Pre and Post Harvest Losses in Crops, Fruit , vegetables

By

By Allah Dad Khan

Former DG AGRICULTURE Extension Khyber Pakhtunkhwa PROVINCE

0332-9221298

Agro climatic Conditions of Pakistan Agro-climatic conditions of Pakistan ranging from tropical to temperate allow

growing 40 different kinds of vegetables and 21 types of fruits and more than 20 crops including major crops.

Major vegetables grown in Pakistan include potato, onion, chilli, melons, cucurbits, tomato, turnip, okra and pea, whereas citrus, dates, mango, guava, apple, banana, apricot, grapes, almonds, peach, plum and pomegranate are the main fruit crops.

At present area under fruits and vegetables is 0.995 million ha (4.3% of the total cropped area) with the total production of 10.992 m

In Pakistan the magnitude of post harvest losses of vegetables and fruits is about 35%. Efforts are being made both at federal and provincial level to minimize these losses to safe guard the interest of growers, processors, traders, retailers and consumers million tonnes .

Factor for Pre and Post Harvest loss1.Soil fertility,

2.use of fertilizers.

3.Lack of plant foods in the soil can seriously affect the quality of fresh produce at harvest.

4.On the other hand, too much fertilizer can harm the development and post-harvest condition of produce.

Some of the effects are:

1. Lack of nitrogen can lead to stunted growth or to the yellow-red discoloration of leaves in green vegetables, e.g. cabbage;

2. Lack of potash can bring about poor fruit development and abnormal ripening;

3. Calcium-moisture imbalance can cause blossom-end rot in tomatoes and bitter pit in apples;

4. Boron deficiency can lead to hollow stem in cabbage and cauliflower;.

5. These are a few of the commoner soil-nutrition problems that can be readily identified at harvest.

6. The problem of fertilizer balance in soils and its effect on crops is complex and depends also on other conditions such as temperature, moisture, acidity of the soil and reactions among different fertilizer chemicals.

7. Severe soil-nutrition problems need reference to specialist advice, if available.

Pre-harvest influences on post-harvest performance

The overall quality and condition of fresh produce cannot be improved after harvest.

The final potential market value of his produce depends on the grower's decisions on what and when to plant and on the subsequent cultivating and harvesting practices.

Growers in general rely on their own experience and local traditions in selecting crops and in cultivation practices, but if they want or need assistance they may need to be referred to agricultural extension officers or possibly to research and development specialists.

Influence of production practices

Pre-harvest production practices may seriously affect post-harvest returns in quality and quantity and result in the rejection or downgrading of produce at the time of sale. Some of them are:

Water supply (Irrigation). Growing plants need a continuous water supply for both photosynthesis and.

Bad effects can be caused by:

I. Too much rain or irrigation, which can lead to brittle and easily damaged leafy vegetables and to increased tendency to decay;

II. lack of rain or irrigation, which can lead to low juice content and thick skin in citrus fruit;

III. Dry conditions followed by rain or irrigation, which can give rise to growth cracks or secondary growth in potatoes or to growth cracks in tomatoes.

Influence of production practicesCultivation practices.

Good crop husbandry is important in achieving good yields and quality of fresh produce. Certain aspects are particularly important, such as:

1) Weed control-weeds are commonly alternate or alternative hosts for crop diseases and pests, and those growing in fallow land near crops are as important as those growing among the crop. Weeds also compete with crops for nutrients and soil moisture;

2) Crop hygiene-decaying plant residues, dead wood, and decaying or mummified fruit are all reservoirs of infection causing post-harvest decay. Their collection and removal are crucial factors in the reduction of post-harvest losses.

The importance of post-harvest losses

1. Time and money are required to cultivate food products, and unless the farmer is providing food only for his own household, he automatically becomes part of the market economy: he must sell his produce, he must recover his costs, and he must make a profit.

2. Estimates of the post-harvest losses of food grains in the developing world from mishandling, spoilage and pest infestation are put at 25 percent.

3. Fruit, vegetables and root crops are much less hardy and are mostly quickly perishable, and if care is not taken in their harvesting, handling and transport, they will soon decay and become unfit for human consumption.

4. Estimates of production losses in developing countries are hard to judge, but some authorities put losses of , tomatoes, bananas and citrus fruit sometimes as high as 5O percent.

