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Abstract Handling and storage processes are considered the most important factors affecting the quality of the agricultural products after harvesting. After preliminarily surveying for the most effective problems facing the handling and storage of the agricultural products, it was found that, under the currently used system for oman storage in Egypt, the bulk of onions is stored in the field where they are placed in piles covered with rice straw and kept under the ambient conditions for 5 months. During the Summer period, the average temperature is high (35°C) and the relative humidity is low (30%) while in the rainy season, rhe temperature is around 21°C and the relative humidity is more than 60 %. The dimensions of these piles vary from a farmer to another and from one place to another. The total weight losses of onions for this method are about 50 %, which are mostly due to moisture loss and deterioration by insects and microorganisms. Moreover, the losses due to harvesting and handling of onions before storage amount to 7.4 % of the total production (CAPMS of A.R.E.,1980-1994). In Egypt, the onion is one of the most important crops, not only for local consumption but also for export, and is considered one of the main sources of hard currency. The Egyptian onion is grown as winter crop in Middle and Upper Egypt in August to September and it is harvested in January to February. In Delta area, onion is grown as a summer crop in October to November and harvested in May to June. It is grown also as an interplanted crop for mature dry bulbs and green bunch in February to March, and harvested in July (Morsy et al., 1959~Eweida et al., 1986~El Kafoury, 1986~ and EI-Sheekh et al., 1994). In 1993, the total cultivated area was 63302 ha and the total production was 1150334 tonnes (18.17 ton.zha). Most Middle and Upper Egypt onion production is devoted for export and all production of Delta onion is used for domestic consumption (CAPMS of A.R.E., 1980- 1994). Although Egyptian exports represented 80.4 % of total African exports in 1993, exports of Egyptian onions have decreased from 159000 ton in 1965 to 137560 tonnes in 1993 (FAa, 1976-1993) due to the decreased production in the Middle and Upper Egypt and the increased local consumption. Also, the delay in production, the unsuitable packages used for exports, and the complicated operations in shipping are reasons for decreased exports (Saleh et al., 1992). For sound storage of onions, important factors such as cultivation practices, harvesting and curing time, control of temperature and humidity in the store, storage structure design, and application of sprout-inhibiting chemicals play major roles. Onions as perishables have an optimum temperature range for storage, above which, they respire at unacceptably high rates and are more susceptible to ethylene and disease damage. According to Robinson et al. (1981), Wang (1982) and Kader (1986), most horticultural commodities respire at rates which double, triple, or even quadruple for every 10°C (18 OF) increase in temperature. On the other hand, temperature below the optimum will result in freezing or chilling damage. The optimum conditions to store onions are O°C temperature and 65-70% relative humidity (RH) with adequate air circulation (Hardenburg et al., 1986~ and Smittle 1988). No commercial application has been identified for varieties with long storage potential for controlled atmospheres (CA). Onions are damaged by < 1% O2 and 10% C02. There is some commercial use ofCA (3% O2 and 5-7% CO2) for sweet onion varieties (short storage potential). Losses in quantity and quality occur in onion crops between harvest and consumption. The magnitude of postharvest losses of onions are estimated to be 5 to 25 %in developed countries and 20 to 50% in developing countries, depending upon the commodity (Kader, 1985). The main aim of this work was to evaluate the current Egyptian storage system for onions and to develop an appropriate system for onion storage that will minimize the losses, preserve the quality of onions and prolong the storage life of onions in order to overcome the supply demand problem during the rest of year and keep the onion prices stable through the whole year. |