Food loss prevention in perishable crops - I. Rationale and directions for reducing food losses in perishable crops

Securing an adequate food supply has been the fundamental concern of mankind over the millenia, and even in today's mode m world of great scientific and technological achievements, diets are inadequate for about five hundred million people. In the community of nations concern is increasingly focused on fulfilling the basic needs of all people, and the need for food is a dominant one. Without ensuring satisfactory diets, people cannot lead healthy and productive lives.

Agriculture, including fisheries, is the main if not the sole provider of food and the crucial question can be raised if and how far agriculture can respond to the rising demand for food in the gaming decennia.

A recent study (FAO) referring to 90 developing countries representing 98% of the population in the developing world (excluding China) reveals that the most striking share of increases in food demand will be caused by expanding world population. By the year 2000 fifty per cent more food will have to be available to meet present intake levels; yet additional food supplies will be needed by the end of the century to conquer famine and malnutrition. With respect to the material production inputs, which include land, water, minerals, organic substances, and energy, to meet these production targets, the availability of land will be the most limiting factor. Consequently, between 1980 and 2000 only twenty-eight per cent of the required additional crop production will be derived from area expansion and seventy-two will have to come from yield increases and more intensive cropping. This, in turn, will put more than proportional demands on water, fertilizer, pesticides, energy and managerial skills.

These figures and trends may illustrate that the case to reduce postharvest losses, or preserving what has been produced with increasing efforts and costs, has became much stranger and will became more so in the future.

Attention to the concept of post-harvest food loss reduction as a significant means to increase food availability was drawn by the World Food Conference held in Rome in 1974. The 7th Special Session of the U.N. General Assembly in 1975 passed a Resolution calling for a 50 per cent reduction of post-harvest losses by 1985. This recognition of the potential value of post-harvest loss reduction has found practical expression in the continuing debate among a number of International Organizations and Institutions. As a result several initiatives at the international level have been taken with the special aim of making a concerted effort to reduce unnecessary losses at all the post-harvest stages of the food production process. In FAO, after consultation with its Governing bodies, food foes prevention became a priority area and an Action Programme became operational in early 1978. The United Nations Environment Programme supports and promotes ecologically sound and sustainable development. Food loss reduction is an important activity in which UNEP has an interest, because this will increase the resource base as well as enhance the environment.

The FAO Action Programme so far has focused only on staple foods with particular emphasis on food grains, in order to make the greatest possible impact with limited resources. This should, however, not detract from other important foods where losses are known to exist in the post-harvest system. It was felt that a stage had been reached where a second large group of commodities, the perishable crops, which for reasons of their importance to human nutrition, their magnitude of production and their vulnerability to oilage have common characteristics and problems, should be investigated further.

To this end the United Nations Environment Programme and FAO organized an Expert Consultation on the subject. Preceding this meeting three Consultants with different background and geographical expertise visited major Centres of activities in this field and prepared three working documents.

For the Consultation itself another 15 Specialists from the various post-harvest disciplines and with a broad geographical coverage were invited. me 4-day meeting took place in May 1980 at FAO Headquarters in Rome. m e complete list of people attending, or having assisted in the preparation of this Consultation, is given on Pages xvii-xix. m e major task of the

Meeting was to discuss and complement the information prepared by the Consultants on the present status of the post-harvest food losses occurring in perishable crops and the opportunities and means to reduce these losses.

The conclusions reached by the meeting were:

