Effects and Mechanism of Dilute Acid Soaking with Ultrasound Pretreatment on Rice Bran Protein Extraction

Abstract This research focused on enhancing protein extraction from defatted rice bran (DRB) by using ultrasound combined with dilute sulfuric acid-soaking pretreatment. The extraction yield of protein was increased from 53.1% to 72.8% when the DRB was pretreated by ultrasound combined with 0.9% sulfuric-acid soaking at 90 °C. Untreated and pretreated DRB were then characterized by scanning electron microscope (SEM), fourier transform infrared (FTIR), and thermogravimetry analysis (TGA). The physicochemical analysis showed that combined pretreatment could significantly cause changes of chemical structure and reduce the thermalstability indicating the destruction of matix structue of DRB. This destruction would improve the accessibility of solvent to protein resulting in increase of protein extraction yield. Overall, the consequences of this investigation demonstrate that combined pretreatment is a comparatively effective process to extract protein from DRB, and the obtained results also prove a valuable insight into mechanism of protein extraction.