Preliminary Study On Preparation Of Antioxidant Peptides By Hydrolysis Of Okara Protein Using Aspergillus Niger And Composite Proteases

Soybean dregs is the main byproduct of soybean products processing, due to the residue of high moisture content, poor water solubility, taste rough and other reasons, have not been fully utilized over the years. This study by using fermentation combined with ultrasound-assisted alkali solution acid precipitation method to extract the protein of fermented soybean residue, Double enzyme with ultrasound-assisted hydrolysis soybean protein, determination antioxidant activities and ultrafiltrationi separation of soybean antioxidant peptide were studied, in order to provide part of the theoretical basis for the comprehensive utilization of okara. Results were as follows:With soybean dregs as raw material, using Aspergillus niger fermented bean dregs, then ultrasound-assisted alkali solution acid precipitation method to extract the protein of fermented soybean residue were applied. The results showed that fermentation can increase extraction rate obviously in the same extraction condition, ultrasound-assisted alkali solution acid precipitation method was better than single alkali solution acid precipitation to increase extraction rate and reduce the extraction time greatly; The optimal condition were as follows:ultrasound temperature was 55 ?, alkali extraction time was 90 min, NaOH was 0.3mol/L, ultrasonic power was 300 W, solid-liquid ratio was 1:24(g:mL), the best okara protein extraction rate was 83.84%.Soybean dregs protein was processed with ultrasonic (300 W,60 min), Then using flavor protease and papain to hydrolyze soybean residue to prepare soybean peptides.with the condition of double-enzyme, The optimal condition were as follows: flavor protease and papain ratio 3:1, enzyme concentration 6000 U/g, substrate concentration 6%, pH7.0, optimum temperature 50?, hydrolysis time of 6 h, the maximum DH was 36.92%.with the condition of optimal enzyme ratio, the optimum temperature, substrate concentration, pH, scavenging hydroxyl radical, reducing power, removing superoxide anion free radicals as an index To choose the optimal hydrolysis time, then separating soybean peptides by centrifugal ultrafiltration. The results shows that soybean peptide has strongest antioxidant effect when hydrolysis time is 5h,By ultrafiltration separation, molecular weight of soybean peptide under 2KDa has better solubility and strongest antioxidant effect.