4. Fruits and vegetables
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4.1 General considerations
Many post-harvest losses are direct results of factors before harvest. Fruit a and vegetables that are infected with pests and diseases, inappropriately irrigated and fertilized, or generally of poor quality before harvesting, can never be improved by post-harvest treatments. Very often the rate of commodity loss is faster if the quality at harvest is below standard. Thus, the processes in the attainment and maintenance of quality from production, harvesting, handling and marketing must be considered a unified system. The success of preserving the harvest-fresh quality of produce demands control of each step in the system, depends on the previous stop and therefore is a chain of interdependent activities.
The small size and isolation of many vegetable farms make it logical to employ manual harvest labour which is often relatively cheap and non-organized. Traditional methods of harvesting are still employed using a minimum of mechanical aide. Many of the farmers may know their market but do not analyze it and plant without much concern for it. Price considerations are usually given more weight than the quality of the produce. Early harvesting of carrots, chayote, snap beans, squash and bottle gourd give better quality, but lower yield. On the other hand, vegetables may be harvested before reaching prime quality if the prevailing market price is high duo to the scarcity of the product. Knowledge of maturity indices is often inadequate in moat instances visual indices being used. Therefore, more experienced farmers can deliver better quality products than those with less experience.
The deterioration of a product starts during the harvesting operation. The more carefully a product is handled, the slower the deterioration process during subsequent handling operations. However, the farmers mar be unaware or indifferent to the condition of the product after harvest, and harvesting procedures may thus be rather careless. The only constraint is to avoid external injury. Until farmers are convinced that careful handling will increase profits, it will be difficult to persuade them otherwise.
In many countries contract buying is practiced where the contractor takes charge of the harvesting and may exert strict supervision of the operation.
The general problems for each fruit and vegetable group are summarized in Table 10:
Table 10 - General problems for each fruit and vegetable group at each handling step
|Types of Fruits/Veg.
|Right stage of maturity
|Over-packing; improper container
|Rough handling; poor road conditions
|Chemical changes; shrivelling
|Over-ripening; shrivelling; browning
|Excessive moisture may lead to rotting
|Mechanical injury in sacks
|Sprouting; improper curing; shrivelling
|Tubers & Corms
|Mechanical injury in sacks
|Improper curing; sprouting & greening
|Sprouting; rotting; shrivelling weight loss
|Excessive wilting; rotting under high moisture conditions
|Unsuitable container size; mechanical injury
|Rough handling; high transit temperature
|Over-trimming; mixed sizes
|Wilting at low relative humidity; shrivelling
|Over-trimming; excessive wilting; bacterial soft rot
|High transit temperature
|Loose curd; insufficient wrapper leaves
|Yellowing of curds
|Loosening of curd; fading of colour
|Improper method of harvesting
|Breakages of tissues
|High transit temperature
|Elongation of existing structure
|Bruising and other mechanical injuries
|Improper conditions in sacks
|Shrivelling and sprouting
* Attacks by micro organisms can occur in all steps of the post-harvest system either directly or resulting indirectly from actions or conditions occurring in each of the steps.
In meet of the developing countries the world, harvesting methods are very simple. Picking poles, to which a hook or cutting knife is attached' are generally used. Fruit blemishes and injury are usually unavoidable. Quite often the fruits fall to the ground becoming subject to field infestation. Planning, preparation and organization in the harvesting operations are necessary. Suitable harvesting tools, hand gloves, containers and supplies are needed by the harvesters. The grower should exert strict supervision on the harvesting operation.
Grading is a thing that most farmers are loath to do until they are convinced it will bring them added revenues or increases the acceptance of their products. A farmer may separate different varieties if they are distinguishable, but consumers in the tropical countries usually are more price conscious than quality conscious. That is not to say that they are unmindful of the quality, but if good quality products are too highly priced, they are often willing to settle for a poorer quality product. With the variety of vegetables offered for sale, shore is usually no difficulty in Betting cheaper substitutes. Thus, initially, for local markets, grading should be limited to only what is necessary. Deformed fruits and those with splits, punctures and incipient rotting should be removed. If the market is conditioned to accepting sound fruit with harmless surface blemishes (e.g., russet, windscarring, or mite injury), it is well not to attempt to change the situation for the time being. The following are likely to occur in the absence of proper sorting and grading procedures:
Containerization is probably, the weakest aspect in the distribution chain of fruits and vegetables. In general, packaging materials of unsuitable quality, such as large sacks, rough wooden boxes, second-hand cartons, bamboo baskets, or rattan containers are liable to cause produce to suffer from bruising, crushing' and puncturing. The use of suitable containers alone will do much to maintain the quality of fruits and vegetables. Farmers often selected the cheapest and most readily available containers. For example, the use of bamboo baskets has several disadvantages. The sides are sharp and easily bruise the produce. They are too deep and without sufficient side reinforcement, thus causing the produce to be Jarred or compressed. Moreover, handlers tend to throw rather than lift the produce gently because of its weight. The use of wooden crates could solve many of the objections to the bamboo baskets. The main objection to a wooden crate.
