Sha Yuki, Adachi Shuji
1 Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University.
J Appl Glycosci (1999). 2016 May 20;63(2):47-50. doi: 10.5458/jag.jag.JAG-2016_001. eCollection 2016.
The apparent density and porosity of four rice cultivars, Koshihikari, Yumepirika, Habutaemochi, and Kitayukimochi, decreased and increased, respectively, with the increasing temperature in the range of 5 °C to 60 °C. Especially large changes in both apparent density and porosity were observed at 60 °C, which can be ascribed to the starch gelatinization of rice. The swelling pressures of wet rice grains were estimated to be 7.5, 6.3, 6.2, and 5.9 MPa at 25 °C for Koshihikari, Yumepirika, Habutaemochi, and Kitayukimochi, respectively, from the distribution coefficients of solutes with different molar volumes. Rice grains having higher amylose content exhibited a weak tendency toward higher swelling pressure. The distribution coefficients of fructose for the Koshihikari and Habutaemochi cultivars were larger at higher temperatures, but the temperature dependence of the swelling pressure was not significant for both cultivars. These results suggested that the increase in the distribution coefficient was caused by the gradual relaxation of the interior structure of rice with increasing temperature.
在5℃至60℃范围内，越光、梦光、羽二重和北之雪这四个水稻品种的表观密度分别降低，孔隙率分别增加。在60℃时，表观密度和孔隙率都出现了特别大的变化，这可归因于水稻淀粉的糊化。根据不同摩尔体积溶质的分配系数，在25℃时，越光、梦光、羽二重和北之雪湿米粒的膨胀压力估计分别为7.5、6.3、6.2和5.9兆帕。直链淀粉含量较高的米粒呈现出膨胀压力较高的微弱趋势。越光和羽二重品种的果糖分配系数在较高温度下较大，但两个品种的膨胀压力对温度的依赖性均不显著。这些结果表明，分配系数的增加是由于水稻内部结构随温度升高逐渐松弛所致。