Post-harvest loss in perishable crops constitutes an important issue that needs increased and continuing attention at national, regional and international levels by FAO, Governments and other concerned organizations because it requires fewer resources and applies less pressure to the environment in maintaining the quantity and quality of food than through increased production to offset post-harvest losses.
Traditional effective methods for preventing and reducing Postharvest losses need to be identified and exploited; this includes maintenance of continuous supply, storage for restricted periods, and transformation to durable products.
Some valuable traditional technologies for food Preservation are in danger of becoming lost because they are being superseded by more sophisticated methods of doubtful long-term value. Modern and technology-intensive methods should be applied appropriately according to prevailing conditions including cultural factors. Efficient and proper management of such technologies is as important as the types of equipment and facilities selected.
The entire food production and supply system needs to be addressed as a whole, because of the interrelationship between and amongst the different components of the system. A substantial amount of post-harvest losses have their origin in the pre-harvest stage, for example, genetic factors, infections, pest infestations, environmental factors and cultural practices during the production stage.
Most post-harvest losses in horticultural produce result from infection by fungi and bacteria (pre- or post-harvest), and from inherent physiological activity although insects, rodents, nematodes, and occasionally birds may cause significant losses under certain conditions Insects can disseminate some plant pathogens and also provide wounds as points of entry for microorganisms. In general, pre-harvest application of fungicides is more important in the control of post-harvest problems of fruit and vegetable crops than in root crops. Infections established prior to harvest are extremely difficult to control after harvest. Sanitation in all post-harvest operations is a key factor in eliminating sources of infection and reducing levels of contamination.
A distinction needs to be made between post-harvest losses incurred as a result of inadequate production planning (surpluses), speculation or excessive quality grading (mostly occurring in developed countries) and losses incurred due to lack of know-how, technology, or infrastructure (mostly occurring in developing countries) because the reduction of the different types of losses requires different approaches.
All food losses occur a particular socio-cultural and economic environment. Techniques to reduce food losses require cultural and economic adaptations. While physical aspects are clearly mast important, the subject must be considered within the wider framework of an approach whereby human as well as physical factors are taken into account.
Since losses are commodity and location specific, there is a need for specific activities, e.g., workshops, pilot projects, training courses, marketing studies, etc., in each country or region to address the priority problems of that area. Particular attention needs to be given to locally important commodities in each area. International assistance to developing countries in the field of post-harvest loss prevention needs to be geared to improve capability of the developing country to handle these programmes.
There is a need for an international information network to promote exchange of information on prevention of losses in perishable crops. Links between existing national and international institutions need to be strengthened. There is a need for a periodically annotated bibliography covering studies on post-harvest food losses in perishable commodities and for a world-wide directory of post-harvest technology centres and personnel.
There is a need to establish exchange programmes (technical co-operation between developing countries) between countries of similar needs and interests but which have an apparent difference in advancement in post-harvest handling systems.
Proper management of temperature and humidity of root crops and certain other perishables in the initial post-harvest period is essential to good curing which improves wound healing and minimizes infection by microorganisms.
Refrigeration is an important tool in the temperature management of perishables. It is desirable to remove field heat as soon as possible after harvest and to store at that temperature which will give the longest shelf-life. However, refrigeration technology should not be adopted as a panacea for all problems connected with deterioration associated with high temperature. Its introduction needs careful study, due consideration of its appropriateness and of the supporting infrastructure available within the post-harvest system, as well as the relation of refrigerated storage capacity to the collection, pre-cooling, transportation, marketing and distribution system. Special care may be needed when a complete "cold chain" cannot be maintained within this system, and where refrigerated storage would form an additional operation in post-harvest handling.
A key factor influencing the magnitude of post-harvest losses is the severity of mechanical damage to the crop during harvest and subsequent handling because it provides pathways for invasion by fungi and bacteria.
Intervention activities need to be particularly directed to those individuals involved in handling the commodity throughout the post-harvest system and consideration needs to be given to their level of understanding.
Any innovation to reduce post-harvest losses introduced to the private sector should be accompanied by a clear financial incentive.
In exploring new technologies, due attention needs to be paid to ensuring their acceptance by producers and market operatives, particularly if the adoption of a new technology would mean the displacement of labour or a particular class of labour (e.g., women).
In view of the very short post-harvest storage life of cassava, research work on fresh cassava should continue but priority should be placed on research related to its transformation into stable products. Gari and cassava flour are examples of such transformed products.
In the case of yam, parallel work is necessary on the fresh product as well as on the transformed forms but with major emphasis on storage of the fresh product.
Processing or transformation of perishable crops could form a rural agro-industrial operation and assist in retaining the added value of processing in rural areas.
Additional research effort is needed in some areas where basic knowledge is inadequate, for example, chilling damage to tropical fruits and vegetables, the causes of deterioration of cassava, dormancy of yams, post-harvest physiology and pathology of roots and tubers, genetic improvement techniques, biological nest control, the effect on storability of chemicals and cultural practices used during the growing period. This will require the training and employment of specialized post-harvest technologists concerned with perishable crops.
Based on presently available information, the use of post-harvest chemicals has not shown toxicological problems. But when they are used there is need to ensure that the dosages and residues conform with internationally recommended maximum levels, e.g., of the FAO/WHO Codex Alimentarius Commission.
The preparation of outlines on when, where and why losses occur in selected perishable food crops is desirable but it is recognized that preparing a full methodology for loss assessment on perishables of plant origin is a complicated and time-consuming task. Diagnostic studies using an interdisciplinary approach are needed to properly identify the area where losses occur within the post-harvest system of perishable food crops.
There are some important issues that lie outside the immediate scope of this Expert Consultation that warrant further attention, for example, preventing the possible carryover of excessive field pesticides into the postharvest system, agricultural chemicals that have been banned in the country of origin but nevertheless still exported, grades and quality standards for horticultural products, reduction of losses in household food preparation, and increased consideration of environmental aspects in post-harvest intervention activities related to cereals and other foods.

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