Proteolysis Of Wheat Germ Albumin And Antioxidant Activity Of The Hydrolysate

Wheat germ is a high-quality plant protein source of which about 30% nutrient belongs to protein.Wheat germ protein is mainly composed of albumin,globulin and gliadin.Wheat germ albumin is the most protein in wheat germ,also with the best amino acid composition.Furthermore,wheat germ albumin can be extracted by water extraction.In this paper,wheat germ albumin was extracted primarily,then the optimum conditions were explored.The effects of DH on the hydrolysates' functional characteristics and antioxidant activity were studied.The hydrolysate with appropriate DH was separated and purified,followed by amino acid composition analysis.The main conclusions are as followed:(1)Wheat germ albumin is a high-quality protein with rich and balanced amino acids.SDS-PAGE showed that wheat germ albumin was composed of several protein subunits with the molecular weight of 14.61,19.49,24.77,30.02,48.51,67.88 and 82.22 k Da,indicating that the majority of wheat germ albumin possess high molecular weight.(2)The optimal enzyme for wheat germ albumin is alkaline protease.The hydrolysis conditions for optimal DH were: E/S=8000U/g,c=2%,p H=9.1,t=2h,T=60?,with the DH of 9.32%.(3)The wheat germ albumin hydrolysates with different DH were prepared under the optimum conditions.The solubility of the hydrolysate was improved after hydrolysis.The higher the DH,the better the solubility was.The solubility at the soelectric point increased from 49.52% to 74.09% when the DH was 0 and 8.34%,respectively.The emulsifying properties decreased with the increase of DH.When the DH was lower than 7.54%,the DPPH radical-scavenging activity and hydroxyl radical-cavenging activity of the hydrolysates increased with the DH.When the DH was 7.54% and the concentration was 100 mg/m L,the DPPH radical-scavenging rate and the hydroxyl radical-cavenging rate were 59.68% and 50.23%,respectively.(4)The wheat germ albumin hydrolysate with hydrolysis time of 60 min was divided into two fractions by ultrafiltration tube firstly,the molecular weight of >3k Da and ?3k Da,in which the fraction of ?3k Da possesses higher free radical scavenging rate.The optimum separation conditions of Sephadex G-25 gel chromatography were determined: eluted with deionized water,1 m L/min elution speed,100mg/m L of sample concentration,and 1.0m L sample.Wheat germ albumin hydrolysate could be separated into three peaks(F1,F2,and F3),and each peak had the ability to scavenge free radicals.The third peak(F3)had the best radical scavenging activity,and the radical scavenging rates of F3 to DPPH?,OH? and O2-? were 73.98%?46.21% and 89.74% respectively.The F3 peak was analyzed by Ultra Performance Liquid Chromatography(UPLC).The map shows that the F3 peak was not a single substance and could be divided into four component peaks.The amino acid analysis results showed that the amino acid content of F3 peak was high,which was mainly composed of Glu,Asp,Leu,Phe and so on with antioxidant activity.