Research and technology Knowledge

Posted June 1996

Post-harvest technology and food quality

Science and technology for sustainable development, Part 6


Part 1
Forest management and conservation

Part 2
Land and water development

Part 3
Protecting fisheries resources

Part 4
Plant protection and pesticides

Part 5
Sustaining small farm enterprises

Part 6
Post-harvest technology and food quality

Part 7

Part 8
Plant production

Too much of the world's food harvest is lost to spoilage and infestations on its journey to the consumer. In developing countries, where tropical weather and poorly developed infrastructure contribute to the problem, losses are sometimes of staggering proportions. Losses occur in all operations from harvesting through handling, storage, processing and marketing. They vary according to the influence of factors such as the perishability of the commodity; ambient temperature and relative humidity which determine the natural course of decay; fungal and bacterial decay; damage by pests -insects, rodents and birds; the length of time between harvesting and consumption; and practices of postharvest handling, storage and processing.

Most often, postharvest losses are a symptom rather than the problem. Knowledge of their cause is, therefore, essential for deciding measures to prevent them. Such measures may have to be taken by the small farmer, the private trader, a cooperative, the marketing board or other operator, handlers and transporters, wholesale and retail markets, etc.

For FAO the focus of assistance is on the small farmers-men and women-who produce much of the food in developing countries and who often keep most of what they produce on the farm. Early FAO assistance concentrated on improving storage on small farms. However, losses at this level were often found to be negligible: most small farmers are both careful and imaginative in safeguarding the fruit of their labour within their existing possibilities. Thus over time FAO has shifted attention to the total postharvest chain, using loss assessment as a tool for understanding when, where and why losses occur. FAO's special action programme on prevention of food losses is now helping member governments to design and implement strategies for both prevention and reduction.

For rural storage and handling of farm inputs and outputs, FAO seeks to develop and make available farm and village level technologies that use locally available construction materials and involve building designs that reflect social and cultural traditions. In general, FAO's efforts in scientific research and development in agricultural engineering fosters optimum utilization of available human, financial and physical resources. In most developing countries this means encouragement to carry out applied rather than basic research with emphasis on direct farmer participation.

Development of the postharvest sector commonly requires inputs such as pesticides, cement, galvanized sheeting, wire netting, adequate packaging for the safe handling and transportation of perishables, sprays, boxes, and simple machines. Practical technical interventions are researched and promoted to prevent losses. For example, storage bins for grain must be cleaned out completely between seasons and disinfected before re-use; shade must be provided for holding perishables together with appropriate containers for their transportation and marketing. Improved technologies for drying fruits, vegetables and root crops have also been introduced to reduce losses arising from seasonal gluts.

Another critical factor for reducing food losses is quality standards and incentives for delivery of better quality produce through the introduction of a fair and practical grading system. The operation of such a system often calls for training and extension to improve handling, storage, packing, sorting and grading practices.

On a larger scale, FAO's projects include institution-building components and provide training in practical postharvest techniques. In Latin America, for instance, projects have helped train plant operators and other technical personnel in grain drying, aeration, fumigation, quality control and assessment, maintenance of machinery and installations, and in loss assessment. Manpower development also covers training in customs inspection, plant protection and quarantine.

Proper evaluation of postharvest technologies includes technical, economic and social components. It involves beneficiary participation throughout. Decisions to adopt new or improved technologies are made by individual farmers but their decisions are often strongly influenced by incentives and credit schemes, access to reliable sources of inputs, extension advice, training opportunities, and market information all of which are generally the responsibility of national governments or their agents.

Processing the output of agriculture

The role of agro-industries in economic development is often underestimated. These industries aim to improve the quality and increase the value of primary agricultural products. The resulting larger and more stable markets serve as a catalyst for further development of agriculture. In most developing countries, less than 20 percent of the agricultural output undergoes industrial processing compared with 80 or more percent in developed countries.

In many developing countries agro-industries are relatively labour intensive. They already account for about 25 percent of all industrial employment and offer scope for more, particularly for women. They are also important because of the diversity of technologies used, the wide range in scale of operation, the great potential for growth with equitable participation, and the enhancement of food security and nutrition.

Appropriate technologies for processing food in rural areas of developing countries are particularly needed. Traditional food technologies can sometimes be upgraded to enhance shelf life and consumer acceptance of indigenous foods as well as to develop value-added products with export potential. FAO has issued a compendium of traditional food processing technologies in Africa. It supports research for and establishment of small and medium-scale food processing industries. Emphasis has been placed on food preservation in rural and peri-urban areas, on small-scale labour-intensive/low-capital input installations, on use of locally available materials, and on import substitution.

