Abstract:In order to investigate the effects of high-temperature and high-pressure steam on the properties of rice bran, different high-temperature (121 ℃) and high-pressure steaming treatment durations were investigated. Lipase activity, physical properties (viscosity, chromaticity and microstructure), nutritional composition (soluble protein content, crude fat content and composition) and phytochemical composition (contents and activities of phytic acid, γ-oryzanol, phenolics) were determined. The results showed that the loss rate of lipase activity reached 81.86% after 1 min of steaming, and longer treatment did not significantly increase the lipase activity loss rate. The viscosity of the rice bran decreased from 14.67 cP to 7.00 cP, and the color deepened as the treatment time increased. Meanwhile, the micro-structure of rice bran became denser after treatment. The soluble protein content of rice bran decreased by 71.89%, while the extraction rate of crude fat increased by 5.94% after 1 min of steaming. The contents of phytic acid, γ-oryzanol and bound phenolics are not affected by steaming. However, the content of free phenols in rice bran reduces from 0.51% to 0.46%, and its ORAC (oxygen radical absorbance capacity) antioxidant activity decreases from 183.20 µmol TE/g DW to 149.22 µmol TE/g DW. The results revealed that 1 min high-temperature and high-pressure steaming at 121 ℃ is the optimal treatment for rice bran. These findings provide a theoretical guidance for the application of high-temperature and high-pressure steam in rice bran processing.
