Influence of ultrasound-assisted alkali treatment on the structural properties and functionalities of rice protein

The poor solubility of rice protein (RP) limits its applications in food industry. In this study, the effects of ultrasound-assisted alkali (UAA) treatment on the solubility, structure and functional properties of RP were investigated. Using UAA treatment, the solubility of RP increased with increasing alkali concentration, reaching a maximum value of 19.79 mg/mL at an alkali concentration of 0.08 M. The solubility was improved by 230-fold compared to un-treated samples. In addition, a reduction in particle size and degradation of the protein subunit were observed. UAA seemed to unfold the protein internal structural conformation and expose buried functional groups, which are linked to good emulsifying properties and foaming properties. A decrease in zeta potential was also observed after UAA treatment, which could be the reason for the decreased stability of the emulsion. UAA treatment modified the protein structure and significantly improved solubility.