Effect of Soaking Prior to Oven-Drying on Some Nutrient and Anti-Nutrient Properties of Bitter Yam (Dioscorea dumetorum)

Abstract

Soaking may improve the bitter yam properties processed by traditional method of drying and milling. The Dioscorea dumetorum study investigated the effect of soaking prior to the traditional method of drying and milling on some nutrient and anti-nutrient properties of bitter yam flour. Four equal parts of cleaned, peeled and sliced bitter yam tubers were respectively soaked in clean water for 6, 12, 18 and 24 hours, dewatered, oven-dried at 50°C and milled, using standard procedures. The peak effect was recorded in the sample soaked for 24 hours which increased respectively by 13.12%, 29.41% and 0.81% for moisture, fat and carbohydrate, but decreased by 19.61%, 11.44%, 10.85%, 48.00% and 47.17% for crude fibre, ash, protein, alkaloid and tannin relative to control. Soaking, irrespective of time, prior to oven-drying (50°C) significantly improved the moisture and fat contents, but diminished the studied anti- nutrient and the other nutrient content of the bitter yam flour. The processing method did not favor the preservation of most of the studied properties. We recommend soaking prior to oven drying when the desired effect is overriding. Further studies, including sensory evaluation are warranted to address the possibility that the method may yield less bitter flour.