The Denaturalization Of β-lactogobulin In Fresh Milk By Instantaneous High-pressure And Enzyme

Dairy industry is one of the most important mainstays in Chinese food industry. Instantaneous high-pressure processing technology,which has the technical features of low work pressure,continuous operation and easy to industrialization,has been developed to be a direction in the field of food ultrahigh pressure processing technology.To aim at industrialization of instantaneous high-pressure treatment,the effect of instantaneous high-pressure,enzyme and combined instantaneous high-pressure and enzyme on denaturalization of milkβ-lactoglobulin was researched.Single factors,including work pressure,feed temperature,processing time of instantaneous high-pressure,the amount of enzyme,hydrolysis time,pH and hydrolysis temperature(Pepsin,Trypsin,Neutral protease, Alkaline protease and Insulin),were investigated to reveal their effects on the degeneration ofβ-lactoglobulin(SDS-PAGE,hydrolysis degree and sulfhydryl content).On the basis of these results,a series of orthogonal experiments were performed to disclose the effect of combined instantaneous high-pressure and enzyme on denaturalization ofβ-lactogobulin.The experimental results were summarized and shown as follows:(1)Instantaneous high pressure,ranging from 20 to 60 MPa,led to cohesion ofβ-lactoglobulin.Cohesion ofβ-lactoglobulin improved accompanied with the stress increasing,but the too high pressure (80 MPa)caused depolymerization ofβ-lactoglobulin.The effect of temperature in range of 25 to 45℃was similar to that of instantaneous high pressure.But processing time(2 to 8 min)did not affectβ-lactoglobulin significantly.(2)Among the tested enzymes,the alkaline protease was most effective.The hydrolysis degree ofβ-lactoglobulin was up to 16.22%.The appropriate hydrolysis condition was summarized as follows:the amount of enzyme is 40 uL,hydrolysis time is 0.25 h,pH is 7.0 and hydrolysis temperature is 40℃). (3)Trypsin obtained the maximumβ-lactoglobulin sulfhydryl content.The optimum condition to obtain sulfhydryl content was shown as follows:amount of enzyme is 20 uL, hydrolysis time is 1.0 h,pH is 8.0 and hydrolysis temperature is 30℃.(4)Effect of all examined enzymes on both the hydrolysis degree and sulfhydryl content ofβ-lactoglobulin can be enhanced by instantaneous high-pressure pre-treatment.In all the cases,hydrolysis degree ofβ-lactoglobulin can be were up to the maximum under instantaneous high-pressure pre-treatment of 60 MPa.