The Extraction And Enzymatic Hydrolysis Of Rapeseed Protein And Its Protein Hydrolysates’Antioxidant Activity

This paper study on the preparation of rapeseed protein using low temperature rapeseed meal as raw material.Based on the enzymic hydrolysis preparation of4types protease of rapeseed peptides studied,we choosed the two protease with superior antioxidant activity to combinatorial hydrolyze. The rapeseed peptides antioxidation conditions of double enzyme hydrolysis were optimized. Then the antioxidantion properties of rapeseed protein hydrolysates in vitro were studied.The extraction parameters were optimized with the extraction rates of protein as the index, through the experiment of single factor and response surface methodology including pH, extraction temperature, solid to water ratio, extraction times, extraction time. The optimal conditions were pH12, extraction temperature55℃, solid to water ratio1:18, extraction times3, extraction time30min.By acid treatment,alkali treatment and heat treatment (70,80,90,100℃),the preprocessing of rapeseed protein were studied and compared with untreated group. It showed that acid treatment, alkali treatment and different temperature treatment group had not significant increase degree of hydrolysis (DH), so we choosed untreated rapeseed protein as a follow-up tests material.The degree of hydrolysis(DH)and reducing power activity of rapeseed peptides obtained by4types of proteases were studied, and the results showed that the optimizing hydrolysis condition of alcalase are substrate concentration1%, pH9.0, hydrolysis temperature55℃.quantity of enzyme7000U/g,the highest DH was17.08%. The optimizing reducing power condition of alcalase were substrate concentration2%, pH9.0, hydrolysis temperature50℃.quantity of enzyme5000U/g,the highest reducing power was1.362.The optimizing DH condition of papain were substrate concentration1%, pH8.0, hydrolysis temperature60℃,quantity of enzyme12000U/g.the highest DH was14.81%. The optimizing reducing power condition of papain were substrate concentration1.5.%, pH8.0, hydrolysis temperature60℃.quantity of enzyme11000U/g.The highest reducing power was1.370.The optimizing DH condition of flavourzyme were substrate concentration1.5%, pH8.0, hydrolysis temperature40℃,quantity of enzyme5000U/g,the highest DH was11.89%. The optimizing reducing power condtiion of flavourzyme were substrate concentration2.%, pH8.0, hydrolysis temperature45℃,quantity of enzyme5000U/g.the highest reducing power was0.813. The optimizing DH condition of protamex were substrate concentration1.5%, pH8.0, hydrolysis temperature60℃,quantity of enzyme9000U/g,the highest DH is13.48%. The optimizing reducing power condition of protamex is substrate concentration1.25%, pH7.0, hydrolysis temperature50℃,quantity of enzyme10000U/g,the highest reducing power was1.105.The hydrolysis capacity order of4types of proteases was alcalase> papain> protamex> flavourzyme.The reducing power order was papain> alcalase> protamex> flavourzyme.In order to define the double enzyme hydrolysis conditions, the parameters of double enzyme hydrolysis of alcalase and papain were studied. The results showed that step enzyme hydrolysis was better than synchronous hydrolysis. During step enzyme hydrolysis, the antioxidation of rapeseed peptides when the first kind of protease deactivated was better than the first kind of protease inactivated. The order was adding alcalase first and then papain.The antioxidation of rapeseed protein hydrolysates were determined in vitro. In a certain concentration range (Omg/mL-20mg/mL),the enzymic hydrolysates of rapeseed protein had scavenging ability hydroxyl radical,the maximum scavenging rates to-OH free radical were88.69%.The maximum scavenging rates to O2-·free radical was50.0%,the maximum reducing power were1.929.The results showed different detection method of antioxidation of rapeseed peptides both have certain antioxidant effect.