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Post-harvest food conservation

Post-harvest food conservation symposium - Rio de Janeiro
The role of post-harvest conservation of foods in achieving nutritional goals
Symposium on post-harvest technology and world hunger Kyoto, Japan
Utilization of post-harvest residues
Post-harvest losses: extent of the problem


Post-harvest food conservation symposium - Rio de Janeiro

A Symposium on Post-harvest Conservation of Foods was organized by Dr. Mogens Jul at the request of the organizing committee of the International Nutrition Congress in Rio de Janeiro, Brazil, as part of the Congress, held 27 August - 1 September 1978. The papers by Dr. Jul and Dr. Ramesh V. Bhat presented at that symposium are reported elsewhere in this issue. The other speakers were Dr. K. Saio, National Food Research Institute, Tokyo, and Dr. David Dendy, Tropical Products Institute, London.

Dr. Dendy called attention to the resolution adopted in September 1975 by the General Assembly of the United Nations stating: "The further reduction of post-harvest food losses in developing countries should be undertaken as a matter of priority, with a view to reaching at least a 50 per cent reduction by 1985."

Dr. Dendy discussed first the considerable losses occurring in the field during harvesting. Shattering of grain in the field at harvest time may often amount to 5 per cent of the harvest. Another common loss is that of grain left on the stalks, e.g., a 12 per cent loss for paddy threshed by beating. Where the stalk is burned this is a complete loss; where the stalk is fed to animals the loss is partly recovered in the form of meat and milk.

Losses also occur during storage, where they are mainly due to rodents, birds, and insects. These losses are probably the best studied and recent bibliographies issued by the Tropical Products Institute in London reflect this: the bibliography on storage had 265 references, whereas the one on all other aspects of post-harvest grain losses had only 206.

Losses may also be caused by improper drying or milling. Drying methods are generally capable of improvement, but improvements are difficult to implement at the village level. Losses in milling are often due to misuse of machinery, etc., which often leads to high breakage of kernels. This, however, may not result in total loss, but may produce rice of lower quality which is then sold at a lower price, a price that the poorer section of the population may be able to afford.

Parboiling rice leads to improved retention of vitamins but is not acceptable in large areas. Some lower yields in milling may be due to improper drying. Finally, considerable losses may occur in washing and cooking. Washing alone may cause a loss of rice solids of up to 2.6 per cent, while cooking may cause rice losses of up to 10 per cent if the cooking water is discarded.

Nutrition losses are of two different kinds that must be clearly distinguished. The first is avoidable and may be due to insects or micro-organisms. These can cause very consider able losses of vitamins and protein. Thus, heavily infested wheat showed a 1 per cent loss in weight after being stored for 11 weeks, but a yield loss of over 5 per cent of flour at 70 per cent extraction. Similarly, infested wheat may have a 38 per cent loss in food value after only 14 weeks in storage.

Another nutrition loss is that due to specific food habits. Many prefer to eat white bread and polished rice, although this kind of processing of wheat and rice results in losses of vitamin B. Similarly, toasting bread reduces its protein value considerably. Losses attributable to food habits are very difficult to avoid.

One loss may be due to anti-nutritional factors inherent in some foods. High-extraction flours may contain considerable amounts of physic acid that will immobilize part of the calcium, iron, and zinc in the diet. This is not considered a problem in industrialized countries where the diet is mixed and often enriched with these factors, but in less-privileged communities it may result in rickets and zinc dwarfism.

Dr. Dendy was somewhat skeptical about the prospects of reaching the target set by the UN General Assembly. Insofar as modernizing and improving storage and processing and avoiding quantitative losses, the cost of avoiding losses might be calculated. Nutrition losses would be much more difficult to measure and prevent. Thus, he mentioned that traditional washing of rice may result in 20 - 40 per cent losses of some of the B vitamins. A simple remedy would be to discourage the washing of rice.

The easiest method of achieving a saving in rice supplies would be at the milling stage, where a 5 per cent increase in output is frequently attainable with only modest further investment. Dr. Dendy concluded by stressing that measuring quantitative losses is often quite easy, and that they would be the obvious target to aim at in trying to lessen post-harvest losses.

Dr. Saio mentioned that soybean is becoming such an important food resource in Japan that the Ministry of Agriculture and Forestry now reserves a certain amount of the soybean harvest for emergency food stocks. Therefore, the National Food Research Institute has investigated the effect of aging on soybean quality. It was found that storage results in decreased product weight, lower yield after processing, and loss of nutrients.

Also important in soybean utilization is the fact that traditional soy processing was comparatively mild, while modern methods sometimes have been rather drastic, e.g., alkali or high-temperature treatments. These could result in the formation of lysinoalanine and lead to protein denaturation.


