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Effect of post‐cooking storage on texture and in vitro starch digestion of Japonica rice

Tamura, Masatsugu, Singh, Jaspreet, Kaur, Lovedeep, Ogawa, Yukiharu
Journal of food process engineering 2019 v.42 no.2 pp. e12985
Oryza sativa, digestibility, firmness, food industry, glucose, glycemic index, hydrolysis, in vitro digestion, microstructure, rice, rice starch, starch, storage temperature, storage time, texture
The effects of post‐cooking storage conditions on texture, microstructure and kinetics of glucose release during simulated in vitro digestion of japonica rice (Oryza sativa L.) were investigated. Cooked rice was stored at low, medium and extreme temperatures (4, 30 and 90 °C) for two different durations (1 and 24 h). The surface firmness of cooked rice grains stored at 30 and 90 °C was significantly decreased with an increase in the storage duration, while an opposite trend was observed for samples stored at 4 °C. Rice grains appeared shrunken and distorted during in vitro digestion, regardless of the post‐cooking storage conditions. The cooked rice stored at 4 and 90 °C, for 24 h showed significantly lower starch hydrolysis (%) than those stored for 1 h at similar temperatures. Pearson's product‐moment correlation coefficient indicated a significant negative correlation (p < 0.05) between the overall grain firmness and equilibrium hydrolysis (%) of stored cooked rice. PRACTICAL APPLICATIONS: Post‐cooking storage was found to be related not only to rice texture but also to rice starch digestibility. The reported results indicated that estimated glycemic index (eGI) value of cooked rice varied according to the post‐cooking storage conditions, which may help food processors in the development of low GI rice products. As overall rice grain firmness was found to be related to eGI, it can be employed as a parameter to evaluate the eGI of cooked rice.