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Comparison of Starch Physicochemical Properties of Waxy Rice Cultivars with Different Hardening Rates

Sasaki, Tomoko, Kawamata, Kai, Okamoto, Kazuyuki
Cereal chemistry 2017 v.94 no.4 pp. 699-704
amylopectin, crystal structure, cultivars, digestibility, endothermy, enthalpy, glutinous rice, physicochemical properties, rice cakes, texture
The objective of this study was to investigate the starch characteristics of a novel waxy rice cultivar Hitachimochi 36 (H36) with an extremely slow hardening rate of waxy rice cake and the relationships between starch physicochemical properties and texture of waxy rice cake. Starch isolated from H36 showed significantly higher digestibility than that from other waxy rice cultivars, and the starch digestibility highly correlated with the starch crystallinity. The compressive force of the starch gel prepared from H36 was significantly lower than that from other cultivars when stored at 5°C for five days, which reflected the differences in endothermic enthalpies corresponding to retrograded amylopectin. Various textural parameters of cooked waxy rice cake prepared from H36 were also remarkably different from those of cooked waxy rice cake prepared from other waxy rice cultivars. The cooked waxy rice cake prepared from H36 exhibited the lowest compressive force and breaking force by tensile and rupture tests, respectively. The analysis of amylopectin chain length distribution indicated that amylopectin of H36 contained higher proportions of the short chains. The difference in amylopectin chain length distribution and lower crystallinity of starch contributed to the unique textural properties of waxy rice cake prepared from H36.