly but also must beprotected from ready absorption of atmospheric moisture and O2 by proper packaging.

A heating plate is positioned above and below the food to increase heat transfer rate butan open space is left with expanded metal so as not to seal off escape of sublimed H2Omolecules. Nevertheless, as drying progresses and the ice front recedes, drying rate drops off forseveral reasons. Thus the porous dried layer ahead of the reducing ice layer acts as an effectiveinsulator against further heat transfer and the porous layer slows down the rate of escape of H2Omolecules subliming from the ice surface.

11. Foam mat dryer

The foam is deposited on a perforated tray or belt support as a uniform layerapproximately 3 mm thick. Just before the perforated support enters the heated oven it is given amild air blast from below. This forms small craters in the stiff foam which further expands foamsurface and increases drying rate. At oven temperatures of about 82oC foam layers of manyfoods can be dried to about 2 to 3% moisture in approximately 12 min.

13. LECTURE NOTES

CANNING OF FRUITS AND VEGETABLES(Prepared By: Dr. S.S. Shukla and Dr. Priti Jain)

CanningThe process of sealing foodstuffs hermetically in containers and sterilizing them by heatfor long storage is known as canning. In 1804, Appert in Frarice invented a process ofsealing foods hermetically in containers and sterilizing them by heat. Appert is known asthe 'Father of Canning'. This work formed the foundation for modern canning procedure.In honor of the inventor, canning is also known as appertizing. Saddington in Englandwas the first to describe a method of canning of foods in 1807. In 1810, Peter Durand,another Englishman, obtained the first British Patent on canning of foods in tincontainers. In 1817, William Underwood introduced canning of fruits on a commercialscale in U.S.A. Fruits and vegetables are canned in the season when the raw material isavailable in plenty. The canned products are sold in the off-season and give betterreturns to the grower.

Principle and Process of Canning

Destruction of spoilage organisms within the sealed container by means of heat

Process

1) Selection of fruits and vegetables

I. Fruits and vegetables should be absolutely fresh.II. Fruits should be ripe, but firm, and uniformly mature. Over-ripe fruits should be

rejected because they are infected with microorganisms and give a poor qualityproduct.

III. Unripe fruits should be rejected because they generally shrivel and toughen onIV. canning.V. All vegetables except tomatoes should be tender.

VI. Tomatoes should be firm, fully ripe and of deep red colour.VII. Fruits and vegetables should be free from dirt.VIII. They should be free from blemishes, insect damage or mechanical injury.

2) GradingThe selected fruits and vegetables are graded according to size and colour to obtainuniform quality. This is done by hand or by machines such as screw grader androller grader. Fruits like berries, plums and cherries are graded whole, whilepeaches, pears, apricots, mangoes, pineapples, etc., are generally graded aftercutting into pieces or slices.

3) Washing

It is important to remove pesticide spray residue and dust from fruits and vegetables.One gram of soil contains 1012 spores of microorganisms. Therefore, removal ofmicroorganisms by washing with water is essential. Fruits and vegetables can bewashed in different ways. Root crops that loosen in soil are washed by soaking inwater containing 25 to 50 ppm chlorine (as detergent). Other methods of washingare spray washing, steam washing, etc.

4) Peeling

The objective of peeling is to remove the outer layer. Peeling may be done in variousways.a) Hand peeling

It is done mostly in case of fruits of irregular shape, e.g., mango and papaya,where mechanical peeling is not possible.

b) Steam peelingFree-stone and clingstone peaches are steam peeled in different ways. Theformer are cut and steam washed. Potatoes and tomatoes are peeled by steamor boiling water.

c) Mechanical peelingThis is done in case of apples, peaches, pineapples and cherries and also forroot vegetables like carrots, turnips and potatoes.

d) Lye peelingFruits like peaches, apricots, sweet oranges, mandarin oranges and vegetableslike carrots and sweet potatoes are peeled by dipping them in 1 to 2 percentboiling caustic soda solution (lye) for 30 seconds to 2 minutes depending on theirnature and maturity. Hot lye loosens the skin from the flesh by dissolving thepectin. The peel is then removed easily by hand. Any trace of alkali is removedby washing the fruit or vegetable thoroughly in running cold water or dipping it fora few seconds in 0.5 per cent citric acid solution. This is a quick method whereby cost and wastage in peeling is reduced.

e) Flame peelingIt is used only for garlic and onion which have a papery outer covering. This isjust burnt off. Vegetables like peas are shelled, carrots are scraped, and beansare snipped or trimmed.

f) Flame peelingIt is used only for garlic and onion which have a papery outer covering. This isjust burnt off. Vegetables like peas are shelled, carrots are scraped, and beansare snipped or trimmed.

5) CuttingPieces of the size required for canning are cut. Seed, stone and core are removed.Some fruits like plum from which the seeds cannot be taken out easily are cannedwhole.

6) Blanching

It is also known as scalding, parboiling or precooking. Fruits are generally notblanched leaving the oxidizing enzyme system active. Sometimes fruit is plunged fora given time-from half to, say, five minutes, according to variety-into water at from180°F to 200°F, and then immediately cooled by immersion in cold water. The objectis to soften the texture and so enable a greater weight to be pressed into thecontainer without damage to the individual fruit. Blanching is usually done in case ofvegetables by exposing them to boiling water or steam for 2 to 5 minutes, followedby cooling. The extent of blanching varies with the toed. This brief heat treatmentaccomplishes the following:

I. Inactivates most of the plant enzymes which cause toughness, discolouration(polyphenol oxidase). mustiness, off-flavour (peroxidase), softening and lossof nutritive value.

