Extraction Of Quinoa Protein And Improvement Of Its Functional Properties

As a quality protein,the average content of quinoa protein can reach to 12%-23%,and quinoa protein contains 8 essential amino acids with homogeneous proportional,which are easy to be absorbed by the human body.It has been more and more widely used in food processing because of its high nutritional value and functional properties.However,there are few researches on quinoa protein extraction optimization and improvement of its functional properties.In this study,dual-enzymatic hydrolysis assisted ultrasonic technology were selected to extract protein from dehulled quinoa.Under the condition,we used microbial transglutaminase to catalyze the glycosylation cross-linking reaction of quinoa protein and chitosan oligosaccharides,to research the effects of glycosylation modification on the antioxidant activity of quinoa protein.At the same time,we used ultra high pressure technology to treat quinoa protein,and the effects of ultra high pressure on emulsifying property of quinoa protein was studied.In order to provide theoretical reference and experimental basis for the application of quinoa protein in food industry.The specific research content and experimental results were as follows:Firstly,using the extraction rate of quinoa proteins as index,fixed the ratio of cellulose and glucoamylase,on the basis of single factor test,response surface test was used to optimize the process conditions of extraction of quinoa protein by dual-enzymatic hydrolysis with ultrasound.The optimum extraction conditions were obtained as follows:the ratio(cellulose:glucoamylase)of 4:6,enzymatic hydrolysis time of 71 min,enzymatic hydrolysis temperature of 50?,pH value of 5.0,total enzyme dose of 427 U/g,under the conditions,the extraction rate of quinoa proteins was 76.82%.The SDS-PAGE analysis showed that quinoa protein had main subunits with molecular weights of 50,32?39,22?23 and 8?9 kDa.Secondly,the grafting degree,DPPH free radicals scavenging activity,hydroxyl free radicals scavenging activity,the total reduction capacity and ferrous chelating ability were used as indexes,and reaction conditions of the glycosylation were optimized by single factor trials,to research the effects of glycosylation modification on the antioxidant activity of quinoa protein.The optimized reaction conditions as following:molarratio of acyl donor/acceptor of 1:2,quantity of TGase added of 60U/g protein,reaction time of 5 h,reaction temperature of 45?and pH value of 7.0.Under the conditions,the grafting degree,DPPH free radicals scavenging activity,hydroxyl free radicals scavenging activity,the total reduction capacity and ferrous chelating ability of glycosylation products reached to 45.00%,66.00%,82.00%,0.69and 53.00%respectively.The DPPH free radicals scavenging activity,hydroxyl free radicals scavenging activity,the total reduction capacity and ferrous chelating ability of unmodified quinoa protein were 38.00%,46.00%,0.12 and 5.00%respectively.Compared with unmodified quinoa protein,the antioxidant activity of glycolylation modified quinoa protein was significantly improved.Thirdly,using the emulsifiability of quinoa protein as index,on the basis of single factor test,the response surface test was used to optimize the conditions of ultra high pressure technology to treat quinoa protein.The optimum conditions were obtained as follows:the pressure of 235 MPa,the holding pressure time of 5.2 min,the protein mass fraction of 0.34%,under the conditions,the emulsifiability of quinoa protein was 119.00 m~2/g.Compared with unmodified quinoa protein(the emulsifiability of72.50 m~2/g),the emulsifying property of quinoa protein after ultra high pressure treatment was significantly improved.