Evaluation of the Effects of Boiling on the Nutrient and Phytonutrient Composition of (Aduh) Aerial Yam Tubers

This study investigates proximate, mineral and phytonutrient composition of raw and boiled yam (Aduh) flour samples. The aduh samples were divided into two equal portions. The tubers were sorted by removal of defected tubers and divided into two equal portions of one kilogram each for the pre-treatments One portion was processed raw and the second potion was subjected to boiling treatment. The proximate and mineral composition was analyzed using the method of AOAC, (2010) while the method described by Onwuka (2005) was employed in determining the phytonutrient content. The results of the proximate composition showed that the raw aduh sample had moisture content (6.37%), ash (2.33%), crude fibre (3.64%), crude protein content (9.81%), crude fat (3.86%), carbohydrate (77.21%) and energy value of 369.94%. The values of the raw sample were higher than that of the boiled sample due to the leaching away of nutrients into the boiling water. The mineral composition showed that the flours contained 205.60 – 316.31 µg/100g calcium, 139.00 – 161.00 µg/100g magnesium, 440 – 920.00 µg/100g potassium, 550.00 – 640.00 µg/100g sodium, 590.00 – 1735 µg/100g iron and 152.00 – 412.00 µg/100g zinc, respectively. The phytonutrient composition of the raw aduh flour were alkaloids (2.16%), flavonoids (1.75%), saponins (1.27%), tannin (0.21%) and phytate (1.88%) were significantly (p<0.05) reduced during boiling treatment process. Boiling treatment led to great reduction of the anti-nutritional factors. However, a slight reduction in the nutrient parameters was observed for the boiled sample but such reduction cannot be compared with the positive gains of removal of antinutrients. Thus, it is recommended that Aduh be properly cooked for at least 60 min before consumption.