II. Reduces the area of leafy vegetables such as spinach by shrinkage or wilting,making

III. their packing easier.IV. Removes tissue gases which reduce sulphides.V. Reduces the number of microorganisms by as much as 99%.

VI. Enhances the green colour of vegetables such as peas, broccoli and spinach.VII. Removes saponin in peas

VIII. Removes undesirable acids and astringent taste of the peel, and thusimproves flavor

IX. Removes the skin of vegetables such as beetroot and tomatoes which helpsin their peeling.

DisadvantagesI. Water-soluble materials like sugar and anthocyanin pigments are leached by

boiling water.II. Fruits lose their colour, flavour and sugar

7) CoolingAfter blanching, the vegetables are dipped in cold water for better handling andkeeping them in good condition.

8) FillingBefore filling, cans are washed with hot water and sterilized but in developingcountries these are subjected to a jet of steam to remove dust and foreign material.Automatic, large can-filling machines are used in advanced countries but choice

grades of fruits are normally filled by hand to prevent bruising in India. Hand filling isthe common practice. After filling, covering with syrup or brine is done and thisprocess is called syruping or brining.

9) Exhausting

The process of removal of air from cans is known as exhausting. After filling andlidding or clinching, exhausting is essential. The major advantages of exhausting areas under:

I. Corrosion of the tinplate and pin holing during storage is avoided.II. Minimizes discolouration by preventing oxidation.

III. Helps in better retention of vitamins particularly vitamin C.IV. Prevents building of cans when stored in hot climate or at high altitude.V. Reduces chemical reaction between the container and the contents.

VI. Prevents development of excessive pressure and strain during sterilization.

Containers are exhausted either by heating or mechanically. The heat treatmentmethod is generally used. The cans are passed through a tank of hot water at 82 to87°C or move on a belt through a covered steam box. In the water exhaust box, thecans are placed in such a manner that the level of water is 4-5 cm below their tops.The exhaust box is heated till the temperature of water reaches 82 to 1000c and thecentre of the can shows a temperature of about 79°C. The time of exhausting variesfrom 6 to 1 a minutes, depending on the nature of the product. In the case of glassjars or bottles, vacuum closing machines are generally used. The bottles or jars areplaced in a closed chamber in which a high vacuum is maintained. It is preferable toexhaust the cans at a lower temperature for a longer period to ensure uniformheating of the contents without softening them into pulp. Exhausting at hightemperature should be avoided because. The higher the temperature, the more isthe volume of water vapour formed, and consequently the greater the vacuumproduced in the can.

10) SealingImmediately after exhausting the cans are sealed airtight by means of a can sealer.In case of glass jars a rubber ring should be placed between the mouth of the jarand the lid, so that it can be sealed airtight. During sealing the temperature shouldnot fall below 74°C.

11) ProcessingHeating of foods for preserving is known as processing, however, in canningtechnology processing means heating or cooling of canned foods to inactivatebacteria. Many bacterial spores can be killed by either high or very low tempera-ture. Such drastic treatment, however, affects the quality of food. Processing timeand temperature should be adequate to eliminate all bacterial growth. Moreover,over-cooking should be avoided as it spoils the flavour as well as the appearance ofthe product. Almost all fruits and add vegetables can be processed satisfactorily at atemperature of 100°C, i.e., in boiling water. The presence of acid retards the growth

of bacteria and their spores. Further, they do not thrive in heavy sugar syrup which isnormally used for canning of fruits. Vegetables (except the more acid ones liketomato and rhubarb) which are non-acid in nature, have a hard texture, andproximity to soil which may infect them with spore-bearing organisms are processedat higher temperatures of 115 to 121ºC. The sourness of fruits and vegetables is dueto their acid content (measured in pH) which has a great influence upon thedestruction of microorganisms. The lower the pH the greater is the ease with which aproduct can be processed or sterilized. Fruits and vegetables can be classified intothe following four groups according to their pH value.

Class pH Product

Low acid(called 5.0non-acid)

Above 5.0 Vegetable such as peas, lima bean,asparagus, cauliflower, potato, spinach, beet,corn, french bean

Medium acid 4.5-5.0 Turnip, carrot, okra, cabbage, pumpkin, beet,greenbean, etc., and products like soups andsauces

Acid 3.7-4.5 Tomato, pear, banana, mango, jackfruit,pineapple,sweet cherry, peach, apple

High acid Below 3.7 juice, rhubarb, prune, sauerkraut pickle,chutn

Bacterial spores can be more easily destroyed at pH 3.0 (fruits) than at pH 5.0 to6.0 (vegetables, except tomato and rhubarb). Bacterial spores do not grow orgerminate below pH 4.5. Thus, a canned product having pH less than 4.5 can beprocessed in boiling water but a product with pH above 4.5 requires processing at115 at 1210C under a pressure of 0.70 to 1.05 kg/cm2 (10 to 15 lb/sq inch). It isessential that the centre of the can should attain these high temperatures. Thetemperature and time of processing vary with the size of the can and the nature ofthe food: the larger the can, the greater is the processing time. The processing timefor different canned fruits and vegetables is given in the tables Under 'Canning ofFruits' and 'Canning of Vegetables'. Fruits and acid vegetables are generallyprocessed in open type cookers, continuous non-agitating cookers and continuousagitating cookers, while vegetables (non-acid) are processed under steam pressurein closed retorts known as automatic pressure cookers. In India, small verticalstationary retorts (frontispiece) are generally used for canned vegetable processing.The sealed cans are placed in the cookers, keeping the level of water 2.5 to 5.0 cmabove the top of the cans. The cover of the cooker is then screwed down tightly and

the cooker heated to the desired temperature. The period of sterilization(processing) should be counted from the time the water starts boiling. After heatingfor the required period the cooker is removed from the fire and the petcock isopened. When the pressure comes down to zero the cover is removed and thecans are taken out.