Causes of losses vary widely

I. Factors affecting post-harvest food losses of perishables vary widely from place to place and become more and more complex as systems of marketing become more complex.

II. A farmer who is growing fruit for his family's consumption probably doesn't mind if his produce has a few blemishes and bruises.

III. If he is producing for a market at any distance from his own locality, however, he and his workers, if he has any, must have a different attitude if he hopes to get the best money return on his work.

Loss assessment

1. There are no generally accepted methods for evaluating post-harvest losses of fresh produce.

2. In the appraisal of an existing marketing operation, the accurate evaluation of losses occurring is a problem.

3. It may be suspected that losses are too great, but there may be no figures to support this view because:

4. Records do not exist;

5. Records if available do not cover a long enough period of time;

6. The figures available are only estimates made by several observers;

7. Records may not truly represent a continuing situation; for example, losses may have been calculated only when unusually high or low;

8. Loss figures may be deliberately over- or understated for commercial or other reasons in order to gain benefits or to avoid embarrassment.

9. It is evident that the grower who wants to reduce his post-harvest losses must maintain reliable records.

Pre and Post Harvest Losses in a Glimpse

In fruits and vegetables the quality of produce starts deteriorating right after their harvest. Primary factors responsible for post‑harvest produce losses are:

poor pre‑harvest measures

1. Adoption of poor production techniques (varieties with low shelf life, imbalance use of nutrients,

2. Insect pest and disease infestation and abiotic stresses;

3. Low tech harvesting procedures–

4. Non‑application of pre‑harvest recommended treatments/practices,

5. Harvesting at improper stage and improper care at harvest;

Post‑harvest problems

6. Non‑removal of field heat,

7. Dumping produce,

8. Moisture condensation causing pathogen infestation,

9. Packaging in bulck with out sorting and grading of produce, improper transportation and storage,

5. Distant and time consuming market distribution

What are the principal causes of losses?

1. All fruits, vegetables and root crops are living plant parts containing 65 to 95 percent water, and they continue their living processes after harvest.

2. Their post-harvest life depends on the rate at which they use up their stored food reserves and their rate of water loss.

3. When food and water reserves are exhausted, the produce dies and decays.

4. Anything that increases the rate of this process may make the produce inedible before it can be used.

5. The principal causes of loss are discussed , but in the marketing of fresh produce they all interact, and the effects of all are influenced by external conditions such as temperature and relative humidity.

1.Physiological deteriorationa) An increase in the rate of loss because of normal

physiological changes is caused by conditions that increase the rate of natural deterioration, such as

b) High temperature,

c) Low atmospheric humidity

d) Physical injury.

e) Abnormal physiological deterioration occurs when fresh produce is subjected to extremes of temperature, of atmospheric modification or of contamination.

f) This may cause unpalatable flavors, failure to ripen or other changes in the living processes of the produce, making it unfit for use.

2.Mechanical damage (physical injury)

1) Careless handling of fresh produce causes internal bruising.

2) Which results in abnormal physiological damage or splitting and skin breaks, thus rapidly increasing water loss and the rate of normal physiological breakdown.

3) Skin breaks also provide sites for infection by disease organisms causing decay.

Mechanical injury also depends

Mechanical injury. The high moisture content and soft texture of fruit, vegetables and root crops make them susceptible to mechanical injury, which can occur at any stage from production to retail marketing because of:

a) Poor harvesting practices;

b) Unsuitable field or marketing containers and crates, which may have splintered wood, sharp edges, poor nailing or stapling;

c) Over packing or under packing of field or marketing containers;

d) Careless handling, such as dropping or throwing or walking on produce and packed containers during the process of grading, transport or marketing.

e) Injuries caused can take many forms:

Injuries caused can take many forms

1. splitting of fruits or roots and tubers from the impact when they are dropped;

2. internal bruising, not visible externally, caused by impact;

3. superficial grazing or scratches affecting the skins and outer layer of cells;

4. crushing of leafy vegetables and other soft produce.

Injuries cutting through or scraping away the outer skin of produce will.

a. Provide entry points for moulds and bacteria causing decay.

b. Increase water loss from the damaged area.

c. Cause an increase in respiration rate and thus heat production.

d. Bruising injuries, which leave the skin intact and may not be visible externally cause.

e. Increased respiration rate and heat production.

f. Internal discoloration because of damaged tissues.

g. off-flavours because of abnormal physiological reactions in damaged parts.

