Preparation And Characteristics Of Bioactive Peptides From Hydrolyzing Extruded Corn Protein Meal

Corn gluten meal was used as raw material,which was modified by means of extrusion.2709alkaline protease was chosen as the enzyme of corn gluten meal.Barrel temperature, rotation speedof screw and die diameter of extruding machine and the water content in raw material wereconsidered as factors; peptide yield was employed as evaluation index. With the aid of thequadratic orthogonal rotation design with five factors, the regression equation was established andthe analysis of factors was proceeded and the process conditions was optimized by responsesurface methodology. The results indicate that the optimal extrusion conditions are material watercontent of25.5%,barrel temperature of82℃,die diameter of8mm, rotation speed of182r/min.Under the optimal conditions, the peptide yield is up to78.48%.Scanning electron microscope observation indicated that the size and shape of microstructureof raw corn protein were random,and the Surface was uneven which appeared to be a very closedstate.In contrast,the tight structure of extruded corn protein wae unfolded,the sags and crests ofsurface became intensified, Specific surface area increased and hole structures can be observed,allthat were benefit for enzymolysis.According to the SDS-PAGE electrophoresis, we found that themolecular weight of corn protein did not change significantly with and without extrusion.comparedthe infrared spectroscopy of zein,corn alkali soluble protein,corn salt soluble protein and cornwater soluble protein with and without extrusion,the group changing was found.2709alkaline protease was used as the enzyme of extruded corn gluten meal,withenzymolysis temperature,enzyme concentration,the reaction time and pH as the investigationelements,degree of hydrolysis was and total antoxidative capacity as hydrolysis index.Single factorand the orthogonal test of four factors at three different levels were used to study enzymolysiseffect.The results show that the ideal condition was as follows:PH=10,additive amount of proteasewas13%, hydrolysis temperature was55℃,and hydrolysis time was4h.Under the condition,thedegree of hydrolysis was31.95%and total antoxidative capacity was1.15U/mg.Corn protein hydrolysate was desalted by using DA201-C macroporous adsorption resin.It’sprocess conditions were as follows:pH for corn protein hydrolysate was8,concentration ofpeptides was30mg/ml,flow rate of2BV/h,alcohol with75%concentration as desorptionagent.Under these conditions,the recovery of corn peptides was about79.67%and the desalted ratereached to90.10%.the result suggested that the desalination method by using DA201-Cmacroporous adsorption resin applied to corn polypeptides was a simple and available method. solubility,viscosity,foaming and foam stability and Amino acid composition of freeze-driedcorn peptides after desalination was measured.Corn peptides were purified by using ultrafiltration centrifugal method in order to get highoxidation relatively component(MW<3KDa).The molecular weight of corn polypeptide wasdetermined by Sephadex G-25gel chromatography and antioxidant activity of hydroxyl radicalscavenging ability,superoxide anion radical scavenging ability,DPPH radical scavengingability,anti-lipid peroxidation ability and Iron ion reduction ability were discussed.