12) Cooling

After processing. the cans are cooled rapidly to about 39°C to stop the cookingprocess and to prevent stack-burning. Cooling is done by the following methods:

I. Dipping or immersing the hot cans in tanks containing cold water;II. Letting cold water into the pressure cooker specially in case of vegetables;

III. Spraying cans with jets of cold water; andIV. Exposing the cans to air.

Generally the first method, i.e., dipping the cans in cold water, is used. If cannedproducts are not cooled immediately after processing, peaches and pears becomedark in colour, tomatoes turn brownish and bitter in taste, peas become pulpy withcooked taste and many vegetables develop flat sour (become sour).

13)Storage

After labelling the cans, they should be packed in strong wooden cases orcorrugated cardboard cartons and stored in a cool and dry place. The outer surfaceof the cans should be dry as even small traces of moisture sometimes inducerusting. Storage of cans at high temperature should be avoided, as it shortens theshelf-life of the product and often leads to the formation of hydrogen swell. Themarketable life of canned products varies according -to the type of raw materialsused. Canned peach, grapefruit, pineapple, beans, spinach, pea etc., can be storedfor about two years, while pear, apricot, carrot, beetroot, tomato, etc., can be storedfor a comparatively short period only.

Containers for packing of canned products

Both tin and glass containers are used in the canning industry, but tin containers arepreferred.

Tin containersTin cans are made of thin steel plate of low carbon content, lightly coated on both sideswith tin metal. It is difficult to coat the steel plate uniformly and during the process ofmanufacture small microscopic spots are always left uncoated, although the coatingmay appear perfect to the eye. The contents of the can may react with these uncoatedspots resulting in discolouration of the product or corrosion of the tin plate. When thecorrosion is severe, black stains of iron sulphide are produced. It is necessary,therefore, to coat the inside of the can with some material (lacquer) which preventsdiscolouration but does not affect the flavour or wholesomeness of the contents. Thisprocess is known as "lacquering".

Two types of lacquers are used;

A. Acid-resistantAcid-resistant lacquer is a golden coloured enamel and cans coated with it arecalled R-enamel or A.R cans. These cans are used for packing acid fruits which areof two kinds (a) those whose colouring matter is insoluble in water, e.g., peach,pineapple, apricot, grapefruit, and (b) those in which it is water-soluble, e.g.,raspberry, strawberry, red plum and coloured grape. Fruits of group (a) are packedin plaincans and those of group (b) in lacquered cans.

B. Sulphur-resistantThis lacquer is also of a golden colour and cans coated with it are called C-enamelor S.R. cans. They are meant for non-acid foods only and should not be used forany highly acid product as acid eats into the lacquer. These cans are used for pea,corn, lima bean, red kidney bean, etc.

Size of cans: The sizes of cans in general use are given below:

Trade name of canSize (mm)

Al 68 x 102

1-lb Jam 78x 90

AJ-T 78 x 119

A2 87 x 114

1-lb Butter 103 x 70

A 2-lb Jam 103 x 102

A 21/2 103 x 119

7-lb Jam 157 x 148

A 10 157 x 178

Recently, a midget can has become highly popular for fruit juices, mango nectar, etc.Itholds about 165 ml of beverage and is a very popular picnic pack.

Tin containers are preferred to glass containers because of certain advantages:

I. Ease of fabrication,II. Strength to withstand processing,

III. Light weight,IV. Ease in handling,V. Cheapness, and

VI. Can be handled by high speed machines.

Causes of spoilage of canned foods

Spoilage of canned products may be due to two reasons:(A) Physical and chemical changes, and(B) Microorganisms.

(A)Spoilage due to physical and chemical changes

1. SwellWhen the ends of an apparently normal and perfect can with good vacuumbecome bulged it is termed as 'Swell' or 'Blower'. The bulge is due to the positiveinternal pressure of gases formed by microbial or chemical action. Hydrogen swell

This type of bulging is due to the hydrogen gas produced by the action of foodacids on the metal of the can. The bulging ranges from 'Flipping' to the 'HardSwell'. The food generally remains free of harmful microorganisms and is fit forconsumption.

FlipperThe can appears normal, but when struck against a tabletop one or both endsbecome convex and springs or flips out, but can be pushed back to normalcondition by a little pressure. Such a can is termed as "flipper" and may be aninitial stage of swell or hydrogen swell. It may also be caused by overfilling,under-exhausting or gas pres- sure due to spoilage.

SpringerA mild swell at one or both ends of a can is called a 'springer' which maybe aninitial' stage of hydrogen swell or be due to insufficient exhausting or overfillingof the can. The bulged ends (or at least one end) can be pressed back to theoriginal position, but will again become convex after some time.

Soft swellAt a more advanced stage, swell develops at both ends of the can which canbe pressed and returned to normal position, but springs back when thepressure is removed. A swell of this type is termed as "soft swell" and is moreor less similar to that of flipper.

Hard swellThis is the final stage of swell. The bulged ends cannot be pressed back tonormal position and the cans ultimately burst.The following precautions arenecessary to prevent the formation of hydro-gen swells:

a) Good quality tin plate should be used for making the cans. The quality isrelated to the porosity of the tin coating. The greater the porosity, thegreater is the possibility of corrosion of the can. The porosity can, however,be decreased by increasing the thickness of the coating and making it moreuniform. Plain cans are less susceptible to hydrogen swell formation thanlacquered cans.

b) About '0.5 per cent citric acid should be added to the syrup used for canningfruits of low acidity such as cherry, mango, papaya, etc. Citric acid checksthe formation of hydrogen swell to a great extent.

c) Before placing the lid a head space of 0.6 to 0.9 cm should be left in the canwhich is to be exhausted. The lid should be placed firmly or clinched beforeexhausting to ensure a

d) high vacuum in the can.e) Cans should be exhausted for a fairly longtime, but without affecting the

quantity of the product unduly. The larger the quantity of oxygen remainingin the can, the greater would be the corrosion because oxygen combineswith the nascent hydrogen formed by the action of acid on the tin container.In the absence of air, the rate of corrosion is low. Oxygen can be excludedfrom the can by filling it properly and exhausting it thoroughly.

f) The sealing temperature should not be below 74°C.g) At high storage temperature hydrogen formation will be more.

