Cold Storage of Onions

Onion is considered to be one of the world most important vegetable crops. In Sudan onion is commercially cultivated and stored by farmers using traditional ways such as storage in cottages made of straw or mud. Previous research by Shambat Food Research Center concentrated on this type of storage. In this research, experiments were conducted to investigate the effect of cold storing, at 0 oC temperature and 65% relative humidity, on two common varieties (Red Saggai, and Yellow Camelen). The two varieties are characterized by their high dry matter content and ability to store for a long period in traditional storage. Weight losses, sprouting losses, rooting losses, and rot losses were mrasured and compared with those from traditional storage. Heat loads for the stored onions were calculated and a suitable refrigeration unit was used and mounted on a container at Wafra for Modern Storage Company. The stored onions were packed in plastic sacks and loaded inside the cold store in six columns of different heights. Three samples each weighing 10 kg from each variety were randomly specified and their weekly losses measurements were taken. Experiment started in June 2000 and ended in Nov. 2000. Cold storage and ambient air temperatures and relative humidity during storage period were taken daily at 8:00 am and 2:00 pm. Weight losses, sprouting losses, rooting losses and rot losses were measured weekly. At the end of the experiment the overall losses for the stored sacks were measured. 5 Samples from the two varieties were stored in a traditional storage facility at Wad Ramly area north of Khartoum State and the losses were taken at the end of the storage period. At the end of the storage period it was observed that weight losses, sprouting losses and rot losses for cold storage were small compared with traditional storage. Also it was found that the effect of onion variety and sample location inside the cold store on the weight losses, sprouting losses rooting losses, and rot losses were statistically non- significant at 5% level. Losses were evaluated ecnomicaly at the end of storage period