Optimization Of Enzymoiysis Process Of Soybean Protein And Study On Antioxidant Capacity Of Soybean Peptides

The soybean resource of china is more than that of any other country, and its source isquite rich. Soybean and their products are rich in quality protein, and soybean is a kind ofhigh quality protein crop in the food crops because of its protein being only close to theprotein of the full price. The soybean protein isolation is an important component of thesoybean, and its composition, structure and basic nature are similar to the pure soy protein.The soy protein has high nutritional value, is rich in quality protein and can provide the eightessential amino acids needed by the body, a variety of vitamins, minerals and so on. However,due to the complex molecular structure and larger molecular weight of soy protein (themolecular weight of80%of soy protein is above100000Da), there are lots of questions, suchas low solubility and digestibility, and biological titer is much lower than milk protein, eggprotein, and other animal protein and other problems. So in recent years, decomposing the soyprotein to improve the nutritional value and processing features of soy protein has become ahot topic.The methods of hydrolysis of soy protein isolation are mainly using acid, alkali andenzymes. However using acid and alkali to hydrolyze soy protein isolation has graduallybeing phased out, because the method is easy to make most amino acids racematization andno biological value, and react strongly to make the equipment serious corrosion. With therapid development of enzyme preparations and food industry, it was found that the use ofenzymatic modification not only had mild reaction conditions and light color products, andwas safe and reliable, and the enzymatic products were better in terms of nutrition, flavor andcrafts than that of using acid and alkali. Thus more attention was focused on the enzymatichydrolysis to obtain soy peptide. Soy peptide product has higher absorbency of digestion, andits amino acid composition is almost same to the soy protein, has balanced essential aminoacids, is with high nutritional value, but also has many physiological activity, such as low antigenicity, cholesterol-lowering effect, blood pressure lowering effect and antioxidantactivity, and so on, and is widely used in the fermentation industry, food industry and dailychemical industry.In this paper, the hydrolysis of soy protein isolation carried out mainly by proteases, andthe response surface method was used to optimize the hydrolysis conditions of a singleenzyme and complex enzyme hydrolyzing soy protein isolation, as well as the proportion ofcomplex enzyme and the optimum conditions of the oxidation resistance. The physical andchemical properties of soy peptide products were also reasearched. The results showed thatthe optimum conditions of the single enzyme hydrolyzing soy protein isolation were12%ofthe substrate concentration, hydrolysis temperature of46℃, and hydrolysis time of32h. Inthis condition, the content of amino nitrogen was0.77%; the optimum conditions of thecomplex enzyme hydrolyzing soy protein isolation were pH8.79, temperature50.46℃and10%of substrate concentration. In this condition, the DH was up to28.7%. The optimal ratioof the complex enzyme was alcalase39.6%,25.4%of the flavourzyme and neutral protease35.0%, and the optimum amount of [E]/[S] was3%(w/w); the optimal conditions foroxidation resistance were pH8.07, temperature56.08℃and12%of the substrateconcentration. In these conditions the reducing power was higher. Physical and chemicalproperties of soy peptide products were analyzed, and the studies had shown that soy peptideshad good solubility, emulsifying properties and oxidation resistance and so on, and theantioxidant activity gradually increased with the increase of DH of soy protein isolation, andreached a stable value. The results of soybean peptides in vivo digesting simulation showedthat soybean peptides were a good antioxidant. The pilot test of the production process of soypeptides was also researched in this paper. The results showed that the yield of soy peptideswere82.4%, and the purity greater than95%. For molecular weight, the amount of thepeptides less than1kD was2.63%, the peptides of1~5kD was58.07%, and the peptides ofgreater than5kD was39.3%, which was in line with national standards.