Fatty acid composition of Dioscorea dumetorum (Pax) varieties
The purpose of the present investigation was to study the fatty acid compositions of edible and wild Dioscorea dumetorum (Pax) varieties harvested from farms and forests of Ikot Akpanabia village in Akwa Ibom State, Nigeria in order to evaluate their nutritional and biochemical significance. Tubers were conveyed from farm sites wrapped in clean dry paper in cardboard boxes to the laboratory. Samples were washed, peeled, sliced and oven dried for 6 hours at 55°C before analysis. Fatty acids were determined in both varieties of Dioscorea dumetorum using gas chromatographic technique. Total fat content was low in both varieties with the wild variety recording the lowest (0.45%) but were not significantly different (P>0.05). The percentage composition of individual fatty acid ranged from 0.12% to 35.08% for edible Dioscorea dumetorum and 0.11% to 39.77% for the wild variety. The most abundant fatty acids in the two varieties were palmitic (C 16:0, 22.9-29.8%), oleic (C 18:1, 14.5-17.7%), and linoleic (C 18:2, 35.08-39.77%), with the wild variety recording higher values except for palmitic acid. Generally the fatty acid compositions of the two varieties Dioscorea dumetorum were patterned in a similar way and only trace amounts were obtained for caprylic (C 8: 0), Capric (C 10: 0), hendecanoic (C 11: 0), arachidonic (C 20: 1) and erucic (C 22: 1) acids. The unsaturation ratio was higher in the wild Dioscorea dumetorum (1.60) than the edible Dioscorea dumetorum (1.20). There were differences in the fatty acid profiles of the edible and the wild Dioscorea dumetorum though not in all fatty acids. Dioscorea dumetorum varieties were found to also contain unusual fatty acids, erucic and hendecanoic acids. The two varieties were found to be good sources of the essential fatty acid (linoleic acid) with the wild D. dumetorum being a better source of fatty acids for the teaming Nigerian population if it is processed for consumption or commercial purposes.
Key words: Fatty acids, Dioscorea dumetorum, yam, varieties