Influence Of Ultrasound-assistant Alkali Treatment On Physico-chemical Properties Of Rice Residue Protein

Rice residue is the by-products of rice syrup industry.Its main constituents is protein which shows excellent balance of amino acid and hypoallergenic.Rice residue protein(RRP)have attracted attention from food industry.Because of the abundant gluten,it shows lower solubility.That also limit the application of RRP in food industry.The aim of is to investigate the effect of ultrasonic assisted alkali treatment on the properties of RRP.The main results were as follows:(1)The process parameters,including ultrasonic intensity,protein concentration and NaOH concentration,were optimized with single factor test firstly and then optimized by using response surface methodology.With the optimized treatment condition,ultrasonic intensity 19.2 W/cm,protein concentration 5.1%and NaOH concentration 0.08 mol/L,the RRP solubility was improved to be 19.79 mg/mL.Results of SDS-PAGE showed that the disulfide bond and subunit of RRP were destructed,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.(2)UAA treatment changed the protein structure and significantly improved solubility.In addition,a reduction in particle size and degradation of the protein subunit were observed.A decrease in zeta potential value was also observed,and RRP's peptides content is decreased and the proportion of hydrophobic amino acid is increased after modified by UAA.It seemed to unfold the protein's internal structural conformation and expose buried functional groups,both are linked to good emulsifying properties and foaming properties.(3)The spry dry processing of modified RRP is optimized by single factor experiment and response surface experimental design,the sequence of every factor for RRP's solubility was:inlet temperature>pH>outlet temperature.The optimal process conditions were as follows:pH 8,inlet temperature 180?;outlet temperature 86?.Under these conditions,the modified RRP's solubility reached 17.01 mg/mL.UAA assisted spry dry enabled protein to denaturalize which lead to the decrease in ?-sheet proportion,and the percentage of a-helix and ?-turns are both increased.RRP's hydrophobicity and particle size are reduced significantly.