Agriculture for Engineers 4 (3+1)

Lesson 44. Harvesting, Grading and Packaging

44.1 HARVESTING 

Different kinds of fruits need different methods of harvesting. Some fruits are easily pulled, although there is possibility of tearing off a piece of flesh and/or ding. Some fruits are harvested with stalk with aid of clipper or shear, where the stalk may be source of damage especially during packaging. Fruits at higher branches are harvested with long a hold with a bag (mango). Fruits may be caught as it fall using mechanical harvesters. The best means of reaching high fruits is with a ladder. In banana the trunk is cut with a sickle over half way through and then the bunch is cut. About 30 cm. of the stalk must be left to make the handling easy. Citrus fruits are very much susceptible to damage while harvesting. During wet and humid condition the rind will be turgid and liable to bruising or tear-off rind is common if the fruits are pulled. The post harvest quality and storage life of fruits are controlled by maturity. Vegetables are harvested as and when they attain maximum size and yet are tender. Over Maturity in root crops causes sponginess and pithiness. Delay in harvesting of onion and garlic reduces their storage quality.

44.1.1 When to Harvest Horticulture Crops?

• During cooler part of the day (in morning).
• Do not harvest in hot period, cause wilting and shriveling.
• Harvesting during rains or immediately after rains should not be carried out.                    

Citrus fruit become susceptible to damage if harvested during rains, as their rind becomes turgid and prone to easy bruising sunscald.

No any bruising or injurious during harvesting may later manifest as black or brown patches, e.g. Latex coming out of stem in mango should not be allowed to fall on fruits as creates a black spot.

  44.1.2 Post Harvest Handling

Care in harvesting and handling is necessary to preserve subsequent quality of fruits and vegetables, faulty harvesting and rough handling at the farm directly affect market quality. Oil gummosis is common peel injury of citrus fruits (causing extensive losses) which mostly occurs at harvest, if not done carefully. Mechanical injury to the rind forces the oil out of the epidermal oil glands, which kills adjacent cells of the flavor and also causes soil spotting on the surface of adjacent undamaged fruit. When put together cells killed by oil are readily infected by fungi resulting in increased decay. Oil spotting can be reduced or eliminate by good handling practices.

1. Bruises and injurious later show up as brown and black patches (e.g. banana, bhindi) making the commodities unattractive and physiological disordered. Rough handling on produce is cumulative. Several small bruises on a tomato can produce an off-flavour for consumers
2. Entries to micro organism leading to rotting.
3. Respiration is increased markedly by damages and storage life is shortened. Lack of knowledge in harvesting and handling results in substantial lost of fruits and vegetables.

It is estimated that 20 to 30% of the fruits and vegetables produced is being wasted due to defective methods of picking, storage, and transport procedures in our country. The quality of fresh fruits and vegetables defoliated due to these faulty handling procedure. The climatic condition in our country also limits post handling life of there commodities Hence proper scientific method used to be allowed in harvesting and all the post harvesting operation of the fruits and vegetables to prevent the huge losses being occurred and to maintain the quality. Post harvest technology is simple term as”Field to Table”. Programme involving the science applied in providing the consumers with best quality of fruits and vegetables from the field.

Post harvest handling consists of the following procedures:

44.2 GRADING, SORTING & SIZING

Grading, sorting, and sizing are based on soundness, firmness, cleanliness, size, weight, colour, shape, maturity, diseases, insect damage and mechanical injury. They are grouped in size. This is an important procedure to be followed in post harvest handling, before packaging storage, transport or marketing to minimize loss and maintain quality.

• Additional operation:  Along with grading, certain additional operation which include washing, pre cooling, degreening, curing,  waxing, fungicidal and other chemical treatment are also essential preparatory steps to packaging , storage transportation and subsequent marketing, washing, improves appearance, remove dirt, soil, scale insect, sooty mould, fungicide and insecticide residues. Detergent are added to water for effectiveness washing. The excess of surface water is dried by blowing heated air.
• Pre-cooling:  Pre-cooling is done to remove field heat as high temperature is detrimental to the keeping quality of fruits and vegetables. General aims are to slow down the respiration minimize the susceptibility to micro organism and reduce water loss. Several methods used are (a) air -cooling, (b) hydro cooling- fungicides can be added in cooling water. (c) vacuums cooling- most rapid methods of pre cooling, especially, for leafy vegetables curing- certain vegetables like onion have to be cured after harvest before storage and transport marketing.
• Degreening: In certain cases development of ripe colour by degrading the green colours is induced usually by the treatment with ethylene under controlled temperature and humidity and O₂ and CO₂ concentration e.g. Banana, Mango, Citrus, Tomato.
• Waxing: (1) Waxing is done to reduce the evaporation loss of water from the fruits and vegetables thereby increasing the storage life. (2) It gives a fresh glossy appearance which improves the market value. (3)Recommended fungicides can be added to the wax to reduce the spoilage buy fungus. The wax replaces the natural protecting waxy layer which is removed by handling, washing, etc. CFTRI Mysore, has developed a wax emulsion (Waxol-123) for waxing of fruits and vegetables.

