Functional Properties Of Protein Prepared From Juglans Mandshurica Maxim Kernel And Antioxidant Activity Of Its Enzymatic Hydrolysate

Juglans mandshurica Maxim kernel is rich in nutrients, is beneficial to body for long-termconsumption, and its protein content is second only lower than oil content, so property ofprotein is of great significance. This study was designed to develop and utilize Juglansmandshurica Maxim protein resources, to improve the Juglans mandshurica Maxim economicvalue.This paper studied Juglans mandshurica Maxim kernel protein isolate which was preparedusing the alkaline dissolving and acid precipitating method and Juglans mandshurica Maximkernel defatted meal as raw materials. First with Bradford method measured the supernatantresidual protein content and determined pH of acid precipitating was4.9. Then by single factorexperiments investigated the affect of pH, temperature, time and solvent ratio for Juglansmandshurica Maxim kernel protein isolate extraction efficiency and purity. Ultimately byorthogonal test determined the optimal extraction conditions were follows: the extraction pH9.0,temperature55℃, solvent ratio1:14, time90min.Juglans mandshurica Maxim kernel protein isolate prepared using the alkaline dissolvingand acid precipitation method and albumin, globulin and glutelin obtained by Osborne methodwere investigated for their functional properties. Protein contents of albumin, globulin, glutelinand the protein isolate were determined to be31.47%,53.89%,89.32%and91.35%,respectively. The protein solubility map displayed the lowest solubility of these proteins were atpH5.0. Water holding capacity and oil holding capacity were, respectively,2.76mL/g and2.02mL/g for glutelin, which were significantly higher than the values of1.19mL/g and1.8mL/gfor albumin,0.63mL/g and1.79mL/g for globulin,2.27mL/g and1.44mL/g for protein isolate.Sulfhydryl content of albumin and globulin were higher than that of glutelin and protein isolate,the highest of disulphide content was121.690μmol/g for globulin. Foaming capacity, emulsionability and emulsion stability of these proteins performed the lowest values at pH5.0, while thefoaming stability were the most stable, just the opposite.Through amino acid analysis we can see, Juglans mandshurica Maxim kernel albumin,globulin, glutelin and protein isolate were rich in Glutamine acid and Arginine, meanwhile theseproteins contained all the essential amino acids. SDS-PAGE profile indicated that the majormolecular weight (MW) of albumin were19-21kDa and30-32kDa, the important MW ofglobulin were18.5-22kDa,30-33.5kDa and49-56kDa, glutelin had many bands, the main MW were19-21kDa,44-58kDa, and several independent minor MW were22,23,29.9,33,35and44kDa, the MW of protein isolate about were23,25,29.9,33.5,44.3,48,55and58kDarespectively.With protein isolate from Juglans mandshurica Maxim kernel as the raw material, thispaper was designed to study the optimum hydrolysis technology condition and antioxidantactivity of antioxidant peptide, to provide experimental data and theoretical basis for furtherprocessing of Juglans mandshurica Maxim protein. On the base of single factor experiment,Box-Benhnken methodology was applied to optimize the hydrolysis conditions (includingenzym pH, enzymolysis temperature, enzyme dosage, and substrate concentration) withreducing power ability as index. The optimum conditions are as follows: pH of7.6, substrateconcentration of4.6%, enzyme dosage of4510U/g, enzymolysis temperature of50℃, and timeof4h. On this condition, the reducing power ability was0.346, the degree of hydrolysis was16.50%.The results of antioxidant tests showed that scavenging activity on ABTS, DPPH, hydroxylradical and superoxide anion radical and reducing power ability increased with increasingenzymatic hydrolysate concentration. The scavenging activity of enzymatic hydrolysate onABTS and DPPH was100%and90.08%of Vc at0.8mg/mL and1.2mg/mL, the reducingpower ability was68.61%of Vc at6mg/mL, the scavenging activity on hydroxyl radical andsuperoxide anion radical was94.56%and46.51%of Vc at15mg/mL. These demonstrated thatthe scavenging activity of enzymatic hydrolysate on ABTS and DPPH are strong, thescavenging activity on hydroxyl radical and superoxide anion radical and the reducing powerability are weaker than those of Vc.