To summarize, transport losses are due to the following:
In many developing countries wholesale markets, if any are integrated with retail markets. Ideally, wholesale markets should be separated from the retail ones. However, this is influenced by the structure of the marketing chain and the scale of the industry. Frequently wholesale markets are overcrowded, unsanitary and lack suitable facilities for display, storage, ripening, loading and unloading. A main contributory factor to loss of leafy vegetables is trimming at wholesale markets prior to delivery at retail stands. Examination of trimmings showed that wholesalers and retailers trimmed their produce mainly because of the presence of decaying portions of leaves, due to bacterial soft rot. Thus, prevention of rotting during transport and storage would result in substantial reduction for postharvest losses of leafy vegetables.
Storage of fresh fruits and vegetables prolongs their usefulness, checks market gluts, provides a wider selection of fruits and vegetables throughout the year, helps in orderly marketing and may increase the financial gain to the producer. Adequate storage may reduce subsequent losses, but cannot overcome pre-storage losses. Adequate storage involves proper regulation of temperature, humidity, air circulation, proper stacking pattern, regular inspection, and prompt produce disposal as soon as maximum storage life has been attained. The feasibility of the construction of cold storage facilities and the interest among farmers and handlers to utilize the cold stores would again depend upon the economics parameters of the project. One of the greatest impediments to preserving quality through refrigerated storage is the consumers' strong preference for freshly harvested produce and resistance to stored produce.
Information on the storage temperature and humidity requirements of fruits and vegetables and the length of time they can be kept without decline in market value is either inadequate or unknown to those who need the information. If a farmer is persuaded to store his produce in cold storage and the market value decreases due to inadequate knowledge of the proper utilization of cold storage, it is not only he who will become disillusioned, but his friends also will be convinced of the non-profitability of cold storage.
Lack of capital may also force farmers to ignore the use of cold storage, even when available and effectively managed. Many growers depend on almost daily sales for their income and hence may be forced to accept a lower price immediately, rather than to store their produce in the anticipation of a higher price. There is also the storage rental price which the farmer may not be willing to pay unless he is thoroughly convinced that he will not only recover his investment, but will also profit.
The retailer usually disposes of produce which has been damaged by factors occurring further back in the marketing chain. At this stage, deterioration of perishables has already progressed to such an extent that street vendors have little opportunity to prevent further losses, either through storage or other preventive measures, except by estimating their potential sale for the day and buying only the amount that can be disposed of.
In Malaysia, although fruits and vegetable are sold in the open market, retailers improvise beach umbrellas arranged side by aide to provide acceptable shade to the commodity during market days. After the market is over in the afternoon the umbrellas are folded and the market area is again an open space. This simple technique or similar ones could be adopted in other developing countries as a temporary measure to provide shade to the produce.
Miscellaneous losses are numerous. The moat important ones are:
4.2 Individual fruits and vegetables
The following notes highlight some of the major problems of the more important commodities in the fruit and vegetable group. They are, however, indicative rather than exhaustive.
Bananas and Plantains. Harvesting is generally a one-man operation which frequently results in bruising and abrasions of fruits causing accelerated ripening and consequent decay. Latex staining is prevalent during dehanding. Bunches or hands are often piles one on top of the other without proper protection and fingers are easily detached and oftentimes wasted during transport. This is particularly true of the very open, loose bunches of certain plantain cultivars. In container transport loosely packed hands suffer considerable damage, especially on rough roads. In transit ripening and decay are usually high, notably over long distances.
Mango. Fruits are usually harvested at the time of the day when maximum latex flow is favoured. Latex stain is allowed to dry on the peel, hence immediately reducing consumer acceptability during retail. The collapsibility of the non-rigid crates often used for transport further aggravates quality lose by compression and bruising. The inaccessibility of production area to roads causes serious delays in transport, in addition to a mixed-cargo typo of transport. Stacking in vehicles often does not provide for adequate ventilation. Loading and unloading operations are rather rough. Cold storage is not usually practised. Ripening is mainly aimed at improvement of the appearance for sales purposes and not for maintaining quality.
Papaya. Picking poles injure the fruit and there is a relatively high percentage of fruit dropping on the ground, causing breakage and bruising of ripe fruits. Peduncles are not usually trimmed hence injuring other fruit a within the pack. Rigid containers are not adequately linde, and within a single pack fruits of assorted sizes and maturity stages are often found. In bulk transport fruit e arc piled one on top of the other without any suitable padding materials. High percentage of decay, particularly anthracnose, is the main problem during ripening and in retail.
Citrus. Improper time of harvesting greatly enhances rind injury or oleocellosis. Leaving long stubs on fruit a injures other fruits within the pack. Containers used are large and overpacked, generally without sufficient ventilation. Containers are piled high with the bottom crates bearing the full weight of crates on top. Delays in transport due to poor roads often cause over-ripening or yellowing of the commodity. Poor storage conditions favour decay and physiological disorders such as chilling injury can also occur if cold stores are not wolf managed.
