Effect of heat treatments on proximate composition of sweet potato tubers

Abstract

Sweet potato is an important member of root and tuber crops which serve as a carbohydrate source for large populace in many developing countries. Its tuber is subjected to various heat treatment processes in its conversion from the raw form into final products which can be readily consumed. This study investigated the effects of heat treatment methods on the proximate composition of processed sweet potato tubers. White- and yellow fleshed sweet potato tubers used for this study were sourced locally from Bodija market in Ibadan metropolis, Oyo State, Nigeria. The tubers were subjected to three common heat treatment methods namely boiling, roasting and frying. Sweet potatoes from each of the heat treatments were subjected to proximate analysis. The results obtained shows that the heat treatment methods did not have any significant effect (p≤0.05) on the carbohydrate content of both varieties. Boiling, on the other hand, had significant effect (p<0.05) on the ash, fibre and fat contents while it had no significant effect (p<0.05) on the moisture and protein contents of both varieties. Roasting had no significant effect on the fat content although it had significant effect (p<0.05) on the ash, fibre, protein and moisture contents of both varieties. All the investigated heat treatment methods had significant effects (p<0.05) on the crude fibre and ash contents of both varieties. All the heat treatment methods effectively retained most of the nutrients in the sweet potato tubers within acceptable limits for human consumption. However, frying resulted in increased fat content which is often recommended to be avoided by the medical practitioners and dieticians to avoid the attendant health risks. Boiling is recommended when products of higher moisture and protein contents are desired.