Abstract
The annual requirement of big onion in Sri Lanka is around 200,000 Metric tonnes and only about 25% is locally produced at present. Seasonal cultivation during April to September is mainly limited to dry zone areas of the country. About 30-50% postharvest losses are reported during short-term storage and sprouting and bulb rotting are the major causes of losses. Therefore, the objectives of this study were to study the present status of the onion postharvest handling, identify optimum storage conditions and analysis of the feasibility of providing those conditions for short-term storage. Primary and secondary data related to onion storage and marketing were gathered and analyzed to get information on postharvest handling, storage environment and marketing system. Storage behaviour of big onions under two temperatures: 25⁰C and 30⁰C and three RH conditions; 60%, 75% and 90% was studied using a locally fabricated environment control chamber. A complete randomized design was used for the experiment. Loss of weight and external quality parameters were studied. The rainy season coincided with the storage period developing high RH above 75%. Both the temperature and RH effects are significant at α =0.05 on the percentage losses but there is no interaction effect between these two factors. The difference in the weight reduction due to loss of moisture was significant under two temperatures and three RH conditions at α = 0.05. According to results 75% RH and 25⁰C temperature were found to be the best condition for storage. According to energy requirement estimation, the environmental control during storage is feasible. <strong>Key words: </strong>Bulb rotting; RH; Short-term storage; Temperature DOI: http://dx.doi.org/10.4038/tar.v22i4.3786 <em>TAR </em>2011; 22(4): 356-366
Highlights
Big onion is an important condiment in daily Sri Lankan diet with a constant demand throughout the year totaling to an annual requirement of around 200,000 tonnes (Customs report, 2009)
Problems encountered during handling the harvest in the fields, high relative humidity (RH) conditions, spread of diseases and unavailability of sufficient storage facilities further aggravates the losses
According to RH data records, the maximum RH occurs during early October to early January period (Fig. 4) and the day time RH values remain close to 90% which is a high value and the minimum RH during this period was always greater than 75%
Summary
Big onion is an important condiment in daily Sri Lankan diet with a constant demand throughout the year totaling to an annual requirement of around 200,000 tonnes (Customs report, 2009). Its main appeal is due to the characteristic flavour and pungency caused by the volatile oil allyl-propyl-disulphide. National production of big onion was 52,918 tonnes in the year 2008 Census and Statistics, 2009) which accounts for the 25% of national requirement. The production is limited to a seasonal cultivation from April to September and harvested during September and October. Off–season shortage leads to import of big onions
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