Title : Effects of soaking treatment on the microstructure, gelatinization properties, thermal characteristics and cooking quality of brown rice
Abstract:
Brown rice presents several technical challenges during cooking, such as slow water absorption, inadequate gelatinization, and an undesirable texture. Soaking pretreatment is commonly employed to address these issues. In order to evaluate the effect of soaking technology on the application quality of brown rice grains, brown rice was soaked at 30°C, 40°C, 50°C, and the quality of brown rice was evaluated at different soaking times (0, 1, 2, 3, 4, 5, 6, 7, 8 hours) by measuring its water absorption characteristics, microstructure, water distribution, gelatinization characteristics, and cooking characteristics.The results indicated that prolonged soaking time and elevated soaking temperatures facilitated the formation of surface wrinkles and cracks, as well as a honeycomb like structure in the cross-section. The pores between starch granules enlarged, leading to an overall more porous overall structure. Furthermore, the water absorption rate and gelatinization enthalpy of brown rice, free water content, iodine blue value and expansion rate of cooked brown rice increased significantly, whereas the gelatinization time and peak time of brown rice decreased. The water absorption rate, gelatinization enthalpy, and swelling ratio reached saturation after 4 h of soaking, beyond this duration, the changes in these parameters became less pronounced. Cooked brown rice soaked at 40 ℃ and 50 ℃ exhibited similar iodine blue values . and expansion ratios, which were both significantly higher than those soaked at 30 ℃. Soaking at 40 ℃ for 4 h was identified as a critical point for the evaluated indicators, Considering both the effectiveness and economic factors, soaking at 40 °C for 4 h was determined to be the optimal and most economical condition for improving the processing characteristics of brown rice.
