Rapeseed Peptide Preparation, Purification And Activity Of Anti-oxidation

Application of ultrasonic-microwave used to extract rapeseed protein was studied in this paper. Rapeseed protein was hydrolyzed into antioxidant rapeseed peptides by protex6L.The antioxidant rapeseed peptides were separated by poliglucan gelatin Sephadex G-15. Finally the antioxidant activities of rapeseed peptide and its different fractions were studied. The main conclusions of the experiments were as follows:(1) Preparation of rapeseed protein:With the extraction ratio of rapeseed protein as the index,based on the single factor and response surface experiments,the optimum conditions of protein extraction were studied.The results showed that microwave power, pH, extraction time and the ratio of solvent to meal were significantly affected extraction ratio. In addition, the interaction of microwave power and extraction time were significance,so were extraction time and the ratio of solvent to meal. According to response surface analysis, the optimum extraction conditions were rapeseed meal of60mesh, microwave power of80w, pH value of12,extracting time of500s, the ratio of solven to meal of20:1,extracted times of3, under which the protein extraction rate reached90.54%.Uitrasonic-microwave synergistic extraction was time saving and gave a higher extraction yield of rapeseed protein,the extraction rate increased7.74%when compared with the conventional water bath extraction method.(2) Preparation of rapeseed peptides by enzymatic hydrolysis:This project studied the enzymatic hydrolysis techniques. Five types of Proteases(Protex6L、Protex7L、Protamex、 Alcalase2.4L and Flavourzyme)were selected by antioxidant activity and hydrolysis degree (DH).The results showed that the optimal protease is Protex6L. The optimal hydrolytic conditions for rapeseed protein was enzyme dosage5430U/ml, pH10, temperature55℃, concentration of rapeseed protein [S]2%(w/v), time2h by single-factor and D-optimal tests. Under the optimal conditions, the value of antioxidant activity is33.64mmoltrolox/100g,and the degree of hydrolysate is15.88%.(3) Isolation and purification of rapeseed peptides:After the separation of rapeseed peptides with polyglucan gelatin Sephadex G-15,three peptides ingredients were gotten, which were R I RⅡ and RⅢ. The relative molecular mass of each component is365,300and120after HPLC analysis.(4) Antioxidant activity of rapeseed peptides:The antioxidant activities of rapeseed peptide were studied by measuring the ability of superoxide radicals, hydroxyl radicals, ABTS radicals, DPPH radicals and their reducing powers. The results showed rapeseed peptides had strong antioxidant activity,especially for scavenging hydroxyl radicals, and the ability of RIII was higher than Vc;The antioxidant activity of rapeseed peptides with molecular weight was inverse.The smaller is molecular weight,the stronger is its antioxidant activity. The relative molecular mass of RIII was minimum,but the antioxidant activity was strongest.