Preparation Of Soybean Peptide And Its Application In Food

Soybean peptide is usually produced by acid hydrolysis, enzymolysis or microbial fermentation from soybean, soybean meal or soybean protein. In the food industry enzymolysis and microbial fermentation were the major means to produce soybean peptide. Soybean peptide has a promising prospect for food industry, it has physical properties such as easy to dissolve, easy to absorb, low-viscosity and functional properties such as antioxidant, lower the blood pressure, lower the cholesterol etc. There are some problems in the preparation of soybean peptide:the degree of hydrolysis and the peptide yield is low, the flavor is poor, the application range is narrow, It’s necessary to do further research on the preparation conditions and its application of soybean peptide.This research studied the preparation method of soybean peptides by compund enzymatic hydrolysis, increased the degree of hydrolysis and the peptide yield and the effection of soybean peptide on Lactobacillus fermentation, in addition, utilized the rest of protein after the extraction of soybean peptide, developed a method to product an acidic asoy protein solid beverage, which avoided the waste of soybean protein and reduced the cost.(1) The optimization of enzymatic hydrolysis coditions for the preparation of soybean peptideA enzyme and papain were chosed to hydrolysis soybean protein, and the short peptide recovery as the main index, the degree of hydrolysis as the secondary index.The process for producing soybean peptides:first, the soybean protein was pretreatmented; then soybean protein was hydrolyzed with enzyme; at last the index was tested.The optimization result of pretreatment condition indicated that the heatmeant of substrates before hydrolysis had no significant effect on the short peptide recovery. When the homogenization treatment pressure was 20Mpa, the degree of hydrolysis was 13.7% compared to the control (8.25%), it was significantly increased (P<0.01); the short peptide recovery was 75% compared to the control (64%), the difference was significant (P<0.01).The single factor experiment results showed that it’s suitable for industrialized production when the substrate concentration was 8%, the amount of A+papain was 2%, the proportion of A enzyme and papain was 2:1 (w/w), the pH value was 7, hydrolysis 90min at the teamperature was 50 ℃.An experiment was did at the optimal conditions of enzymatic hydrolysis,at last,the degree of hydrolysis was 15.3%,the crude soybean peptide recovery was 82.32% and the short peptide recovery was 73.21%, the crude soybean peptide (0.6mg/mL) scavenged 26.72% of the superoxide anion free radical. There was 87.5% of soybean peptide less than 1 OKDa in the final peptide production.(2) Enzymolysis method was used for debittering of soybean peptides with Flavourzyme and ProteaseAXG. The single factor such as time, temperature, the enzyme proportion, the enzyme dosage and pH were reserched, finally an orthogonal experiment was carried out. When analyzing the effect of single factors on the debittering, the result showed that the enzyme proportion>temperature>time>pH on the effect of debittering. The optimum conditions were obtained as follows:the proportion of ProteaseAXG and Flavourzyme was 2:1 (w/w), the total amount of mass was 0.2%, the pH was7, hydrolysis 80min at the teamperature was 50℃, the bitter value was 1 that could be accepted by consumers.(3) Lactobacillus bacteria growed faster in the experimental group that soybean peptide added than the control, the pH value and acidity curve also showed that soybean peptide could promote the accumulation of lactic acid and reduce the fermentation time. When 0.7-1.1% soybean peptide was added in the Yogurt raw material, the acidity increased significantly.(4) An acidic soy protein solid beverage ingredients was produced with the rest of protein after the extraction of soybean peptide. When analyzing the effect of single factors on the stability of the beverage, the results showed that drying method>mixing method>the ratio of soybean and soybean polysaccharide>pH value before drying. The optimal preparation conditions was obtained as follows:the ratio of soybean protein and soybean polysaccharide was 1:0.26, the pH value was 6 before drying, mixing soybean polysaccharides and maltodextrin, then soy protein was mixed, spray drying, and collect powder in collecting tub, the sedimentation rate was 0.95% and the sensory evaluation was 12 that was moderate.In this research, the optimum conditions of preparation of soybean peptide was gotten, debittering of soybean peptide worked well, the study found that soybean peptide was good for the lactic acid bacteria fermentation, an acidic soy protein solid beverage ingredients was successfuliy produced by the residue protein. The research results provided data support for industrial production and expanded the application of soybean peptide.