Effects of ultrasound combined with hydrothermal treatment on the quality of brown rice

In order to improve the rough mouthfeel of brown rice, the effects of ultrasound (U) combined with hydrothermal (H) treatment on texture, sensory score and cooking quality of brown rice were studied, and the improvement mechanism was revealed from the aspects of room temperature water absorption, water droplet contact angle, microstructure and starch ordered structures. The results showed that ultrasound hydrothermal treatment cycle (UH-UH) can significantly improve the eating quality of brown rice. After UH-UH, the hardness, chewiness, optimal cooking time and volume expansion rate all reached to the level of white rice, and the stickiness significantly increased from 0.126 N of the control to 1.062 N. The sensory score of cooked brown rice rose from 57.37 to 76.70. On the other hand, room temperature water absorption rate far exceeded that of white rice, and the water droplet contact angle and relative crystallinity decreased significantly. In addition, scanning electron microscopy found that the cracks and micropores on the surface of treated brown rice grains increased greatly, which may be the underlying reasons for the improvement in the eating quality of brown rice. This study helps to provide a new way for producing high-quality brown rice.