Effect of Cooking Temperature on Mineral Content and Anti-nutritional Factors of Yam and Taro Grown in Southern Ethiopia

Abstract

Abstract This study aimed to determine the mineral composition and anti-nutritional factors, oxalate and phytate, of yam and taro grown in southern Ethiopia. In addition, the effect of cooking at different temperatures on the mineral compositions and anti-nutritional factors together with respective molar ratios Ca:oxalate, Zn:phytate, Ca:phytate and (Ca × phytate):Zn was determined. The mineral compositions were found to be: 21.8–15.7, Ca; 11.4–12.1, Na; 7.02–7.24, Mg; 6.47–14.14, Zn; 2.04–4.3, Fe; 0.26–0.88, Mn; 0.50–0.60, Cu; 0.57–0.82, Co; and 0.20–2.15, Ni in mg/100 g in the raw yam samples and 41–53, Ca; 6.21–7.21, Na; 7.32–7.58, Mg; 42–50, Zn; 1.93–3.25, Fe; 1.71–5.88, Mn; 0.46–0.51, Cu; 0.65–0.95, Co; and 0.18–0.68 Ni in mg/100 g of raw taro samples. Mineral content decreased by cooking except Fe and Ca in one variety of taro where they show a bit increment. The anti-nutritional factor to mineral ratio tends to imply that the relative bioavailability of the minerals after cooking was found to be increased except for that of Fe. These tubers may present health hazard potential, which in turn demands proper processing before consumption to eliminate the toxic effects of anti-nutritional factors.