Texture and Digestion Properties of Cooked Rice and Rice Noodles

Abstract Rice varieties high in amylose content have low glycemic and insulin responses. Rice noodles are processed by extrusion from high amylose content rice, which may also have low glycemic and insulin responses. In this study, cooked rice and rice noodles processed from two high amylose content cultivars, Guangluai4 (GL4) and Zhenguiai (ZGA), were chosen for in vitro starch digestion evaluation. Apparent amylose content of cultivars (i.e., GL4-28.4% and ZGA-26.8%) and pasting properties except final viscosity were significantly different between the cultivars. In vitro starch digestion results showed that the glucose production rate in rice noodles was significantly slower than that in cooked rice by 65.7% and 42.0% in GL4 and ZGA, respectively. The main reason for low glucose production in rice noodles was active digestion duration longer in rice noodles than in cooked rice, which reflects the slow release of glucose during starch digestion. The texture of rice noodles in the GL4 and ZGA cultivars is 3 and 2.3 times harder than that of cooked rice, respectively. Thus digestive enzymes can hardly enter the interior of rice noodles for amylolysis. As a result, the digestion time of rice noodles is longer, and the release of glucose during digestion is slower than that of cooked rice. The slower release of glucose during rice noodle digestion may be beneficial for prolonging satiety and reducing food intake. Consequently, eating rice noodles may help in improving or preventing diabetes and obesity over time.