Content of anthocyanins was determined by following the procedures of Mancinelli, Huang Yang, Lindquist, Anderson, and Rabino (1975). The sweet potato flour (0.5 g) was treated with 20 ml of acidified methanol (1% HCl) in a rotary mixer at a 45° angle and 200 rpm for 30 min in the dark. After centrifuging at 450 g and 4 °C for 15 min, the supernatant was diluted to an appropriate concentration and the absorbance was read at 657 nm (A657) and 530 nm (A530). The anthocyanin content was calculated on the basis of the following equation: