Effects of Storage Conditions and Storage Period on Nutritional and other Qualities of Stored Yam (Dioscorea Spp).

Abstract

Yam is one of the preferred staple foods in West Africa. The annual vegetative cycle of yam necessitates a long period of storage to make it available all year round. The major problems in yam tuber storage are sprouting, respiration and transpiration, which cause weight and quality losses. In this work, the effects of storage conditions and storage period on the nutritional and other qualities of stored yam tubers were investigated. Storage conditions used were two traditional yam barns, one with fan to aid air circulation and the other without. A total of 216 tubers of yam (Dioscorea roundata) “Giwa” variety with 108 tubers in each barn, were stored in the barns. Parameters evaluated were temperature and relative humidity of the storage environment, signs of deterioration of the tuber such as sprouting, weight loss and rotting and some nutritional parameters (carbohydrate, calcium, phosphorus, crude fibre, crude fat, crude protein, ash and moisture contents). Temperature and relative humidity were measured three times a week and four times a day at 0800h, 1200h, 1600h and 2000h. The results showed that average temperature and relative humidity in the barn with fan were slightly lower than that of the barn without fan. These differences were statistically significant for April, May and June at P< 0.1. Tubers stored in the barn with fan had the least sprout weight and least weight loss. At the end of a 3-month period, the tubers in the ventilated barn showed 4.7% less weight loss compared to the barn without fan. The difference in sprout weights and weight loss between the structures was statistically significant at P≤ 0.05. Also, tubers stored in the barn with fan had the least percentage of rotten tubers (1.85% of stored tubers) compared to the tubers stored in the barn without fan (12.03%). A reduction of some of the nutritional content was also observed during the six months of storage period. From these results it can be concluded that intermittent air flow on stored yam tubers reduces sprouting, weight loss and rot development, thus reducing the overall loss in stored yam tuber. However, moisture, crude protein, carbohydrates, phosphorus and calcium contents of the tuber reduced significantly in the two barns studied.