The role of post-harvest conservation of foods in achieving nutritional goals

Ramesh V. Bhat
National Institute of Nutrition, Food and Drug Toxicology Research Centre, Indian Council of Medical Research*

To increase the availability of food, the main emphasis during the last decade has been on improving yields of cereals and millets through breeding high-yielding varieties. It is now recognized that this alone may not be enough and that it is essential to conserve what is produced. In the field of post-harvest conservation of foods, the major thrust in the past 10 years has been directed toward determining quantitative food losses and assessing the means by which these foods are lost. As a result of these data, it should now be possible to initiate some concrete action programmes to minimize the qualitative and quantitative losses that occur at various stages of food handling, beginning on the farm and continuing during storage, at the market and in the household.

There have been several important developments both at the international and national levels over the past five years. The Seventh UN General Assembly in 1975 set a target of 50 per cent reduction in food losses to be achieved by 1985. If successful, this would mean a saving of 40 million tons of cereals and 5 million tons of pulses. In 1977 the FAO established a $US 20 million fund to combat postharvest food losses. In addition, a Group for Assistance on Systems Relating to Grain after Harvest (GASGA) has been formed. This group includes representatives of the Food and Agriculture Organization, Rome; the International Development Research Centre, Ottawa; the International Institute of Tropical Agriculture, Nigeria; the Food and Feed Grain Research Institute, Kansas, USA; and the Tropical Products Institute, London, England. The major programmes of this group include the correct assessment of post-harvest losses, adoption of methodologies to reduce them, the creation of awareness of such losses among people, and the training of manpower. The UN University in Tokyo has identified post-harvest technology as a priority item in its World Hunger Programme. All of these efforts should lead to a proper blend of applied research, training methodology, extension work, and appropriate intervention programmer.

It is perhaps appropriate here to mention the developments that have taken place in India in recent years that relate to post-harvest conservation of foods. An All-India Co-ordinated Project on Post-Harvest Technology was established in 1972 by the Indian Council of Agricultural Research (ICAR) to develop a technology for reducing post-harvest losses. The plan was initiated mainly at agricultural universities in order to develop appropriate technologies for handling, threshing, storing, milling, and conserving food, as well as for better utilization of the by-products.

A joint committee of the ICAR and the Indian Council of Medical Research ( ICMR) has been set up to co-ordinate research efforts to deal with problems of food contamination leading to outbreaks of disease in man. The Central Food Technological Research Institute, Mysore, has been continuing its research on applied aspects of minimizing food losses, especially through measures to protect grains against insect damage and through appropriate milling technologies for paddy, coarse grains, and pulses. These are in addition to training personnel at the international level.

A "Save Grain Campaign" has been launched by the Department of Food in the Ministry of Agriculture, and in this programme, practical training in scientific methods of storage and pest control is given to farmers, traders, and the personnel of co-operatives. Demonstration and publicity in selected areas to popularize correct methods of storage and pest control also form part of the activities.

A recent aspect of considerable importance has been a study to determine possible relationships between improper postharvest technology on the one hand and human disease on the other. Several episodes of food poisoning have been attributed, by the National Institute of Nutrition, Hyderabad, to such improper technology. Mycotoxins, weed seed contamination, and pesticide residues are three dangers which may be consequent on poor post-harvest practices. An outbreak of human aflatoxicosis resulting in the deaths of over 100 persons in parts of western India in 1974 - 75 was found to be due to the consumption of aflatoxin-contaminated corn that had been improperly stored. Ergot contamination of pearl millet, especially of the high-yielding varieties, is assuming serious proportions. Consumption of such grain by man leads to nausea, vomiting, dizziness, and prolonged somnolence.

Pesticides are often mixed directly with grain to kill insects. Consumption of such contaminated grains without proper washing has been known to lead to paralysis, as observed recently in parts of central India.

Several significant contributions have been made in different centres during the past five years under the post-harvest technology programme. The Paddy Processing Research Centre, Tiruvarur, India, has observed that spraying of a 10 per cent solution of sodium chloride on standing crops of ripening paddy can lower the moisture content in the grain from about 25 per cent to 16 per cent within 48 hours. Pest incidence in paddy treated by this means was reduced even after a year in storage.

Harvesting at the proper time also ensures better returns. The Central Rice Research Institute, Cuttack, has shown that head rice and milling recovery are greater if early and medium duration varieties are harvested between 27 and 33 days after 50 per cent flowering, and if late-maturing varieties are harvested between 33 and 39 days after 50 per cent flowering.

