Correlation between Taste of Cooked Rice and Properties of Gelatinization and Retrogradation

Abstract

The relationship between taste properties of cooked rice and gelatinization and retrogradation properties of rice was studied. Eight varieties of rice, differing in taste or amylose content, were examined for thermal properties as starch by Differential Scanning Calorimetry (DSC), pasting and gel properties as flour by Rapid Visco Analyser (RVA), and degree of gelatinization upon freeze-thaw stability and textural properties as cooked rice. Chukanbohonno 14 was the highest in gelatinization temperature and enthalpy by DSC, followed by Koshihikari and Nipponbare. On the other hand, Tomohikari and Hoshiyutaka were low in gelatinization temperature and endothermic energy according to DSC. Koshihikari showed high in peak viscosity, low in cooled at 50°C viscosity, and low in gel firmness, whereas Tomohikari as well as high-amylose rice was high in cooled at 50°C viscosity and gel firmness. Textural analysis of cooked rice indicated that good tasting rice was soft and high in adhesiveness as cooked rice. Firmness of Chukanbohonno 14 was between that of Koshihikari and Himenomochi, and its adhesiveness was higher than that of Tomohikari. Hence, tasting grade was related to gelatinization and retrogradation properties, and good tasting rice was high in gelatinization temperature and endothermic energy as measured by DSC, and high in viscosity and low in gel firmness. Upon cooking, good tasting rice was high in degree of gelatinization, low in retrogradation by freeze-thaw treatment, and high in increase of degree of gelatinization upon reheating.