Abstract:

In order to improve the hydrolysis of soy protein,soy protein was prepared through alkali extraction and acid precipitation,and pepsin was applied to treat the soy protein for two hours to hydrolyze the glycinin. Then,alcalase and protamex were used to carry out further hydrolysis,and the molecular mass distribution of the corresponding products was determined by means of SDS-PAGE and GPC. The results show that ( 1) as compared with the single enzyme treatment without pepsin,pepsin pretreatment greatly improves the protein recovery,the degree of hydrolysis and the ORAC ( Oxygen Radical Absorbance Capacity) value of the hydrolysates,and the corresponding maximums are up to 95. 4%,23. 1% and 1078. 6,which are 39. 9%,35. 9% and 38. 5% higher,respectively; and ( 2) the molecular masses of the hydrolysates with pepsin pretreatment are mostly under 10 ku and mainly range from 1 to 5 ku. The above-mentioned results indicate that pepsin pretreatment can promote the hydrolysis of soy protein and enhance the antioxidant activity of the hydrolysates.

Key words: soy protein, pepsin, protein recovery, degree of hydrolysis, antioxidant activity, molecular mass distribution