Effect of Incorporating Purple-Fleshed Sweet Potato in Biscuit on Antioxidant Content, Antioxidant Capacity and Colour Characteristics

Purple flesh sweet potato (PFSP) is considered to be a nutritionally rich crop. It also contain abundant amount of anthocyanin pigment which possess disease preventive properties. This work aims to study the effect of incorporating different form of processed PFSP, namely fresh, flour, and paste in biscuit formulation. Analysis was performed on the total phenolic, total anthocyanin content, antioxidant capacity, and colour characteristics. The analyses were made on samples, before and after the incorporation of PFSP in the biscuit. PFSP flour was prepared by directly using hot air-drying at 65 C for 18 hours while PFSP paste was steamed for 30 minutes at 100 C. The PFSP fresh contained total anthocyanin content at 21.40 mg CyE/100 g fw, and the content increased when processed into the form of flour and paste approximately at 38.90 mg CyE/100 g fw and 52.48 mg CyE/100 g fw, respectively. All forms of processed PFSP enhanced the purple colour when incorporated into the biscuit formulation. The experimental results showed that biscuit added with PFSP lost 15-36% of antioxidant capacity. Based on these findings, all forms of PFSP can be a natural colourant, a potential functional food ingredient, and can become a superior source for the production of foods with health benefits.