44.3 PACKAGING

Packaging is done for more efficient handling and marketing , greater appeal, more potential life. Packaging requirement vary with different fruits and vegetables. Packaging cannot improve quality. Hence only best possible produce should be packed. Inclusion of decayed or damaged produced in bulk or consumer packages may become a source of infection and reduce the sale at the market. Packaging is not a substitute for refrigeration; packaging combined with refrigeration is the best methods. A good package is aim to protection of product from physical. Physiological and pathological deterioration   causes throughout storage, transport and market.

Benefits of packaging:- serves as an efficient handling units, serves as a good storage unit, protect quality and reduce waste, protect from mechanical damage and moisture loss, provide beneficial modified atmosphere, prevent pilferage, provides service and sales motivation.

Material for packaging:-wooden boxes, bamboo basket are the conventional packs. Fibre board cartoons, corrugated card boards, and several flexible plastic packaging. Materials used for packing material are (1) polyethylene (low density)-most widely used for consumer packaging ,strong considerably moisture proof , resistant to several chemicals and cheap (2) polyprophlene (3)polyvinyl chloride film (4) cellophane (5) polifilm. The emphasis is being made now to use those materials which contains less or no wood for packaging as our forest resources being exhausted fastly and is at a precarious condition.

Consumer packaging with plastic:- the original function of packaging was to contain carry and dispence products. However the use of plastic as packaging materials has allowed so much variation and versatility as to protect ,presence, process, store, measure, communicate, and display of products. Fruits and vegetables are packaged in smaller quantities in polyethylene pouches as consumer packages. In these films proper ventilation is needed to prevent moisture accumulation. Leading to rotting of  the content and to relegate O₂ and CO₂ concentration inside pack. High CO₂ concentration may cause deterioration in quality of the content. Congenial modified atmosphere inside the pack would increases the storage life of the contents.

• Pre Packaging: Pre packaging increases the shelf life by creating modified atmosphere with an increase in concentration of CO₂ in package. L.D.P.E. films have high O₂ and CO₂ transmission rates are more durable.
• The pouch used reducing bruising facilitates inspection, reduces moisture losses and prevent dehydration. In pre packaging leaves stalk stem are washed cleaned and weight quantities are put in pouches.
• Ethylene absorbents hydrate lime may insert in packages to retard ripening process.
• A wide range of packages like gunny bags, bamboo ,woven ,grass stem basket, wooden cares, earthen pots, corrugated fibre board cartoons and rigid plastic carats are used.
• Wheat and paddy straws, banana leaves, dry grass are used as cushioning material.

 44.4 STORAGE

Storage of fruits and vegetables prolongs their usefulness, it is also check market glut, provide wide selection of fruits and vegetables throughout the year, helps in orderly, marketing, increases profits to the producers and preserve the quality of the living products.

The principal aim of storage is to control rate of transpiration, respiration and disease infection and to preserve the commodity in its most usable form for consumers without proper storage, the following undesirable things may occur

1. Sprouting:- e.g. onion, ginger, garlic, potatoes etc.
2. Rooting:- e.g. sweet potato, onion etc.
3. Seed germination:-e.g. pod bearing vegetables, tomato, papaya etc.
4. Degreening:-e.g. potatoes of exposed to light, green portion contain solanin which is toxic.
5. Toughening: e.g. Green beans, bhindi etc.

44.4.1 Factors affecting storage:

i. Pre-harvested factors: climatic, cultural, and pathogenic

ii. Harvesting and handling practices: mechanical injuries

iii. Pre-cooling: an important factor prior to storage reduces P.L.W. and improves storage life.

iv. Cleanliness

v. Variety and stage of maturity at harvest - prematurely harvested mango, bananas, tomatoes will not ripe satisfactorily.

