Optimizing the extraction of protein from broken rice using response surface methodology and comparing the protein functional properties

The application value of broken rice as a rich by-product in rice industry cannot be ignored. In this paper, Na2CO3 was used as extraction solvent and NaOH solution was used for control treatment to obtain broken rice protein (BRP) with high yield and good functional properties. Based on single-factor experiments, Response Surface methodology was used to determine the influence of the concentration of NaOH or Na2CO3, material-liquid ratio, and extraction time on the extraction rate of BRP. The maximum protein extraction yields were reached at 78.62% and 72.26% under the best extraction conditions of NaOH (0.08 mol/L, 1:13 g/mL and 3.0 h) and Na2CO3 (0.08 mol/L, 1:18 g/mL and 3.0 h). SDS-PAGE, FT-IR and DSC showed that changes in influencing factors during optimization process had different effects on BRP. There are significant differences in amino acid content of BRP, the content of essential amino acids in BRP obtained from the Na2CO3 group was higher. In addition, different extraction parameters had different influences on functional properties of BRP. This study provides new technical guidance for the development and utilization of rice by-product - broken rice to improve the protein extraction rate of broken rice in the industry.