The impact of cooking on the proximate composition and anti-nutritional factors of water yam (Dioscorea alata )

Raw and boiled water yam tubers (Dioscorea alata) were analyzed for proximate contents such as ash, crude protein, carbohydrate, crude fibre, crude lipid, energy and anti-nutrients using standard procedures and methods. The crude protein contents (10.27%), ash (2.93%) and lipid (0.15%) were significantly (p<0.05) lowered in the boiled tubers while the carbohydrate (76.57%) significantly (p<0.05) increased in the boiled tubers. The antinutrients; alkaloids (2.77%), saponins (2.71%), flavonoids (1.38%) and tannins (0.21%) significantly (p<0.05) reduced in the boiled tubers. It was concluded that boiling had both positive and negative effect on water yam. A cooking time of between 30 and 60 min at 100°C was recommended for D. alata.