Injuries from temperature

1. Injuries from temperature effects. All fresh produce is subject to damage when exposed to extremes of temperature. Commodities vary considerably in their temperature tolerance. Their levels of tolerance to low temperatures are of great importance where cool storage is concerned:

2. Freezing injury-all produce is subject to freezing at temperatures between 0 and -2 degrees Celsius. Frozen produce has a water-soaked or glassy appearance. Although a few commodities are tolerant of slight freezing, it is advisable to avoid such temperatures because subsequent storage life is short. Produce which has recovered from freezing is highly susceptible to decay.

3. Chilling injury- some types of fresh produce are susceptible to injury at low but non-freezing temperatures. Such crops are mostly of tropical or subtropical origin, but a few temperate crops may be affected

3.Diseases and pests

a. All living material is subject to attack by parasites.

b. Fresh produce can become infected before or after harvest by diseases widespread in the air, soil and water.

c. Some diseases are able to penetrate the unbroken skin of produce; others require an injury in order to cause infection.

d. Damage so produced is probably the major cause of loss of fresh produce.

e. The influences of all three causes are strongly affected by the various stages of post-harvest operations, which are discussed .

f. Furthermore, they all have great effect on the marketability of the produce and the price paid for it.

Post-harvest diseases can also be spread by.

1. Field boxes contaminated by soil or decaying produce or both;

2. Contaminated water used to wash produce before packing;

3. Decaying rejected produce left lying around packing houses;

4. Contaminating healthy produce in packages.

5. Pests. Although relatively few post-harvest losses of fresh produce are caused by attacks of insects or other animals, localized attacks by these pests may be serious.

6. Insect damage is usually caused by insect larvae burrowing through produce, e.g. fruit fly, sweet potato weevil, potato tuber moth. Infestation usually occurs before harvest.

7. Post-harvest spread is a problem where produce is held in store or is exposed to lengthy periods of transport.

8. Rats, mice and other animal pests again are sometimes a problem when produce is stored on the farm.

4. Influence of rootstocks on postharvest quality of some apples

i. Studies carried out at Deciduous Fruit Development Centre, Sariab, Quetta revealed that on rootstock MM 106, apple cultivars (Red Delicious, Golden Delicious, Star King Delicious ) showed better performance than on M‑9 rootstock for fruit texture and soluble solids.

ii. On the basis of organoleptic evaluation or consumers 'acceptability' MM‑106 showed partially better performance than M‑9. For skin Colour of fruit, rootstock M‑9 showed better results over MM‑106.

iii. However, rootstock MM-106 should better performance in terms of fruits texture, total soluble solid contents and consumers 'acceptability over M-9 rootstock.

Studies on potato storageThereafter, potatoes are mostly stored in the field in ordinary storage structures, where weight loss, rotting and sprouting of tubers deteriorate the quality of produce.

In cold storage the produce is held at 4-5oC.

At this temperature starch is converted to sugar and therefore potatoes become sweet.

Also, because of high charges of electricity this costs much higher as compared to ordinary storage conditions or storage of potatoes at relatively higher temperature

Studies on potato storage contd1. Improved low cost on-farm storage structure (where hot air is replaced by cool air during night using electric fan) the inside temperature was observed 3-4oC low and the stored potatoes retained marketable quality up to 90 days.

2. The sprout suppressant, "Camptothecin" when applied (sprayed) @ 0.5 % inhibited sprouting of tubers upto 45 days at 39oC, whereas in untreated control sprouting started after 30 days at 39oC.

3 Quality of potato tubers when held at 5oC or 9oC and 90% RH was retained until 60 days as the weight loss, rotting, sprouting and sweetening were checked.

Studies on tomato and other fruit storage

In case of tomato, dipped in 4% CaCl2 solution and kept at 15oC maintained marketable quality up to 16 days.

Studies on olive preservation

Olive fruit when preserved using 15% NaCl solution was found successful.

Quality preservation of apricots

Apricots when dipped @ 3% solution of potassium meta bisulphite for 3 hours and then dried proved to be successful.

Radiation effects on extending shelf life of some fruits and vegetables

Nuclear Institute for Food and Agriculture (NIFA), Peshawar demonstrated inhibitory effects on sprouting of onions and potatoes during storage; delay in ripening in banana, guava, mangoes, pears, tomatoes and persimmon; rot control in oranges and improvement in quality of mature green peaches by using safe levels of Gama radiations.