 44.4.2 Storage life:

   It may be prolonged by (a) proper control of post harvested diseases (b) chemical treatments (c) irradiation (d) refrigeration (e) controlled atmosphere storage.

a. Proper control of post harvest diseases:

Knowledge of the time and made of infection is essential for the development of an effective programme for diseases control. Fruits attached to the plant may be infected by direct penetration of a fungus through enticle by wounds or by natural openings. Many most harvested diseases are through injuries after harvest such as cut steams and mechanical damage to the surface in the course of handling and transporting

Cut-stem infection: e.g. crown root of banana hands, black-root of pineapple and stem end root of papaya and mango.

Post harvested diseases initiated in wound create during or after harvest may be controlled by fungicides treatment.  If application can be made before pathogen has penetrated deep into the fruits.

Low temperature reduces the severity of post harvest diseases by retarding ripening and also by retarding the growth of micro-organism

Humidity more than 90% favour the development of post harvest diseases. Plastic films of low permeability and without ventilation increases post harvest diseases.

Control of post harvest diseases – the basic principles are (1) prevention (2) cure (3) delaying the appearance of symptoms and (4) retarding diseases spread more than one approach is usually required for satisfactory diseases control.

b. Chemical treatments:

Growth regulators like GA, MH, CCC, ALAR, and other chemicals like acetylene gas ethylene gas are used to regulate ripening and storage life of fruit and vegetables.

Post harvest treatment with GA markedly retards ripening and tomatoes guava, bananas and mangoes.

Malik hydrazide (MH) a growth retardant inhibits spouting of onion, potato. Ethylene, acetylene are used to hasten ripening in fruits.

c. Irradiation:

Low radiant dosage is applied to fresh fruits and vegetables to prolong their storage life. Irradiation can delay the ripening destruction of spoilage micro-organism and disinfection. It has been used successfully in retarding the sprouting of potatoes, sweet potatoes, onion. Irradiation is successful in control of fruit fly on citrus, mango seed, weevil control, papaya fruit fly control. For some fruit like mango, banana, papaya and additional advantage in the use of irradiation for disinfestations purpose is retardation of ripening. in several vegetables irradiation is not useful as it causes discoloration excessive softening, off flavour, increase decay etc.

Irradiation method is not cleared as safe to use for prolongation of shelf life of fruits and vegetables in India though its use in certain commodities like onion and potatoes is cleared in several other countries.

d. Refrigeration:

To date refrigeration is the only known economical methods for long term storage of fruits and vegetables, all the other methods of regulating ripening and deterioration are at best supplemental to refrigeration. Other methods are not worked satisfactory without refrigeration. Refrigeration requirements vary with different kinds of fruits and vegetables and their maturity stages which are standardized.

Optimum temperature for the even ripening and development of good flavor, and attractive colour of most fruits generally fall within a range of 59-79’ F. mangoes ripened at 68’F contains 20% as much sugar as these ripened at 95’F at storage temperature of about 75’F is optimum for the storage of most fruits except grapes, litchi, pomegranate, and apple which require a low temperature range 32 to 41’F. Leafy vegetables require 90% to 96% R.H. They should not be stored together with ripening fruits as ethylene is injurious to them.

Fruit and vegetables bean cucumbers, bhendi, sweet peeper, squash and tomatoes are sensitive to chilling at very low temperature. They are to be stored as 40 to 50’ F. Higher temperature cause toughening, yellowing and decay while low temperature cause pitting.

Chilling injury: A major problems in post harvest handling at low temperature which otherwise would prolong their storage life .chilling injury is a disorder induced by low, but non freezing temperature is susceptible fruits and vegetables.

(a) pitting- limes, mangoes, avocado.

(b) water-soaking – tomato

(c) smoky-appearance- banana

(d) surface discoloration- mango etc.

e. Controlled atmosphere storage:

Controlled atmosphere (CA) implies to addition or removal of gases, resulting in an atmospheric composition substantially different from normal air. CA storage is a system for holding produce in respect to the proportion of nitrogen (N₂), oxygen(O₂), or carbon dioxide (CO₂). Other gasses such as CO or ethylene are also added to the storage atmosphere. CA storage process could be the most important innovation in fruit and vegetables storage since the introduction of mechanism of refrigeration. This method, if combined with refrigeration markedly retards respiration activity and may delay softening yellowing, quality change etc.