2. OverfillingSpoilage due to overfilling is common. During retorting, overfilled cans becomestrained due to expansion of the contents, and in the absence of vacuum in themswelling takes place. If the cans are properly heat exhausted, the excess materialoverflows from it due to expansion and thus spoilage because of overfilling is"avoided.

3. Faulty retort operationWhen the steam pressure is reduced rapidly at the end of processing, highpressure develops inside the cans resulting in their distortion and the cans whencooled look like "swells". Cans of very thin tin plate should not be used as theycannot withstand the pressure which develops in the cans while processing.

4. Under-exhaustingCans are exhausted to remove most of the air. This helps in the" proper filling offruits and vegetables and also creates a good vacuum, which is necessary toaccommodate any pressure that might develop inside the can as a result ofproduction of hydrogen due to corrosion. Improperly exhausted cans may suffersevere strain during heat processing due to the large internal pressure of the gaspresent in it. Under-exhausted cans show strain ranging from slight flipping todistortion, depending upon the amount of gas evolved from the product and thesize of the head space. All the gas must be removed by tilting the can andpressing its ends. Longer exhausting at a lower temperature of about 79°C givesbetter results than a short one at about 87°C, provided the cans are closed at thesame temperature. The advantage of exhausting the cans is, however, quicklylost if they are allowed to cool down appreciably before closing. Any undue

cooling of cans after exhausting and before closing should, therefore, beavoided.

5. PanellingIt is generally seen in large sized cans that the body is pushed inward due to thehigh vacuum inside. This also occurs when the tin plate is thin or the cans arepressure cooled at very high pressure. In very severe cases, seam leakage mayoccur but normally this is not regarded as spoilage.

6. RustCans having external rust must be thoroughly examined after removing the rustand, if the walls show a pitted appearance, should be rejected as spoiled. Cansslightly" affected by rust if not used immediately should be rejected. Rust ismostly seen under the label and subsequently affects the label as well. Rustformation can be checked if the cans are externally lacquered.

7. Foreigil"flavoursDuring preparation, filling, storage or even transportation, conditions maybecome unhygienic and the products may develop foreign or "off-flavours". Ifunsuitable metallic containers are used, a "metallic flavour" develops. Flavour isan important characteristic for maintaining which packages must be examined atregular intervals.

8. DamageRough handling of cans due to carelessness or ignorance may damage them. Ifany cans show signs of leakage or severe distortion they must be rejected.

9. Undesirable textureTexture is another important characteristic, like flavour and colour, which isdetected easily by a consumer. In order to main- tain the standard of a product itstexture should be tested periodically. Although there are no precise parametersfor measuring texture, an instrument like "Tenderometer", which measures theresistance to shearing and relative tenderness, can be used for peas and beans.Calcium salts present in the water used for canning have a "toughening effect"on peas and beans, but such hardening is considered desirable for potatoes andtomatoes. Care should be taken that the processing of soft fruits does not resultin their becoming pulp.

10.Corrosion of cansCans become corroded or perforated due to the acidity of the contents, speciallyhighly acid fruits. In recent years, attempts have been made to reduce thespoilage by using improved lacquers for internal coating of cans.

11.LeakageA leaking can is known as a "Leaker". This may be due to: (i) defective seaming,(ii) nail holes caused by faulty nailing of cases while packing, (iii) excessiveinternal pressure due to microbial spoilage sufficient to burst the can, (iv) internalor external corrosion, and (v) mechanical dam- age during handling.

12.BreathingThere may be a very tiny leak in the can through which air can pass in anddestroy the vacuum. In such cases the food is damaged due to rusting of the cancaused by oxygen in the air but still remains fit for consumption.

13.BurstingThis may be caused by the excess pressure of gases produced bydecomposition of the food by microorganisms, or by hydrogen gas formed by thechemical action of food acids on the tin plate. In such cases the canned productcannot be used.

14.BucklingSometimes due to improper cooling, distortion of the can takes place resembling'swell'. Although the distortion can be corrected by pressing, the cans are oftenbadly strained and the contents become spoiled due to entry of microorganismsthrough the strained seams. This type of spoilage is known as "Buckling"Sometimes a peak or small ridge forms on the can which is known as "Peaking".

15.DiscolourationThis can be detected by visual examination of the can and its contents.Discolouration may be due to biological causes like enzymatic and nonenzymaticbrowning or metallic contamination. Enzymatic browning due to the enzymepolyphenol oxidase present in fruits and vegetables can be avoided by placingthe peeled and cut pieces in 2 per cent salt solution. Non-enzymatic browning iscaused by reactions between (i) nitrogenous compounds and sugars, (ii]nitrogenous compounds and organic acids, (iii) sugars and organic acids, and (iv)among organic acids themselves. These reactions are known as Maillardreactions. Metallic contamination is mainly due to iron and copper salts. Somefruits and vegetables contain tannins which react with the iron of the tin plate toform black ferric tannate, which spoils the appearance of the contents.Sometimes hydrogen sulphide gas is produced by the reaction between fruitacids and the tin coating, which in turn reacts with the iron 'of the tin plate to formblack iron sulphide. Discolouration is also caused by traces of copper (1 ppm)from the metal vessels used; in contact with hydrogen sulphide copper formsblack copper sulphide. Metallic contamination can be avoided by using glasscontainers, coating the interiors of cans with lacquer and also eliminating the useof iron and copper vessels.

