Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA.
J Food Sci. 2013 Jul;78(7):H1076-81. doi: 10.1111/1750-3841.12165. Epub 2013 Jun 14.
This study aimed to understand effects of different cooking methods, including steamed, pilaf, and traditional stir-fried, on starch hydrolysis rates of rice. Rice grains of 3 varieties, japonica, indica, and waxy, were used for the study. Rice starch was isolated from the grain and characterized. Amylose contents of starches from japonica, indica, and waxy rice were 13.5%, 18.0%, and 0.9%, respectively. The onset gelatinization temperature of indica starch (71.6 °C) was higher than that of the japonica and waxy starch (56.0 and 56.8 °C, respectively). The difference was attributed to longer amylopectin branch chains of the indica starch. Starch hydrolysis rates and resistant starch (RS) contents of the rice varieties differed after they were cooked using different methods. Stir-fried rice displayed the least starch hydrolysis rate followed by pilaf rice and steamed rice for each rice variety. RS contents of freshly steamed japonica, indica, and waxy rice were 0.7%, 6.6%, and 1.3%, respectively; those of rice pilaf were 12.1%, 13.2%, and 3.4%, respectively; and the stir-fried rice displayed the largest RS contents of 15.8%, 16.6%, and 12.1%, respectively. Mechanisms of the large RS contents of the stir-fried rice were studied. With the least starch hydrolysis rate and the largest RS content, stir-fried rice would be a desirable way of preparing rice for food to reduce postprandial blood glucose and insulin responses and to improve colon health of humans.
本研究旨在了解不同烹饪方法（包括蒸、炒饭和传统炒）对米饭淀粉水解率的影响。研究使用了 3 种品种的大米，即粳稻、籼稻和糯稻。从谷物中分离出大米淀粉并进行了表征。粳稻、籼稻和糯稻淀粉的直链淀粉含量分别为 13.5%、18.0%和 0.9%。籼稻淀粉的起始糊化温度（71.6°C）高于粳稻和糯稻淀粉（分别为 56.0°C 和 56.8°C）。这归因于籼稻淀粉更长的支链淀粉侧链。不同烹饪方法对米饭品种的淀粉水解率和抗性淀粉（RS）含量有不同的影响。炒饭的淀粉水解率最低，其次是炒饭和蒸饭。新鲜蒸制的粳稻、籼稻和糯稻的 RS 含量分别为 0.7%、6.6%和 1.3%；米饭炒饭的 RS 含量分别为 12.1%、13.2%和 3.4%；而炒制米饭的 RS 含量最大，分别为 15.8%、16.6%和 12.1%。研究了炒制米饭 RS 含量大的机制。炒饭的淀粉水解率最低，RS 含量最大，是一种理想的烹饪米饭的方法，可以降低餐后血糖和胰岛素反应，改善人类的结肠健康。
