A Preliminary study on the synthesis of phosphorylated sweet potato (Ipomoea batatas L.) starch

Abstract

Sweet potato (Ipomoea batatas L.) root is a traditional raw material for industrial starch production in central Asia (particularly China, Vietnam, Taiwan, and Korea). Sweet potato starch has superior free swelling and non-congealing characteristics, and therefore is a potential source of raw material for modified starch industry. In this research, a preliminary study has been performed to observe the effect of several process conditions on the physicochemical and functional properties of phosphorylated sweet potato starch. Phosphorylation of sweet potato starch was carried out at a temperature of 125 °C and initial pH level of reaction of 8-10 using a mixture of sodium tripolyphosphate and sodium trimetaphosphate (STPP and STMP, weight ratio of STPP/ STMP= 2.5:1) and an intake of 5%-weight STPP based on dry starch. The experimental result shows that phosphorous content of the products is accessible in the range of 0.154-0.180%-P. A significant improvement on solubility (6.56-14.10 %-w/w) and swelling power (9.36-12.82 g/g) has been achieved for the phosphorylated products compared to native starch (solubility = 2.33 %-w/w and swelling power = 7.36 g/g). Paste viscosity of the phosphorylated starch suspension (0.180 %-P, 1 g starch /100 ml) is higher (0.75 cP) compared to native starch (0.62 cP). Phosphorylated products also show improvement on paste clarity, and water absorption capacity. The result suggests that phosphorylation is a potential method to enhance the properties of sweet potato starch.