Enzymatic Hydrolysis Of Corn Gluten And Separation And Purification Of The Hydrolysates

Corn gluten meal, by-product of corn starch processing, contains more than60%protein.Zein and glutelin are the primary protein components, So far corn gluten meal is mainly usedas animal feed and fertilizer. Physicochemical properties and bioactivities of corn glutenhydrolysates, glutelin hydrolysates and zein hydrolysates have been researched, but researchabout the systematic comparison of antioxidant activities among those hydrolysates has beenreported rarely. In this thesis, corn gluten meal was used as materials to extrect glutelin andzein. The enzymatic hydrolysis conditions of three proteins were optimized by responesurface methodology. The antioxidant activities of the hydrolysates were investigated, and therelationship between molecular mass of the hydrolysates and antioxidant activities wasanalyzed.Three proteases (Alcalase, Neutral protease and Papain) were choosed to hydrolyze corngluten meal, the result showed that hydrolysates prepared by Alcalase have the bestantioxidant activity. Then the enzymatic hydrolysis conditions of corn gluten, glutelin andzein hydrolyzed by Alcalase were optimized by single factor experiment and response surfacemethodology. The optimum enzymatic hydrolysis conditions of corn gluten were: enzymeamount3.13%, pH8.6, hydrolysis time4.3h, hydrolysis temperature56℃, substrateconcentration1%, and under these conditions, the reducing power of corn gluten hydrolysateswas0.617; The optimum conditions of glutelin were:3.35%,8.3,4.15h,56℃,1%,respectively, and under these conditions, the reducing power was0.673; The optimumconditions of zein were:2.33%,8.3,4.30h,58℃,1%, respectively, and under these conditions,the reducing power was0.496.Antioxidant activities of corn gluten hydrolysates, glutelin hydrolysates and zeinhydrolysates prepared under the optimum conditions were also discussed. The relationshipbetween the degrees of hydrolysis (DHs) and antioxidant activities, and the relationshipbetween concentrations of those hydrolysates and antioxidant activities were estimated. Theresults indicated that DH had no corresponding relation with antioxidant activities, butconcentrations of those hydrolysates had a dose-dependent relationship with antioxidantactivities. By comparing IC50, the DPPH and O2-scavenging activities of corn glutenhydrolysates were better than glutelin and zein hydrolysates, while DPPH and O2-radicalscavenging activities of the three hydrolysates were all lower than ascorbic acid. The OH scavenging activity of zein hydrolysates was better than corn gluten and glutelin hydrolysates,and OH scavenging activity of the three hydrolysates were better than ascorbic acid.In order to explore the relationship between antioxidant activities and molecular mass ofcorn gluten hydrolysates, sephedax G-25gel filtration chromatography was used tofractionate corn gluten hydrolysates. The optimum conditions of gel filtration chromatographywere: flow rate45mL/h, sample concentration0.1g/mL, sample volume2mL. Three fractions(A1, A2and A3) were obtained under the optimum conditions, and the peak area ratios offractions were14.4%,17.9%and38.2%, respectively. The antioxidant activities of thosefractions were determined, and found out that A3has the best antioxidant activities.