Processing units for fruits and vegetables for both local and export markets have been developed, for example, at village and community level in numerous countries. With proper harvesting, postharvest treatment, grading, sorting and presentation, many fruits and vegetables have proved profitable for small-scale growers. Where introduction of controlled atmosphere techniques was feasible, more local and export markets could be reached than in the past. Special efforts have been made to promote apiculture through improvements in beekeeping technologies, hives and other equipment, and management methods. Enhanced control of processing has increased the yield and improved the quality of honey and beeswax.

FAO has promoted research on the processing of cereals, legumes and roots and tubers into flours that serve as indigenous convenience foods. In Africa, women's groups have been helped to improve the handling, storage and processing of cassava, maize and other staples, contributing to food security at the village level. In other regions, rice milling has been made more efficient through rehabilitation of existing mills and the setting up of new processing units. Rice parboiling has been introduced as a means of extending yield and improving nutritional value.

Another noteworthy achievement is the creation of a regional network on oil palm industry research and development in Latin America and assistance to the African Oil Palm Development Association, leading to better processing and increased production of palm oil in both regions.

Processing of meat and milk in developing countries is given great importance by FAO. It supports efforts to facilitate access to urban markets through better quality and longer shelf life of meat and dairy products brought about by improvements in the technology used by the small-scale rural processor.

New or modified technologies for slaughtering, meat handling and meat processing have been introduced for use in areas with an undeveloped infrastructure. Among these are small-scale abattoirs for hygienic slaughtering, means and methods for slaughtering in the absence of electricity and an adequate water supply, and mobile slaughter facilities.

Because refrigeration is rarely available in the rural areas of developing countries, FAO focuses on traditional and modern low-cost meat preservation methods such as meat drying and other technologies yielding low or intermediate moisture products. Research on processing methods aims to develop nutritious yet cheap products containing low-cost ingredients (e.g. offal, fat and non-meat ingredients) that can be afforded also by the poor in both village and city.

In milk collection and processing, FAO promotes the application of proven technology that yields products of adequate quality, uniformity and shelf life. A low-cost village-level processing model is being developed. This caters for collection zones with a radius of 5 km or less and collection of up to 500 litres of milk per day. The model's flexibility permits adaptation to different geographical and climatic conditions and to milk products for particular markets. Studies are in progress on the village-level use of microbial starters and on methods for obtaining rennet substitutes for cheesemaking.

FAO, with the support of Denmark, has mounted substantial and effective training programmes in milk and dairy development. These are implemented by three dairy development teams sited in Kenya, Chile and Thailand that serve their respective regions. A meat training centre for meat technology has been set up in Botswana for sub-Saharan Africa.

Agricultural products other than food should also be processed to increase value, secure markets and raise returns for primary producers. FAO has assisted in the development of processing techniques for natural fibres at farm and village levels. These techniques include scouring, grading, testing and processing of wool, mohair, alpaca, cashmere, cotton and jute. Labour-intensive small-scale or cottage industries, such as spinning, dyeing and weaving, require relatively low capital investment and have benefited rural women in particular. On a larger scale, introduction of a better system of cotton grading and marketing has been shown to increase incomes for the producers and has led to improvements at all stages from plant breeding to textile manufacture.

FAO has given special support to sericulture development through training in technology for the production and processing of natural silk. Improvements are promoted in mulberry tree cultivation and harvesting, silkworm breeding, cocoon production and disease control, silkworm egg production and silk reeling. This technology can bring high returns to small farmers, including women.

Utilization of non-food animal products is another basis for small-scale industrial development. Improved techniques are now available for flaying, curing and preserving hides and skins, and for using blood, bones, horns, hooves and intestines to produce marketable commodities such as glue, sausage casings, animal feed and fertilizer. FAO has also facilitated the introduction of the wet salting technique for curing hides and skins. This has improved the quality of the skins from goats and cattle, in many instances increasing their value by as much as 150 and 200 percent respectively.

A change in attitudes towards agro-industries is emerging, with greater awareness in governments of their importance to development. FAO encourages agro-industry as an integral part of agricultural sector planning in developing countries and assists in the formulation of the relevant plans, policies and programmes.

Food quality and safety

The safety of food is essential for the health and well-being of man, and its quality for his satisfaction. If quality and safety are to be assured, good practices must be used in the growing and postharvest handling of crops, the processing, packaging and distribution of the foods derived from them, and in their storage and preparation prior to consumption.

From the moment an edible raw material is harvested, gathered, caught or slaughtered, it undergoes progressive deterioration. The process may be very slow, as with seed or nuts, or so rapid as with milk or fish that the food becomes virtually useless in a matter of hours. Bacteria, yeasts, moulds, insects and rodents are in constant competition with man for his food supply. Foods are also subject to destruction by nearly every variable in the natural environment. Heat and cold, light, oxygen, moisture, dryness and natural enzymes within the food, all tend to cause deterioration

Efforts to preserve food aim to minimize the factors that lead to deterioration by processes such as drying, salting, pickling, sugaring, smoking, fermentation, even in refrigeration, packaging and frozen storage. A recently developed preservation technique is food irradiation which appears to hold considerable promise for some purposes in both developing and developed countries.

