ABSTRACT
The feasibility for commercial application of radiation processing for enhancing food security by reducing post-harvest losses in agricultural products are discussed in this paper. It is reckoned that a sizeable quantity of world’s food production is lost due to damage caused by bacteria, mould, insects and other pests. The major cause of post-harvest loss encountered in stored grains and other dried food crops is feeding by larvae and adults of several stored products insects. Many of the post-harvest chemical fumigants currently in use for control of insect infestation, such as ethylene dibromide (EDB), methyl bromide (MB) and ethylene oxide (ETO) are either banned or to be phased out because of their adverse impact on human health and environment. There are also reports of development by major grain pests of higher levels of resistance to phosphine, the other major grain fumigant used worldwide. Therefore satisfactory long term storage of staple crops may be at risk as the traditional fumigants are phased out and/or due to development of increased insect resistance. Practical control of insect pests, regardless of species or stage of development is possible by low dose irradiation in the dose ange of 0.2 to 0.5 kGy. The advantages include short treatment time, no undesirable chemical residues in the food, no resistance developed by the insects and no significant changes in the physicochemical and functional properties or the nutritive value of the product.
Delaying the processes of ripening and over ripening in may fruits have been observed following treatment of the fruits in the physiologically mature but unripe state to low doses of ionizing radiation in the range of 0.25 to 1.0 kGy. More ofien, it is advantageous to combine irradiation with other post harvest procedures such as refrigeration, modified atmosphere and packaging to derive maximum benefits in terms of increased shelf-life. Combined treatments of radiation and hot water have been shown to provide good control of post harvest fungal rots and can be an effective alternative to chemical fungicides, some of which have been withdrawn in the recent times in view of their harmful effects on human health. In berry fruits such as strawberry, the mould free refrigerated shelf-life could be increased by irradiation at 2 kGy or by a combination of CO2 and irradiation below 1 kGy.
Sprouting in tuber, bulb and root crops during storage is inhibited by irradiation at doses in the range of 0.02 to 0.15 kGy. The inhibition of sprouting is more effective when these crops are irradiated soon after harvest and curing when the commodities are in the dormancy period. However, it is important to control losses on account of microbiological spoilage by appropriate storage management such as aeration, temperature and humidity control of the storage environment. Large commercial scale irradiation of potatoes has been carried out in Japan since 941974. Since mid 1990’s China has implemented large scale irradiation of garlic, up to 70,000 tons per annum in recent years, for sprout control. Pilot-scale studies in many countries have demonstrated the commercial feasibility of irradiation for sprout control on onions and yams under tropical storage conditions.
Radiation processing can thus provide an effective and safe alternative treatment for improving food security in many of the developing and less developed countries by reducing post-harvest losses of staple and non-staple crops when coupled with good handling, storage and transport practices.