16.Stack burningIf processed cans are not allowed to cool "own sufficiently before storing, thecontents remain hot for a long time. This is known as "stack burning" whichresults in discolouration, cooked flavour and very soft or pulpy product.Therefore, it is necessary to cool the cans quickly to about 39°C before storage.

Microbial spoilage

a) Pre-processing spoilage: This type of spoilage occurs because of the time gapbetween filling and heat processing of the containers. Although processingchecks the growth of organisms the gas already present in the can causesswelling and flipping, so delay between filling and processing must be avoided,and also at all stages in the preparation of raw materials for canning.

b) Under-processing spoilage: Under-processing of canned foods result in theirspoilage by thermophilic bacteria and mesophilic organisms and this is termed as"underprocessed" spoilage.

c) Infection due to leakage through seams: A large number of cans afterprocessing show signs of microbial spoilage due to leakage of 'Can seams. Canswhich are water-cooled are more likely to leak than air- cooled ones. In suchcases the cans mayor may not swell depending upon the type of organism and ifthere is a defect in the seam it permits free passage of the gas formed in the can.For reducing this type of spoilage the bacterial level of the cooling water shouldbe low and the cans should be properly exhausted to reduce seam strain.Moreover, buckling also allows the entry of microorganisms.

Canning Equipments

Fruit and Vegetable Washer Fruit Mill Crusher

Fruit and Vegetable Pulper Double Seamer BM 102 DS

Double Seamer BM 1 ADS Rotary Flat Can Body Reformer

Flanger Lid Embossing Machine

Can Body Beader Canning Retrot

Exhaust Box Double Semer

14. LECTURE NOTES

(Prepared By : Dr. S.S. Shukla and Dr. Priti Jain)

Packaging of Fruits and Vegetables

Packaging is a process that is intended to preserve food against spoilage and contamination andextend the shelf life. It provides many benefits such as containment (holding the product),protection (quality, safety, freshness), information (graphics, labels), utility of use orconvenience and important for dating indicators. It may be used as a promotion tool. The agroclimatic conditions of our country are ideal for agriculture and horticulture. Our country’seconomy is also predominantly agrarian. India is the largest producer of fruits in the world (46million tonnes) with a global share of over 10% and the second largest producer of vegetables(80 million tonnes) with a global share of over 15%. Inspite of all these achievements,agriculture contributes only one-third of the gross national product (GNP). About 20 to 30% ofthe produce is lost annually due to lack of adequate infrastructure and less use of modern postharvest technologies. In terms of value, the losses are Rs. 25,000 crores annually. This high levelof wastages and value losses are largely due to lack of basic infrastructure like storage andhandling facilities. Hence, per capita availability of fruits is decreased to around 80gms per day,which is half of the requirement of a balanced diet.

Purposes of packaging

Packaging provides the produce with attributes necessary to survive a number of differenthazards that can be expected during storage, transportation and distribution.

It protects raw or processed foods against spoilage and contamination by an array of externalhazards.

Packaging serves as a barrier in controlling potentially damaging levels of light, oxygen, andwater.

It facilitates ease of use, offers adequate storage, conveys information, and provides evidenceof possible product tampering by tamper-evident labels.

Hence, the step in selection of a package for a specific product is to obtain a clear picture of thedistribution pattern and a drawn up model that qualitatively and quantitatively represents thesystem through which the produce traverse. Package includes various types of distributionhazards like mechanical, climatic, biological contamination and other hazards. Packagingmaterials and the system followed plays an important role in prevention these losses at the farmand during the distribution chain. Packaging reduces wastes, adds value and makes the productqualitatively and quantitatively acceptable. In case of horticultural produce, packaging is

required not only to enhance the aesthetic value, but also to keep the produce in good conditionfor long periods. With the multifarious functions, the prospective of packaging has widenedsignificantly. Today, packaging is considered as one of the most important operations.

Product Characteristics

Horticultural products are highly perishable in nature and are very easily affected by climaticconditions, distribution hazards and microbial decay. Since fruits and vegetables are livingorganisms even after harvesting, they remain fresh only as long as normal metabolism continues.In order to develop a suitable package for horticultural produce, it is important to understand thebiology of the produce. Since the produce is a living tissue, even after harvesting, the highrespiration rate and other metabolic processes associated with maturation and ripening of theseproducts continue throughout the marketing cycle. This creates a special problem in the storageand packaging of fresh produce. While developing a packaging system, following productcharacteristics have to be considered

1) Respiration

Fresh produce respire even after harvesting. During this process, oxygen is used and carbondioxides is released. The rate of deterioration is proportional to the high respiration rate.Rapid respiration results in fast ripening/aging of the produce. If the availability of oxygen isrestricted, it results in changes in chemical reactions, breakdown of cells, production of smallquantities of alcohol, off-flavour and off odour and finally bringing about decay or spoilageof the fresh produce. Individual fruits and vegetables vary in respiration rates.

2) MoistureFruits and vegetables have very high moisture content 75% to 95%. Under ambientconditions, loss of moisture causes rapid drying of the product causing wilting, shrivelingand loss of rigidity. Loss in moisture results in weight loss during storage and transportation.

3) Micro-organismsAnother common type of spoilage of fresh fruits and vegetables is caused by micro-organisms such as yeast, bacteria and molds. If there is a surface bruise or injury to the fruit,micro-organisms invade through this and cause internal decay. Hence sorting, of fruits andvegetables is necessary before packaging.

4) Changes in Colour, Texture, Odour and FlavourDuring normal ripening, alterations takes place in the colour, texture, odour and flavor of thefresh produce. Beyond the ideal point of ripeness its quality deteriorates. Hence, the aimshould be to reach the fruits to the consumers in a perfect stage of ripeness.

5) Temperature

The process of respiration is dependent on temperature, therefore, it is necessary to showdown the reaction by storing the produce under refrigeration, Each fruit has an ideal storagetemperature. Very low temperature causes chilling injuries which damages the delicatetissues of the fresh produce.

6) VolatilesSome fresh produce give off volatile compounds such as ethylene during ripening. If thesevolatiles are not allowed to escape, unacceptable odour develops and the produce ripensrapidly. Ethylene production rate depends upon variety, maturity stage, temperature, oxygenlevel, carbon dioxide level of the fresh produce.

7) VentilationSince the horticultural products respire even after harvesting, the package should be providedwith ventilation holes during transportation. Cold air is constantly circulated through thecontainer to remove the heat transmitted during the cooling process.The quality of the fresh produce, when presented to the consumer depends on:a) Initial quality of the harvestb) Care taken during physical handlingc) Length of the time since harvestd) Storage environment

8) Pre-coolingThe aim of pre-cooling is to slow down the enzymatic and respiratory activity, minimizesusceptibility to micro-organisms and to reduce water loss and ethy lene production. Pre-cooling helps in removing the field heat prior to storage. It reduces the respiration heat, anddecreases the rate. The different methods used for pre-cooling are forced-air cooling, vacuumcooling and hydro cooling.

Packaging Requirements

Different horticultural products need different types of packages depending on their physical,anatomical and physiology (mainly transpiration, reparation and ethylene production rate) natureand susceptibility to microbial decay. Temperature, relative humidity and ventilation also plays avery important role in determining the post-harvest life of the fresh produce. Thus, the packagingrequirements for fresh produce can be summarized as:1. Protection against bruising and physical injury2. Protection against microbial contamination and deterioration3. Provide ventilation for respiration and exchange of gases4. Protect against moisture/weight loss5. Slow down respiration rate, delay ripening and increase storage life

6. Control ethylene concentrations in the package

Packaging MaterialsThe packages for fresh fruits and vegetables can be classified as:1. Consumer/Retail packs2. Transport/Bulk packs

1. Consumer PacksConsumer packages are small in size and designed to hole ½ dozen-1 dozen fruits or ½ kg to 2kg of vegetables. Many types of packages in terms of forms and materials are used as consumerpacks. The selection criterion for the type of consumer pack depends on marketingcharacteristics of the product. The most commonly used packages are listed below:

I. Flexible Plastic Films: Different types of flexible plastic films like LDPE(Polyethylene), PVC (Poly vinyl Chloride), PP (Polypropylene) and cellulose acetatefilms are used for packaging of horticultural produce. These films are mostly used aspouches with holes punched at regular intervals to allow respiration. They are available ina wide range of thicknesses and grades and can be engineered to control theenvironmental gases inside the pouch. LDPE is the most widely used material.

II. Trays with Overwrap: The trays used are usually made of molded pulp tray or plasticmaterial like EPS.PVC and PP. The produce is placed in individual cavities so thatabrasion and bruising is avoided during transportation. The trays also provide cushioningeffect to the produce. The overwrap film is a transparent see through food-grade,odourless plastic film with the property of clinging to the product packed when stretchwrapped. This film can be applied without the application of heat. It is usually made ofLDPE,LLDPE or PVC. The films are semi-permeable and allow exchange of gases forrespiration of the product.

III. Plastic Punnets: These are strong, versatile, clear, bright containers, which offer productvisibility and are provided with holes for ventilation, which keep the produce fresh.These containers are food-grade, odourless, light weight, stackable and recyclable andgive good presentation, They are either made of PET,PVC or PP.

IV. Plastic Net bags (Extruded & Woven): The plastic net bags have the feature to stretchand accommodate all sizes and shapes of produce. These bags are available in roll formor in precut lengths with stretch width or 200 mm- 400 mm. By allowing air to circulatein and around the produce, these net bags prolong the freshness and shelf0life of the freshproduce. They also eliminate pack condensation thereby preventing spoilage and

wastage. They make a colourful point of sale display by allowing clear visibility of thecontents, enhancing the natural colours of fresh produce. These are generally made ofHDPE (High Density Polyethlene ) or PA(Polyamide).

V. Foam Sleeve: This is aplastic tubular film made of polyethylene foam available indifferent colours, diameters and lengths. It can be easily slipped over the individual fruitsin a snug fit form. It provides a cushioning effect and protects the freshproduce againstabrasion and scratches during transit. It is hygienic, non-toxic and odourless.

VI. Light Weight Plastic Crates: These are lightweight crates, which need not be put intoan outer pack for transportation. The perforations provide ventilation and keep theproduce fresh. The crates are stackable and have high compression strength and thereforeprovide adequate protection to the fresh produce packed inside. These crates are hygienic,clean, and reusable and can be recycled. They can be made of HDPE or PP.

VII. Shrink Wrap: One of the newest trends in fresh produce packaging is the shrinkwrapping of individual produce. The greatest advantage of individual shrinks wrapping ofindividual produce. The greatest advantage of individual shrink wrapping is its ability tocontrol moisture loss. By reducing the transpiration rate and maintaining the fruitfirmness the film forms a barrierwhich increases the resistance to water vapour. Thetranspiration rate can be reduced 5 to 20 times using selective permeable plastic films.The individual fruit is loosely sealed in a flexible film. The film is then shrunk tightlyaround the produce by passing these packs through a heat shrunk tunnel where they areexposed to hot blown air for a very short period (few seconds). The fresh produce is thencooled by rapid ventilation. The films most commonly used are LDPE or LLDPE.

