Tentative Estimation of the Degree of Gelatinization of Abnormally Cooked Rice Using Amylographic Characteristics

Abstract

We determined the amylographic characteristics of various rice specimens to clarify the degree of gelatinization of hot water-treated rice (abnormally cooked rice obtained by prolonged steeping at 75°C for 8-18h). The maximum viscosity of the rice specimens tested decreased in the following order: warm water-treated rice (rice steeped at 60°C for 24h), raw rice, hot water-treated rice, aged rice (cooked rice stored at 5°C for 48 or 96h), cooked rice, pressure-cooked rice, and alkaline-gelatinized rice. There was an inverse relationship between the maximum viscosity and the degree of gelatinization. We proposed a tentative scale based on the maximum viscosity to estimate the degree of gelatinization. We adopted values for warm water-treated rice and alkalinegelatinized rice as gelatinization standards of 0% and 100%, respectively. Using the new scale, the degree of gelatinization for hot water-treated rice was estimated to be 30-47%, while that for cooked rice was 67-75%.