Measurement of Thermal Behavior and Amylose Content of Kuzu and Sweet Potato Starches

Abstract

The thermal behavior of kuzu and sweet potato starches was investigated by differential scanning calorimetry (DSC). In the present experiment, samples were defatted with 85% methanol solution. Heating speed of DSC was programed at 5deg/min. Peak area (cal/g) and three temperatures, i.e. onset, peak (T_p) and conclusion temperatures were measured. T_p of kuzu starch was lower than that of sweet potato starch and distributed in the range of 60 to 69.3°C. The starch produced in Korea was the lowest and that produced in Nara was the highest in them. In sweet potato starch, T_p was in the range of 72.5 to 74.3°C and no difference of the place of production was observed. Amylose content of kuzu and sweet potato starches was measured by the iodo-starch reaction. Defatted samples were gelatinized with 1 N sodium hydroxide solution, reacted with iodine, and then the absorbance of the complex was measured at 680nm. Amylose and amylopectin prepared from kuzu starch were used as standard. The amylose content of kuzu and sweet potato starches was in the range of 19.0 to 22.6% and 21.5 to 22.0%, respectively.