EFFECT OF BAKING ON THE KINETICS OF ANTHOCYANIN DEGRADATION AND QUALITY OF PURPLE YAM (Dioscorea alata) PIES

Abstract

Purple yam (Dioscorea alata) contains a high amount of the natural pigment anthocyanin, which has antioxidant properties and helps in preventing diabetes and colon cancer. In addition, purple yam contains mucilage, which acts as a prebiotic and has a high moisture retention capacity. Purple yam is used in the production of baked goods with nutritional and sensory value. The objective of this study is to evaluate the effect of baking temperature (150, 160, 170°C) and baking time (20, 25, 30 minutes) on the quality of purple yam pie (moisture content, water activity, hardness, cohesiveness, anthocyanin content, L, a*, b*, H^o values, and sensory properties). Besides the 27 samples analyzed for physicochemical properties and anthocyanin content, the control (unbaked) sample was evaluated for anthocyanin to assess the kinetic reaction using the first-order and Arrhenius models. The results show that baking at 170°C for 20 minutes obtained the highest sensory scores, with a beautiful purple color and delicious flavor. The cake had a crispy crust and a tender crumb with with a moisture content of approximately 26 - 27% and the highest anthocyanin content of 7.52 mg/100 g. The first-order reaction model could be used to predict the remaining anthocyanin content in the purple yam pie when baked at different temperatures and times. The Arrhenius model was used to calculate the activation energy for the anthocyanin degradation process during baking, with the activation energy value of 49.48 kJ/mol. Anthocyanin content showed a strong inverse relationship with baking temperature, but a strong direct relationship with the cake’s moisture content. The research results not only provide scientific data on the changes in anthocyanin during baking but also highlight the potential for developing baked products from purple yam, contributing to the diversification of antioxidant - rich food products in the market.