Effect of cooking on the nutritional and phytochemical components of trifoliate yam (Dioscorea dumetorum)

Ezeocha V.C¹*, Ojimelukwe, P.C.² and Onwuka G.I.²

¹National Root Crops Research Institute, Umudike P.M.B 7006 Umuahia, Abia State

²Food Science and Technology Department, Michael Okpara University of Agriculture, Umudike, PMB 7267, Umuahia, Abia State, Nigeria.

*Corresponding Authors E-mail: avezeocha@yahoo.com

Accepted 21 August, 2012

Abstract

Trifoliate yam (Dioscorea dumetorum pax) obtained from the yam programme of National Root Crops Research Institute; Umudike was assessed to determine if cooking duration had any effect on their nutritional and phytochemical components. The tubers were cooked for 30mins, 60mins and 90mins, the nutritional and anti-nutritional compositions were evaluated while the Gas chromatography/ mass spectrophotometer (GC/MS) was used to identify the phytochemical components. Significant differences were observed in the proximate composition of the raw and the cooked tubers. Cooking for 90 minutes caused 29.81% loss in the crude protein of D. dumetorum. Cooking also affected the ash and fibre contents but the lipid content was not significantly affected. Cooking significantly reduced the alkaloid, saponin and flavonoid composition in Dioscorea dumetorum. The number of phytochemical compounds identified in the tubers cooked for 90 minutes were higher than those identified in the raw tubers. The Compounds identified in the tubers include fatty acids, phenols, hydrocarbons, esters, alcohols, aldehydes and ketones. The results obtained from the study showed that there were obvious quantitative and qualitative differences in the nutritional composition and phytochemical profile of raw and cooked tubers.

Keywords: Dioscorea dumetorum, Cooking, Fatty acids, anti-nutritional composition, Proximate composition.