Most food-borne diseases are microbial in origin, but a bewildering array of biological and chemical contaminants can make food either inedible, dangerous to eat or lethal. Mycotoxins produced by fungi cause illness and numerous deaths every year, and leads to the loss of substantial amounts of food. The ever-increasing complexity of modern industrial society and the wide-ranging nature of the international food trade have increased the risk of the contamination of foods by chemical and biological agents. The contaminants may arise from environmental or industrial pollution (e.g. mercury, lead, arsenic), from agricultural technology (e.g. pesticide or veterinary drug residues) and from food processing practices (e.g. nitrosamines, polynuclear hydrocarbons). If any portion of the food chain should become contaminated, the contaminant is likely to enter the human food supply, presenting a potential hazard to human health as well as an impediment to food trade.

Scientific advances and better knowledge through research have supported older and newer technologies alike in their ability to ensure the safety and quality of the processed food supply. Unfortunately, the tools created for this purpose are not always available or applied, especially in less highly industrialized countries. Microbial contamination of food is long known to have been a serious problem in developing countries, whereas contamination by chemical residues including traces of heavy metals and radioactive elements has been documented more recently.

FAO participates with WHO in several programmes and activities designed to strengthen the ability of governments (and also food handlers and processors, and the consumer) to ensure the safety and quality of marketed foods.

The Joint FAO/WHO Food Contamination Monitoring Programme, a part of UNEP's Global Environment Monitoring System, has been in operation since 1976. Data are collected on the levels of important contaminants including pesticide residues, toxic metals and aflatoxins in selected foods and in total diet samples. These data can provide an estimate of the dietary intake of the contaminants and can be considered in establishing limits for them in foods. Some 40 collaborating laboratories across the world contribute data which are evaluated and published periodically.

A Joint FAO/WHO Expert Committee on Food Additives and Contaminants (JECFA) makes use of data from contamination monitoring along with results of toxicological studies in recommending maximum tolerable weekly levels of intake of contaminants by people. A Joint FAO/WHO Meeting on Pesticide Residues deals with these substances in the same way. The recommendations of the expert committees are subsequently used by Codex Committees of the FAO/WHO Codex Alimentarius Commission to define maximum residue limits in specific foods in ways that make it unlikely that the recommended maximum tolerable intake level is exceeded.

In handling and processing, substances may be added to food deliberately or adventitiously. JECFA has carried on the safety evaluation of such food additives (for example colours, flavours, enzymes, antioxidants and other preservatives, texturizers and processing aids) in about 40 meetings since 1956, recommending acceptable limits of daily intake by people for those additives for which a toxicological safety margin can either be established or is shown to be unnecessary because of the proven harmlessness of the substance. In recent years JECFA has also dealt with residues of antibiotics and other veterinary drugs in foods from animals.

Food quality is also determined by nutritional value. Another group of scientists, the Joint FAO/WHO Expert Committee on Nutrition, keeps this aspect under review and recommends minimum requirements of energy, protein, minerals, vitamins and other essential substances that should be supplied through food to the human body.

The Joint FAO/WHO Food Standards programme, established in 1962, operates through the Codex Alimentarius Commission, an intergovernmental body with over 140 members. The Commission, with its secretariat at FAO in Rome, makes practical use of the data and recommendations obtained from monitoring and expert evaluations. Through the internationally negotiated and adopted food standards that it issues, known collectively as the Codex Alimentarius, the Commission fulfills its primary mission: to protect the health of consumers and to ensure fair practices in the food trade.

The Codex Alimentarius Commission also promotes the assurance of quality and safety of foods through the publication of codes of good hygienic and technological practice. These codes embody the widest scientific knowledge with, however, an eye to the possibilities that exist in many developing countries. In the food trade, a main aim of the Codex Alimentarius is the reduction of non-tariff barriers. In the absence of agreed standards such barriers would be erected through special regulations on food labeling, food additives, residues of pesticides or veterinary drugs or traces of other contaminants in food, and food composition specifications.

These activities promoting food quality and safety at the international level must have their counterparts in every country. Governments have a lead responsibility with respect to food quality and safety in that they determine the fiscal, legal and technical environment in which the food producers and industry operate. Well-equipped laboratories, a competent inspectorate service, operating in the context of a sound body of law and regulations, and rigorous methods of sampling and analysis of foods are essential to an effective food control service. It must have analysts who are well-trained in the sciences, especially chemistry and microbiology, and inspectors who are fully conversant with the principles of food science and technology, hygiene and sanitation. FAO has assisted developing countries in all parts of the world with the establishment or strengthening of their food control services infrastructure or operations, with particular emphasis on training of inspectors and analysts, and by issuing manuals of food quality control.

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