Sun-drying of agricultural produce is a common practice in tropical countries. According to the Rice Processing Engineering Centre, Karagpur, head-rice recovery by this method is about 80 per cent, while in mechanical drying it increases to nearly 90 per cent. The output of parboiled rice in a conventional mill is only 65 per cent compared with 68 per cent in modernized mills.

Parboiling of rice, which has been traditionally practiced in India, has several advantages, including increased nutritive value. Recent studies have indicated that the period of parboiling influences the extent of loss of various mineral nutrients during milling. Also, the bran of parboiled rice has more oil (20 - 25 per cent) than that of raw rice (15 - 20 per cent). In addition, deterioration of oil during storage is greater in raw rice bran oil because of its higher free fatty acid content.

Regarding storage structures, it has been shown that polythene-lined bamboo bins are more efficient than indigenous bins. The extent of insect infestation of IR-20 paddy variety in the improved polythene bin was 2.5 per cent compared to 4.5 per cent in unlined ones. Better storage can also be achieved by storing paddy in insecticide-impregnated gunny bags. Pest infestation was only 0.5 per cent in Phoxton-malathion-treated gunny bags, compared to 2.0 increased irrigation facilities were other causes. It is not easy to reverse this trend. However, by improving the milling technology and storage practices and minimizing insect attack, greater amounts of pulses could be conserved and made available to meet human protein requirements. Also, toxic legumes such as Lathyrus could be better utilized if subjected to detoxification.

Regarding milling technology, it has been shown by the Central Food Technological Research Institute that improved methods of milling will increase yields of chick-peas, green peas, pigeon peas, and black gram by 10 - 20 per cent. Coarse millets such as sorghum, pearl millet, and ragi (Eleusine coracana) are staples in India for the poorer segments of the population. The processing of these grains, e.g., pearling and removal of the outer husk, improves their appearance and consumer acceptability.

It is essential at this stage to attempt a cost-benefit analysis ratio. A study recently concluded by the Administrative Staff College of India at Hyderabad has indicated that the actual loss of food grains in India per year is 5.25 million tons. They also calculated the cost of grain loss per ton of grain in conventional and modern storage structures and found that this loss can be easily reduced by 50 per cent by using modern facilities. Storage requirements for the next ten years have also been calculated. The capacity to store 8.1 million tons of food grains will have to be developed by 1985 - 86. This would mean an additional investment of Rs 284 crores (Rs 2,840 million, or BUS 355 million).

However, cost should not be considered only in terms of profit. The accompanying social benefits to the community, such as generation of employment and improvement in community health that could ensue from improved food handling would not be insignificant. Economists have devised some simple formulae for calculating the cost-benefit ratio. For instance, the output value can be calculated by the following formula.

Net present value:

where B t = benefits at time t

C t = cost at time t
i= interest rate
t= time

In the next five years such a calculation should be made for the investments that have already been made and this should serve as an indicator for any future mid-course corrections.

The current need appears to be for conservation of food at several stages. Efforts at post-harvest conservation should begin at the pre-harvest stage by proper selection and breeding of the most suitable varieties of crops and by adjusting the time of sowing so that flowering and harvest time coincide with minimal rainfall. Proper natural drying facilities such as sunshine, mechanical and solar driers would help to recover more grain. Modern methods for milling pulses and cereals would minimize loss of both grains and their nutrients

Improving existing storage structures by appropriate rural technology using locally available, cheap resources, and minimizing losses from rodents, microbes, and insects would save considerable amounts of food grains. Utilization of by-products through agro-industries not only generates more employment, thereby increasing purchasing power, but also leads to better conservation. Recovery of rice bran oil is a good example.

Appropriate methods, such as solvent extraction for extraction of oilseeds, would yield at least 10 per cent more oil.

Although this poses the problem of solvent residues if food-grade solvents are not used, it would certainly increase the availability of this valuable commodity. Another sector that needs top priority is the conservation of perishables such as milk, vegetables, and fish.

To obtain the best results in the field of post-harvest technology, a systems approach that involves co-ordination among the various disciplines is essential. At the moment post-harvest conservation appears to be a no-man's-land, left mostly to the farmer, trader, and the consumer. Interaction with agronomists, plant breeders, mycologists, entomologists, cereal chemists, agricultural engineers, food s. technologists, oil technologists, economists, clinicians, pathologists, and epidemiologists would possibly strengthen the efforts.

Finally, we have had slogans to designate various concentrated efforts - "The Green Revolution," "Operation Flood," "Save Grain Campaign," etc. It would now be appropriate to have a campaign such as the "Grow More Food Campaign" that India had years ago, aimed at attaining self-sufficiency in food. This new effort could be aptly called the "Conserve More Food Campaign." Man has succeeded in producing more food; he should also succeed in conserving it.


