Preparation Of Defatted Soy Flour With High Dispersibility By Immobilized Protease

Defatted soybean meal is a byproduct of soybean oil with high protein content. Theuse of enzymatic modification to improve the dispersibility of the soybean meal, increasesits value and range of applications. The immobilized enzyme technology improves theutilization of the enzyme, which is widely used in the food industry. This paperimmobilized protease and optimized the hydrolysis conditions of the soybean defatted soyflour to improve the dispersion, which could be used to prepare highly dispersed soy flour.By determination of PDI, DH and bitterness of the enzymatic hydrolysates of defattedsoy flour, Alcalase2.4L alkaline proteases was suitable for enzymatic hydrolysis, thehydrolysate of which PDI was highest, DH was moderate and bitter was weak. Theoptimum conditions for enzymatic modified defatted soybean meal as follows: enzymeconcentration was50U/g soybean powder,pH9.0, temperature50℃, hydrolysis time was60min and substrate concentration was5%. Got in this condition, PDI and DH ofenzymatic hydrolysates of defatted soy flour were82.11±4.78%and21.67±2.54%.The enzyme activity recovery of immobilized protease preparing by cross-linkingembedding, embedding cross-linking and cross-linking method was studied in this paper.The results showed that: enzyme activity recovery of immobilized protease by cross-linkingwas up to47.75%,1.22and1.29times as the cross-linking embedding and embeddingcross-linking. The optimum conditions of preparation of cross-linking immobilized enzyme:the concentration of sodium alginate2.5%, enzyme dosage of2880U/g wet carrier,calcium chloride concentration3%, glutaraldehyde concentration1.2%, cross-linking time2h, and4h for immobilization. Compared with free enzyme, the immobilized protease byCross-linking, cross-linking embedding and embedding cross-linking, the optimumtemperature were increased by5,10and10℃, the optimum pH shifted to acidic1,2and2unit, the kinetic constants was1.65,2.18and2.34times that of the free enzyme, and thethermal stability and storage stability were significantly enhanced.The optimum conditions for defatted soybean meal enzymatic modified Alcalase2.4Lprotease immobilized by cross-linking as follows: enzyme dosage0.8g immobilizedenzyme/g soybean powder, pH8.0, temperature60℃, hydrolysis time90min andsubstrate concentration5%. Enzymatic modification experiments in this condition ofdefatted soy flour to get the hydrolysates, PDI and DH were75.36±5.85%and18.92±2.33%, the bitterness of the free enzyme and immobilized enzyme hydrolysates difference. Operational stability of the immobilized enzyme prepared by cross-linking wassignificantly increased, the catalytic activity of immobilized protease could retain66.2%after6times of enzymatic modification defatted soy flour.