A comparative study on retrogradation of rice starch gels by DSC, X-ray and alpha-amylase methods

摘要

The degree of retrogradation (DR) of 10 and 50% rice starch gels, which were stored at refrigerator, room temperature and freezer for 1, 3 and 6 days, were investigated by DSC, X-ray diffractometry and alpha-amylase-iodine methods. Besides being affected by moisture content and storage conditions applied, the nonwaxy rice starch gels were retrograded faster and higher than the waxy ones. DR of 50% starch gels was higher than that of 10% starch gels. In case of 50% starch gels, DR increased in the following order: refrigerated > room temperature > frozen. For 10% starch gels, no typical X-ray pattern of the retrograded starch was shown, while DSC and alpha-amylaseiodine method gave information on DR of starch gels. Due to interpretative sensitivity of the data obtained, alpha-amylase-iodine method was suggested as an adequate means for the DR of starch gels.