Bulb onions and garlic

Onions and garlic of different types are grown worldwide for the flavour they contribute to food. They are also commonly regarded as having medicinal properties. In many countries onions are used in the immature green state. In others, where the crop is seasonal, cultivars which produce bulbs that can be stored in a dry state are grown.

Maturity for harvesting

When the bulbs developing from the leaf bases of both garlic and onions are fully formed, the leafy green tops begin to yellow and eventually collapse at a point a little above the top of the bulb, leaving an upright short neck. When the tops "go down" in this way, the bulbs are ready for harvesting. Because all the onions or garlic in a crop do not mature at the same time, large-scale commercial growers harvest them when about half the tops have gone down.

Small-scale growers can, if they wish, harvest their crops progressively as the tops go down, especially so if they intend to store the dry onions for sale or use at a later date.

Agricultural chemicals. These are of two types:

Pesticides and herbicides are used as sprays or soil applications to control weeds, disease and insect pests.

1) They are dangerous because they can damage produce by producing spray burns if used incorrectly, and they can leave poisonous residues on produce after harvest.

2) In most countries there are laws to control the use of pesticides, which should be used only in recommended concentrations.

3) Strict observance of the recommended delay between the last spraying and the harvesting is required in order to keep poisonous spray residues from reaching the consumer.

4) Advice on regulations should come from extension or other agricultural department officers.

5) Growth-regulating chemicals are used in the field mainly to improve the marketability of fruit in order to control the time of fruit set and to promote uniform ripening.

6) They are of little importance to small-scale production.

7) Their effective use requires specialist knowledge, and they are mainly applicable to large-scale commercial production.

8)

When is fresh produce to harvest?

1. A critical time for growers of fruit and vegetables is the period of decision on when to harvest a crop.

2. Normally any type of fresh produce is ready for harvest when it has developed to the ideal condition for consumption.

3. This condition is usually referred to as harvest maturity.

4. Confusion may arise because of the word maturity since, in the botanical sense, this refers to the time when the plant has completed its active growth (vegetative growth) and arrived at the stage of flowering and seed production (physiological maturity).

How is harvest maturity identified? Most growers decide when to harvest by looking and sampling. Judgements are based on:

1. Sight-colour, size and shape

2. Touch-texture, hardness or softness

3. Smell-odour or aroma

4. Taste-sweetness, sourness, bitterness

5. Resonance-sound when tapped.

6. Experience is the best guide for this kind of assessment.

7. Newcomers to fresh produce-growing may find that learning takes time.

8. Harvest maturity can readily be observed in some crops: bulb onions when their green tops collapse and potatoes when the green tops die off. Other crops can be more difficult: avocados remain unripe off the tree after maturity.

Selection of varieties for better shelf life

Vegetable varieties:

1. Roma (tomato),

2. NARC ‑ 91 (onion),

3. Medium Long Green (chillies),

4. Local Selections (cucumber)

5. Meteor (pea) have shown better transportation quality and longer shelf life.

In fruits; varieties:

a) Dhaki (date palm),

b) Cardinal, Flame Seedless (grapes)

c) Local Selections (fig),

d) Tarnab gulabi (pomegranate)

e) ARS (N) Mingora No. 7, No. 8 & No. 9 (peach) were found high yielding with longer post‑harvest life.

Training WorkersI. Training workers. This training should cover general aspects of produce-handling

for all workers and specific training for those engaged in tasks requiring greater skill.

II. General training. For everyone concerned with harvesting and field handling, general training should include:

III. Demonstrations of the causes and effects of damage to produce, emphasizing the need for careful handling at all times to avoid mechanical injuries from such causes as:

IV. Wooden containers with rough edges, splinters, protruding nails or staples;

V. Overpacking containers which are to be stacked;

VI. Damaging produce with long fingernails or jewellery;

VII. Dropping or throwing into containers at a distance;

VIII. Throwing, dropping or rough handling of field containers.

IX. An explanation of the need to avoid the contamination of harvested produce from such causes as:

X. Placing the produce directly on to the soil, especially wet soil;

XI. Using dirty harvesting or field containers contaminated with soil, crop residues or decaying produce: containers must be kept clean;

XII. Contact with oil, gasoline, or any chemicals other than those used specifically for authorized post-harvest treatments.

