Effect of extrusion processing on the microstructure and in vitro digestibility of broken rice

During rice dehulling and polishing, about 14% of the rice will be broken. How to utilize those low-value broken rice effectively is a critical issue. In this study, extrusion technology was applied to restructure the broken rice. The morphology, molecular structure and digestibility of intact, broken and extruded rice were investigated with SEM, XRD, FT-IR as well as simulated in vitro gastrointestinal digestion technique. The extruded rice showed a rough surface and the crystalline structure transformed its diffraction type from an A-type to a mixture of B- and V-types. The equilibrium starch hydrolysis (C∞) and kinetic constant (k) of extruded rice was significantly lower than that of the broken rice, which was 76.10%, 2.91 × 10−2 (min−1) and 80.90%, 6.42 × 10−2 (min−1), respectively. Our results indicated that extrusion processing could modify the microstructure and digestibility of rice effectively, and be an optional way to produce staple rice with lower digestibility.