Process optimization of increase the solubility of rice residue protein by ultrasound-assisted alkali treatment

This study was to improve the solubility of rice residue protein ( RRP) with ultrasound-assisted alkali treatment ( UAA) .The process parameters, including reaction temperature, ultrasoinc time ultrasonic intensity, protein concentration and Na OH concentration, were optimized with single factor test firstly and then optimized using response surface methodology. The optimized treatment condition were reaction temperature 50 ℃, ultrasonic time 60 min, ultrasonic intensity 19.2 W/cm², protein concentration 5.1% and Na OH concentration 0.08 mol/L, the RRP solubility was improved to be ( 20.09 ± 0.58) mg/m L.Results of SDS-PAGE showed that the disulfide bond and subunit of RRP were subjected to destruct, the insoluble protein aggregates was dissolved by the UAA treatment.Determination of particle size showed that the protein size decreased significantly from 485 nm to 223 nm. All above attributed to the solubility improvement. These results indicated that UAA treatment was beneficial for promoting RRP processing techniques, it might be a promising manufacturing technique in food industry.