Grapes are attacked by Botrytis, Cladosporium and Alternaria during storage. However, if the storage temperature is strictly maintained between 0° and 2°C, fungal attack can be reduced to a minimum Other loss factors could be berry drop, bruises, injury, water loss, and cracking of berries. Selection of unsuitable container type for packaging of grapes may also lead to heavy transit losses. Transit delays, adverse weather conditions and improper type of carriages, e.g., steel wagons, particularly during hot months may further aggravate transit losses.
Tomato fruits are usually picked when fully ripe, and are therefore very susceptible to cracking, bruising, and consequently decay. Packaging containers often used are deep bamboo crates with insufficient aide reinforcements allowing jarring and compression during transport. Loading and unloading operations are very crude. Handlers tend to throw the pecks rather than lift them gently, on account of their weight. During retail sellers tend to pour the contents of the pack into another container, rather than transferring the fruit gently, thereby increasing bruise damage. Fruit a at the breaker stage are mixed with the fully ripe or three-quarters ripe fruits reducing the market value of the pack. Shrivelling percentage can be high since fruits are often exposed to the sun.
Onions. Insufficient grading is still existent. Spouted, injured and partly decayed bulbs are usually mixed with sound bulbs in a pack. The use of slatted wooden creates is advantageous, especially during transport. Mesh bags of 40-50 kg. capacity are also used. Sacks are thrown rather than lifted, on account of their weight. Packs are piled one on top of the other with no provision for adequate ventilation. Pre-harvest spraying with sprout inhibitors is seldom practised resulting in serious sprouting during storage.
Cabbage/Lettuce. Improper harvesting tools contribute greatly to damage to the produce in the form of out a and abrasions. Trimming of outer leaves is usually not practised. In container transport, large crates are used (50 kg. capacity). Bruising and tearing of the leaves is of common occurrence due to the sharp edges of the containers. Containers are piled one on top of the other with the bottom crates carrying the weight of the heads above. Bulk transport likewise results in higher losses.
Peas and Beans. Factors such as the method of packing, suitability of containers, mode of transport, distance covered, number of transshipments, handling, and storage facilities in the consuming centres, all contribute to the degree of loss reported.
4.3 Institutional aspects
The solution to the problems of improper handling of perishable produce in the tropics is rather difficult, owing to the complexity of the problem. It requires the solving of technical problems as well as those of credit, land, transportation and marketing availability. It also requires a change of people's attitudes to proposed solutions and new innovations. Such an approach can only be accomplished over the years, tackling specific problems in a stepwise fashion. There must be concerted efforts by the private and government sectors.
Extension work is needed to show that post-harvest procedures are as important as production techniques. It is not enough to produce good quality commodities through variety improvement and proper regulation of soil and climatic factors. The whole process from planting until the harvested products reach the consuming public must be a mutual undertaking between the growers and those who will handle the product after harvest. Post-harvest handling up to the final marketing stage must be considered as a single system. The success of maintaining the harvest-fresh quality of produce demands control) each atop depending upon the previous one. If the initial quality of the product is poor, no post-harvest treatment can improve it, although careful selection and grading may salvage some good quality produce from a mixed-quality sample. Thus handling procedures from harvesting until the product reaches the consumers are chains of interdependent activities.
The establishment of wholesale markets or cold storage facilities by Governments or other agencies must also meet the general approval of the persons who must use them. Of what use would a modern wholesale market be if the wholesalers would rather use an antiquated one that is more accessible to them? The establishment of a cold storage plant in an area accessible to the users must be accompanied by a sustained information and promotion campaign. Emphasis must be laid on the benefits of the farmer. Realistic rental rates and payments after the sale of product a could attract the farmer to use this facility. Above all' an essential prerequisite to the taking of a decision to erect a new wholesale market is the need to carry out a sound feasibility study to provide suitable information for the decision-making to use.
The establishment of co-operatives has done much in certain countries but only whore the organizations are effectively run and the members are aware of their responsibilities as well as the benefits. The farmers involved in cooperatives have a greater bargaining power and control of the production planning and marketing which may spur then can to improve or maintain the quality of their produce. They may also be encouraged to obtain credit.
Technical knowledge of post-harvest handling has been increasing and there is a need to translate this body of knowledge into systems and techniques that the farmer can understand and use. Agricultural extension information must be reliable. The extension worker must have a, good grasp of his job and must know where to turn when he cannot solve problem himself.
A continuing problem is the low educational lover of farmers in developing countries and their skepticism towards new methods they have never tried or seen before. Farming, especially of fruits and vegetables, is not looked upon as an attractive occupation. Often farming is an occupation of last resort. Vagaries of weather make farming a risky business and knowledgeable and enterprising farmers are few.
In a way, acceptance of improvements and innovation are tied up with the economic progress of a nation. If the buying power of the people is increased, they are more willing to accept the increase in prices associated with the improvement in the post-harvest handling of fruits and vegetables.
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