Antioxidative Characteristics and Sensory Acceptability of Bread Substituted with Purple Yam (Dioscorea alata L.)

Abstract

In this study, plain bread was made by substituting wheat flour with purple yam flour (Dioscorea alata, L). The addition of 0, 10, 15, 20, and 30% purple yam flour aims to increase the functional value of plain bread as a source of natural antioxidants. The bread produced with two baking temperatures (170°C and 180°C) was tested for anthocyanin levels, total phenol, antioxidant activity (DPPH free radical scavenging), volume expansion, color, and preference test. The results showed that the temperatures of the bread baking did not affect anthocyanin levels, total phenol, antioxidant activity, volume expansion, and bread color ( $p>0.05$ ). The substitution of purple yam flour had a significant effect on anthocyanin levels, total phenol, antioxidant activity, volume, and bread color ( $p<0.05$ ). The levels of anthocyanins, total phenol, antioxidant activity, and darker color increased with the addition of purple yam flower whereas the rate of expansion reduced. However, the addition of purple yam flour did not affect the level of preference for the bread produced. Purple yam flour can be added to the manufacture of bread made from wheat flour as much as 30% with a baking temperature of 180°C. The resulting bread contained total anthocyanins 54.62 mg/100 g db, total phenol 391.14 mg EAG/100 g db, antioxidant activity 48.53% and volume expansion 64.85%, color $L^{\ast }=53.06$ , $a^{\ast }=6.52$ , $b^{\ast }=13.32$ , $C=14.87$ , $H=64.06$ , and $\text{sensory}\text{score}=3.24$ (preferred).