VIII. Corrugated Boxes/Cartons: Many fruits like mangoes, apples, grapes, etc. are packed insmall packs of 2-4 kgs, either in corrugated boxes made of paper board or polymers likepolypropylene. These boxes/cartons are light-weight with good compression strength.They can be printed to have a good shelf appeal.

IX. Metals: Metals such as: steel and aluminum are used in cans.A metal can forms a hermetic seal, which is a complete seal against gases and vapor entryor escape and it offers protection to the contents.Metal also is used for bottle closures andwraps.

X. Glass: Glass is derived from metal oxides such as silicon dioxide.It is used in forming bottles or jars (which subsequently receive hermetic seals), thusprotects against water vapor or oxygen loss or gain. The thickness of glass must besufficient to prevent breakage from internal pressure, external impact or thermal stress.

XI. Paper: Paper is derived from the wood and may contain additives such as aluminumparticle, plastic coating, Resins or waxes.

XII. Plastic: Plastic varies in its degree of thickness. Important properties of the many typesof plastics that make them good choices for packaging material include ; Flexible andstretchable Lightweight, Low-temperature formability, Resistant to breakage, with highburst strength, Strong heat sealability, Versatile in its barrier properties to O2, moisture,and light. Plastic also may be used in combination with other packaging materials suchas: metal (for lining cans),Paper (for moisture resistance),and glass (reduces bottlebreakage). Among the thousands of types of plastics that are created, little number ofpolymers utilized in food packaging. Some of the more commonly used plastics for food

products are: Polyethylene (PE):Is the most common, comprising 63% of total plasticpackagingand the least expensive plastic. It is a water-vapor (moisture) barrier andprevents dehydration and freezer burn.

2. Transport PacksTransport packages are designed for long distance transportation in capacities ranging from4-5 kgs to 20-25 kgs. These packs must withstand impacts, compression and vibration duringtransport. The transport packages can be broadly categorized as rigid containers made ofwood, corrugated fibre board or plastic and flexible containers such as sacks made of plastic.Along with these materials some traditional materials used are jute (jute sacks), woodenboxes and bamboo baskets.

The varieties of packaging materials used for transport packaging of horticultural produce arelisted:

XIII. Bamboo Baskets: Bamboo baskets are widely used even today as transport packs indomestic market. They are available in various shapes, sizes and designs but they do nothave rigidity and stackebility during long distance transport. Today plastic baskets orKilta’s have also ben developed and used for storage & transportation of fruits &vegetables.

XIV. Wooden Boxes: The conventional baskets have been replaced by wooden boxes as theygive better protection to the fresh produce against transportation hazards. They have highpuncture resistance, good tensile strength as well as compression strength; but theyoccupy more space and add o to the tare weight. Also, the nails cause injuries to theproduce during long transportation. However, the use of wooden boxes is discouragednow-a –days as it directly promotes deforestation.

XV. Corrugated Fibre Board/Plastic Boxes: Corrugated fibreboard boxes are widely usedas transport/ shipping containers for frsh produce because of the following advantages:

a) Low cost to strength and weight ratiob) Good cushioning propertiesc) Smooth and non-abrasive surfaced) Good printability on the outer surface of the boarde) Easy to set up and collapsible for storagef) Reusability and recyclableg) Can be manufactured in high volumesh) Can be provided with ventilation by punching holes

Since the CFB boxes have poor wet strength, now-a-days they are laminated with plasticfilm like LDPE, PP or PVC. Plastic corrugated boxes made of PP and HDPE are partlyreplacing CFB boxes because of their low weight to strength ratio, high degree of waterresistance and re-usability. However, its cushioning properties are not comparable toCFB.

XVI. Plastic Crates: These are usually made of HDPE or PP by injection moulding.Polyethylene has higher impact strength and a low degradation by ultra- violet radiation

while polypropylene has a better scratch resistance. The performance of both materialscan be improved by adding anti-oxidants and UV protectants (for sunlight protection).The advantages of plastic crates are:a) As these crates are strong and rigid they can be used for many journeys, making the

cost per journey relatively lowb) Different sizes and shapes are availablec) They can be easily cleaned and disinfectedd) They are strong and weather resistant and because of this they can be used in humid

areasThese crates are either of stackable, stack-nest or collapsible in design. Collapsible plasticcrates are the most expensive crates followed by stack-nest and then the stacking crates.The collapsible crates reduce the storage space requirement and transport cost of emptycontaingers. The normal capacity varies between 20-40 kgs.

XVII. Sacks: These are generally used to bring the raw materials from the field. The commonlyused materials are cotton, jute, plastic (HDPE, PP). They are very useful because of lowcost, high strength, re-usability and require less space for empties. However, they havelow protection against puncture, compression, vibration and impact injuries. They arepoor in stackability. These sacks are usually combined with bamboo baskets and woodenboxes to improve cushioning and reduce bruise injuries and losses during transportation.

New Trends in Fresh Produce PackagingMany of these traditional packaging materials have been modified and new materials/technologies in terms of rigidity, stackability, longer storage, ventilation, cushioning have beendeveloped for transport packaging of fresh produce. Salient features of these materials arediscussed here.

1. Jute Reinforced Plastics (JRP)Jute fibres and wood are combined with thermoplastic materials like LDPE, HDPE, formaking semi-righd as well as rigid boards. The film layer is placedon both sides of non-woven jute. The composite layers are pressed n a hydraulic press at the required temperaturefor a certain period of time depending upon the thickness of the thickness of the end productand the type of film used. These boards have good tensile strength, puncture resistance andmoisture barrier property. JRP are now being increasingly used for transport packaging ofhorticultural products.

