Research On The Optimization Of Production Techniques Of Soybean Polypeptides And Its Bio-activity

The soybean protein has many good characters, such as high nutritional value, suitable amino acid constitution and good equilibrium of the essential amino acid. In China the soybean resources are abundant and the price is low. Therefore, there are broad applicable prospects in exploitation of soybean and its follow produces.The soybean protein hydrolysate, also called "peptide based protein hydrolysate "or "soybean polypeptides", has good characters and bio-activity. Compared with soybean protein, soybean polypeptides could improve material protein characters. For example, it has not special smell of soybean, no denaturation, not deposit in acid environment, no concentrate when heated, and it is more soluble etc. Moreover, the soybean polypeptides is absorbed directly by intestines. Soybean polypeptides has the resistant to oxidation, lowered blood pressure and cholesterin and so on .All of characters mentioned above are propitious for the development of soybean polypeptides in food, medicine and cosmetic field.Now, the research of soybean polypeptides is booming. While producing in factory just begin. The main point was lack of directing plan for manufacture. Otherwise, the bitter substances in hydrolysate would affect the taste of final products. And the technique of separation was not good.In this thesis, by second-order regression rotation designing, the mathematics matrix was established between the degree of hydrolysis (DH) by Protamex protease and five factor. The highly-produce scheme and the optimization design were also determined, which provided bases for manufacture and management. The optimization condition: hydrolysis time 10h., substrate concentration at 14%, the ratio of enzyme and substrate at 4.5%, pH6.5 and 40C.SPI (soybean peptide isolate) was hydrolyzed by double enzymes in order to reduce polypeptides' bitter-tasting in this experimentation. The Flavourzyme protease was appliedto Protamex protease hydrolysate. The results shows that the Flavourzyme protease optimal condition is at pH7.0, T50C, hydrolysis time 5h., enzyme concentration 2% of SPI. In this condition, the nitrogen contents is 0.178%, The bitter taste is lower than Protamex hydrolysate by 35.7%. Double enzymes method could achieve higher DH and lower bitter-tasting. According to the analysis, soybean polypeptides has many characters, such as good nutrition value, low viscidity, good moisture absorption and strong anti-oxidation ability etc..By tangential flow ultrafiltration (UF) technique, the scheme of separated soybean polypeptides and concentrated polypeptides could be achieved. By UF, the ratio of desalt is at 98.1%, the reclaim ratio of nitrogen is at 94.4% and the molecular weight cutoff at 3000 Dalton.At last, 3 kinds of polypeptides products were produced. The research is hoped to become the basis of theoretical part and the scheme of application.