The effects of cooking on extractable tannin, phytate, sugars and mineral solubility in some improved Nigerian legume seeds

The effect of heat treatment on nutritional and antinutritional parameters in some improved Nigerian legume seeds is reported. The tannin (0.9-3.9 mg/g catechin equivalent) and phytate (0.5-3.0 mg/g) contents were reduced by 11-84% and 13-32% respectively on cooking. Tannin content of Kersting's groundnut was reduced by 120%. Total sugar content was 8.7-16.7% in the raw samples but was also reduced by 8-30% on cooking. Stachyose was the predominant oligosaccharide. Cooking reduced the sucrose content by 50-60% and the oligosaccharides by 36-59%. Total and available iron contents were 51-117 mg/kg and 7.2-16.2% respectively, total and ionizable zinc content was low while total calcium and magnesium contents were high with adequate solubility during simulated digestion. Cooking improved iron availability and the ionization of zinc, calcium and magnesium by 19-100%, 22-104%, 18-83% and 11-61% respectively. There were significantly negative correlations between phytate tannin and mineral availability.