2. Modified Atmosphere Packaging (MAP)Modified atmosphere packaging is a form of packaging involving the removal of air from thepackage and replacing it with a single or mixture of gases. The gas mixture used depends onthe type of the produce. The gaseous atmosphere changes continuously throughout the storagedue to factors like respiration and other biochemical changes of the produce and thepermeation of gases through the package. Fresh fruits and vegetables are living organismshaving high levels of respiration and other metabolic processes associated with maturation,ripening and senescence. The MAP system is a dynamic one where respiration andpermeation occurs simultaneously. Factory affecting both of these must be considered whendesigning a package.

The respiration in a package is influenced by:a) Quantity of the produceb) Stage of maturityc) Temperatured) Concentration of ethylene gase) Light intensity

The permeation of the package is influenced by:a) Type and nature of materialb) Thickness and surface area of the materialc) Temperature and relative humidity

d) Partial pressure gradients of O2 and CO2

All the above factors interact to create equilibrium levels of O2 and CO2 inside the sealedpackage. The selection of a film or a combination of more than one film (laminate) dependson the expected transpiration and respiration rates of the produce. For most of the freshproduce the film selected should be more permeable to CO2 than to O2 Most of thecommercially available are shown in below:

Table 1: Barrier Properties of Plastic Films

Films WVTR GTRO2 CO2 N2

Polyethylene, LD 18 7800 42000 2800Polyethylene, HD 7-10 2600 7600 650Polypropylene Cast 10-12 3700 10000 680Polypropylene,Oriented

4-5 2015 - -

Polybutylene 8-10 5000 - -Onomer 25-35 4650-6975 - -Ethylene-VinylAcetate

40-60 12000 50000 4900

Cellulose acetate - 325 13640 -Polystyrene 100-125 5000 18000 800Ethyl cellulose - 31000 77500 -Methyl cellulose - 1240 6200 -Polyvingl alcohol - 1 1 -Polyester 25-30 50-130 180-390 15-18Nylon 6 84-3100 40 158-190 14Rigid PVC 30-40 150-350 450-1000 60-150

Plastised PVC 15-40 500-30000 1500-40000 300-10000PV-DC-Copolymer 1.5-5.0 8-25 50-150 2-2.6Polyacylonitrile 78 12 17 3

WVTR- Water Vapour Transmission Rate, g/m2 24 hrs. atm, at 38 ⁰C and 90% RH for 25µfilm.

GTR- Gas Transmission Rate, ml/m2 24hrs. atm, at 25 ⁰C for 35 µ film.

Some of the characteristics of plastic films for MAP of fresh produce are:

a) Required permeabilities for the different gasesb) Good transparency and glossc) High tear strength and elongationd) Good thermal and ozone resistancee) Commercial suitabilityf) Ease of handling

MAP has a good potential as an alternative to low temperature storage for preserving fresfruits and vegetables, particularly tropical fruits and vegetables which possess a highrespiration rate and are and are sensitive to chilling injury. Howevey, ther are still practicaland theoretical difficulties limiting the commercial use of modified atmosphere packagingfor fresh produce.

Table 2: Shelf-Life of Fruits and vegetables Under MAP

Commodity Room Temperature Temp(⁰C)

Low TemperatureShelf-

life(Days)

O2 (%) CO2 (%) Shelf-life

(Days)

O2 (%) CO2 (%)

Banana(Robustahands)

11(16)

12-15 2.7-5.0 13 42 9.7-16.0 4.7-7.0

Plantains(Nendran) 11(3)

4.2 5.3 13 18(10)

- -

Carrots 10 12.0 4.0 - - - -Bell Peppers 10-13

(5)7.7 4.5 9 28

(14)14.0 4.5

Chillies 5(3)

8.4 8.0 12 23(14)

15.0 2.5

Okra 6(2)

7.0 8.0 - - - -

Tomatoes 16-18(18)

9.3 3.4 12 30-35(21)

- -

Figures in bracket indicate shelf-life without MAP

3. Active PackagingAnother way of modifying the atmosphere pack is by using “Active Packaging” Packaging istermed as “Active” when it preferment. The goal of developing such packaging is to create amore ideal match of the properties of the package to the package to other requirements of thefood. Active Packaging can be created by using oxygen scavengers, carbon dioxide

absorbents/emitters, ethanol emitters and ethylene absorbents. The appropriate absorbentmaterial is placed alongside the fresh produce. It modifies the headspace in the package andthereby and thereby contributes to the extension of shelf-life of the fresh produce.

Table 3: Active Packaging Principles Applied to Perishables

Principle ApplicationPorosity Control Gas Pressure Release, Gas Composition BalancePolymer PermeabilityControl

Gas Compensation Balance, Temperature Compensation

Melting of Waxes Temperature CompensationInorganic/ OrganicOxidation

Oxygen Scavenging, Oxygen Permeation Barrier OxygenScavenging

Enzyme Catalysis Oxygen ScavengingAcid/ Base Reaction CO2 Absorption, CO2 Generation, Odour AbsorptionAdsorption Taint Removel, Oxyegn Scavenging, Ethylene Scavenging,

Water RemovalAbsorption Condensation Control, Drip CollectionHydrolysis Sulfur Dioxide ReleaseDesorption Ethanol Release, Hinokitiol Release, Water ReleaseOrganic Reactions Ethylene Removel, Oxygen Barrier

4. Vacuum Packaging

Vacuum packaging is a method of packaging that removes air from the package prior to sealing.The purpose is usually to remove oxygen from the container to extend the shelf life of foods.