Effects of storage conditions and storage period on nutritional and other qualities of stored yam (<i>Dioscorea</i> spp) tubers

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.

Keywords: Yam, storage conditions, nutritional, content

African Journal of Food, Agriculture, Nutrition and Development Vol. 9 (2) 2009: pp. 678-690