Specific training1) Specific training. Workers allocated to specialized tasks, such as

crop selection and harvesting, and the post-harvest selection, grading and packing (if applicable) of the crop should be given specific training. This will include demonstration and explanation of:

2) the methods of evaluating the readiness of the crop for harvest, and the rejection of unsuitable produce at harvest, according to market requirements;

3) the actual technique to be employed in harvesting produce, e.g. breaking the stem or plucking, clipping, cutting or digging;

4) the use of harvest containers, and the transfer of produce to field or marketing containers;

5) the selection of marketable produce at the field assembly point and (if applicable) grading for size and quality;

6) the correct application of post-harvest treatment (where produce is to be packed on the farm directly into marketing packages), e.g. fungicides, wax coating;

7) the method of packing market packages or other containers.

Storing and Grading

1. Sorting and grading are pre-requisite for appropriate packaging and market distribution. Low cost energy efficient on‑farm storage structures are to be introduced on extensive scale. Packaging has to be cost effective.

2. Dehydration of vegetables and fruits is to be introduced as cottage industry. Preservation and processing of vegetables and fruits both at semi- commercial and commercial scale needs to be carried out.

3. The aforementioned items would ensure optimum return to growers and traders. Better produce handling and management would ensure regular market supply and the consumers will enjoy the affordable prices.

4. This will also help promoting export of high value perishable commodities to other countries.

5. A well coordinated R&D programme on produce handling and marketing at national level is, therefore, essentially required.

Assistance to small farmers

Since small farmers produce most of the fruit and vegetables grown in developing countries, any Programme to improve marketing must include plans to upgrade their activities. Efforts directed to this end will be consistent with national development policies as most countries give high priority to improving the economic status and quality of life of the small farmer.

1. Problems to confront. Rapid economic development of small farmers is not easy to achieve. Their status is characterized by:

2. Small landholdings, usually less than I ha, with occupancy as a tenant or share-cropper with uncertain tenancy rights;

3. Lack of access to markets because of inadequate roads or transport;

4. Haphazard choice of crops; careless preparation of produce for market;

5. Unawareness of post-harvest technologies and facilities;

6. Forced dependence on a restricted trading environment;

7. Lack of control over pricing;

8. Lack of marketing extension services;

9. Insufficient resources to change marketing practices.

10. These are some of the obstacles to general development and must be addressed before small farmers can enter the economic mainstream of a developing country.

THE BASICS OF POSTHARVEST TECHNOLOGYThe three main objectives of applying postharvest technology to

harvested fruits and vegetables are:

1. To maintain quality (appearance, texture, flavor and nutritive value)

2. To protect food safety, and

3. To reduce losses (both physical and in market value) between harvest and consumption.

4. Effective management during the postharvest period, rather than the level of sophistication of any given technology, is the key in reaching the desired objectives.

5. While large scale operations may benefit from investing in costly handling machinery and high-tech postharvest treatments, often these options are not practical for small-scale handlers.

6. Instead, simple, low cost technologies often can be more appropriate for small volume, limited resource commercial operations, farmers involved in direct marketing, as well as for suppliers to exporters in developing countries.

Local Condition of Small farmers

1. Local conditions for small-scale handlers may include

2. labor surpluses,

3. lack of credit for investments in postharvest technology,

4. unreliable electric power supply,

5. lack of transport options,

6. Lack of storage facilities and/or packaging materials,

7. as well as a host of other constraints.

Fortunately, there is a wide range of simple postharvest technologies from which to choose, and many practices have the potential of meeting the special needs of small-scale food handlers and marketers.

Many simple practices have successfully been used to reduce losses and maintain produce quality of horticultural crops in various parts of the world for many years.

Steps in Post Harvesting There are many interacting steps involved in any postharvest system. Produce is often handled by many different people, transported and stored repeatedly between harvest and consumption. While particular practices and the sequence of operations will vary for each crop, there is a general series of steps in postharvest handling systems that are often followed.

A. Harvesting and preparation for market

B. Curing root, tuber and bulb crops

C. Packinghouse operations

D. Packing and packaging materials

E. Decay and insect control

F. Temperature and relative humidity control

G. Storage of horticultural crops

H. Transportation of horticultural crops

I. Handling at destination