Symposium on post-harvest technology and world hunger Kyoto, Japan

A Symposium on the Potential of Post-harvest Technology for Alleviating World Hunger was organized by Dr. Mogens Jul at the request of the United Nations University World Hunger Programme as part of the Fifth International Congress of Food Science and Technology, held in Kyoto, Japan, in September 1978.

The discussion was initiated by Dr. H. A. B. Parpia, FAO, Rome, who analyzed the nature and magnitude of the world hunger problem, whose solution requires not only increased production of food, but maintenance of its quality through use of appropriate technologies for post-harvest conservation and processing, including those for food manufacturing by-products. Raising income levels through alternative employment for rural populations was seen as fundamental to overcoming the hunger problem and transforming socio-economic conditions.

Participants who elaborated on specific aspects of the problem and its solution were: Dr. Bharat Bhushan, Deputy Director, Regional Research Laboratory, Hyderabad, India; Dr. Joseph Hulse, International Development Research Centre, Ottawa, Canada; Dr. F G. Winarno, Professor, Agricultural University, Bogor, Indonesia; Dr. Agide Gorgatti-Netto, Director General, Instituto Tecnologia Alimentos, Campinas, Brazil; Dr. John Nabney, Tropical Products Institute, London, England; Mrs. Charity Edwards, Federal Institute of Industrial Re" search, Lagos, Nigeria; and Dr. Patrick Ngoddy, Professor, University of Ife, Ile-Ife, Nigeria. The discussion was chaired by Dr. Mogens Jul. Royal Veterinary and Agricultural University, Copenhagen, Denmark. (Papers by Drs. Bhushan and Gorgatti-Netto follow )

The panel first discussed quantitative post-harvest losses. These were estimated at 10 to 20 per cent for cereals and 15 to 40 per cent for horticultural crops, with similar losses for other perishable products. The panel agreed that much effort was being exerted to assess more accurately the postharvest losses of cereals. The greatest need now would, therefore, probably be to assess losses of legumes and perishable foods.

Second in importance would be an assessment of qualitative losses, i.e., losses in nutritive value caused by damage during storage, transport, or processing.

The panel considered possible action to alleviate these losses and stressed that not all of them are easily avoided. Preventing food losses may, at times, require substantial additional resources, but will be increasingly justified by the

2 rapidly rising cost of inputs for raising production per hectare. The panel generally agreed that for cash crops, especially export crops, modern technologies such as those used in industrialized countries are often appropriate. One member referred to the successful storage of soybeans in aerated silos in Brazil, and to the effective use of controlled atmosphere or refrigerated storage for perishable products. More important, however, would be the development of village-level storage and processing methods. Several descriptions were given of successful underground storage of maize and other cereals. It was generally agreed that in this area, low-income countries could learn little from the industrialized world. It would be more appropriate to establish an exchange of information and technologies among developing countries and to utilize improved traditional technologies, on which a considerable amount of work has already been done, or is in progress.

Another aspect of post-harvest technology was stressed by several panel members. Agriculture is the main occupation for most people in developing countries, especially for the poorer classes. If the migration toward urban areas, where usually little employment can be found, is to be reversed, employment must be generated in the rural areas, and the obvious choice is development of agro-industries and agri-businesses. For reasons of investment, environmental considerations, and often insufficient supplies of raw material, it is generally best to consider the establishment of small, but economically viable, plants.

One calculation was that 40 tons of oilseeds could be processed per day either in one large plant or in ten minor plants that would rely on ten expellers, five splitting plants, and one fatty-acid distillation and glycerol-recovery plant. The first alternative would require an investment of about $US 1.5 million, while the other would require about $US 0.8 million. The number of persons employed would be 91 or 338, respectively, and the annual rate of return on investment would be 0.98 in the first case and 1.94 in the second. Thus, investing in several smaller plants rather than in one central processing unit would be more economical and would generate many more jobs.

A similar calculation was made for paper mills. One large paper mill using straw as raw material, with a 250-ton-per-day capacity, employing 3,000 persons, would require an investment of $US 100 million. A mini-plant producing 5 tons per day would require an investment of $US1 million and would employ 150 persons. Such mini-plants have been set up in India and have proved profitable and at the same time preferable from a socio-economic view.

The panel reviewed the cost of investment for each job generated in the food-processing industries. The figures approached $US 5,000 - 7,000 per job, except in the Republic of Korea, where the cost is less than $US 1,000.

It was emphasized that it is extremely important to train manpower for the organization and management of food science and technology institutions, and for leadership in research and training. This is vital to the building of capabilities in the developing countries for solving their own food and nutrition problems. It will also foster co-operation if a network of institutions is established in the developing countries for exchange of information among them.


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