Compositional and Functional Analyses of Dioscorea Odoratissima (Bush Yam) Flour and Starch as Influenced by Pre-Treatment

Dioscorea odoratissima (DO), an under-utilized famine crop is usually cooked, either peeled or unpeeled before consumption. Information on the effect of peeling on the nutritional attributes of D. odoratissima is scanty. In this study, nutritional and functional properties of flour and starch from peeled and unpeeled DO tuber were evaluated. Flour (UF) and starch (SU) from unpeeled yam tuber was significantly higher in starch compared to peeled yam flour (PF) and starch (PS), respectively. Crude protein content was significantly higher in UF and SU, compared to PF and PS. Alkaloids, phenolics, flavonoid, tannins, and trypsin inhibitor levels were significantly higher in UF and SU compared to PF and PS. PS exhibited significantly higher solubility, pasting clarity and swelling capacity compared to SU. In vitro starch digestibility, α-amylase and α-glucosidase activities positively correlate with amylose/amylopectin ratio in both flour and starch samples. UF and SU exhibited significantly higher antioxidant activity compared to PF and PS. These data emphasize the importance of pre-treatment with regard to applicability of DO flour and starch.