Effects of Roasting Temperature on Anti-Nutritional Factors and Antioxidant Property of Adzuki Bean (Vigna angularis) Flour

Abstract

Roasting process could be used to reduce the anti-nutritional factors (ANFs) of adzuki bean (Vigna angularis). In this research, adzuki beans were roasted for 20 min at different temperatures of 150 oC (R150), 165 oC (R165) and 180 oC (R180). The effects of roasting temperature on ANFs and antioxidant activity of resultant adzuki bean flour were investigated. Results indicate that roasting resulted in significant decreases in antinutrients including tannins (30 – 37%), and antitrypsin inhibitors (63 – 70%). Additionally, the reduction in trypsin inhibitors was proportional to the increase in roasting temperature. However, this trend was not observed in the reduction of tannins. Roasting also caused the loss of about 10 – 20% anthocyanin content, and hence the resultant antioxidant capacity of roasted samples also decreased as compared to that of raw bean flour. The results also imply that with low levels of ANFs and relatively high anthocyanin content, roasted adzuki bean flour could be potentially used in combination with or as substitutes for cereal flour in the preparation of bakery products.