Development And Characterization Of Quinoa Polypeptide Complex Functional Drink

Quinoa（Chenopodium quinoa Willd）is rich in protein,starch and dietary fiber,but also rich in micronutrients and functional active ingredients,such as calcium,magnesium,zinc,vitamin E,folic acid,polyphenols,flavonoids,saponins,etc.,high nutritional value.Quinoa protein is the second largest nutrient in quinoa,its content is up to 14%～17%.Quinoa protein is a high-quality plant protein with high nutritional value.It contains all the essential amino acids needed by human body,and the ratio of amino acids is balanced.Quinoa peptides obtained by hydrolysis of quinoa protein also have rich bioactive functions.However,there are few studies on the use of two enzymes to hydrolyze quinoa protein.The limited hydrolysis ability of a single enzyme makes the hydrolysis incomplete and reduces the bioavailability of quinoa protein.At the same time,a single enzyme has a certain steadiness to the hydrolysis of protein and only acts on a fixed cleavage site,so the yield of polypeptide is low.In addition,quinoa protein is less soluble,which also limits its use in the food industry.Therefore,in this study,alkali extraction combined with enzyme hydrolysis technology was adopted to improve the yield of quinoa protein,while retaining other water-soluble nutrients and functional active ingredients,so as to improve the bioavailability of quinoa protein.Quinoa protein was hydrolyzed by compound enzyme to prepare quinoa peptide,which improved the solubility of quinoa protein and made quinoa peptide have higher functional activity.Finally,quinoa polypeptide,supplemented by Tartary buckwheat flavonoid,barleyβ-glucan as stabilizer made a natural drink rich in various functional characteristics.The main research results are as follows:1.The high protein quinoa variety-HL was used as raw material,the protein was extracted by alkali extraction enzyme assisted method,and the high antioxidant activity trypsin and flavor protease were selected to hydrolyse quinoa protein proportively.The response surface method was used to optimize the hydrolysis process of quinoa protein by complex enzyme based on the single factor test.The results showed that the optimal conditions of complex enzymatic hydrolysis were as follows:substrate concentration of 2mg/m L,enzyme ratio of 3:2（trypsin:flavor protease）,enzyme dosage of 2.0%（w/w）,enzymatic hydrolysis time of 4 h,enzymatic p H 7.5,enzymatic hydrolysis temperature 50℃,the antioxidant activity of 35.758%.2.The physicochemical properties of quinoa polypeptide were analyzed.The results showed that the molecular weight of quinoa polypeptide was mainly distributed in the range of 0.8～3.0 KDa.Compared with quinoa protein,quinoa polypeptide was more easily digested and absorbed by human body,and its amino acid content increased from 11.189 g/100g to74.170 g/100g.In addition,compared with quinoa protein,it has better foaming property,foam stability,emulsifying property and emulsifying stability.Foaming property increased from 49%to 75%,foam stability increased from 75%to 89%,emulsifying property increased from 45%to 72%,and emulsifying stability increased from 73%to 92%.The solubility of quinoa polypeptide was better than that of quinoa protein.The solubility of quinoa polypeptide was increased from 65.93%to 85.26%under neutral condition,indicating that the solubility of quinoa protein was improved after enzymolysis.The digestive characteristics of quinoa peptides showed that there was no significant change in the antioxidant activity of quinoa peptides in the stomach environment.The antioxidant activity of quinoa peptides was increased to a certain extent at the beginning of the intestinal environment,but then stabilized,indicating that the gastrointestinal environment had little influence on quinoa peptides and could maintain good antioxidant activity in the stomach.At the same time,it was found that the antioxidant capacity of quinoa peptide and quinoa protein showed some differences,the antioxidant capacity of quinoa protein was significantly lower than quinoa peptide,the most significant is the ABTS free radical scavenging ability,with the continuous increase of the concentration of antioxidant activity,the scavenging capacity was close to 100%at 1.6mg/m L.And,the scavenging ability of the two substances on free radicals was DPPH>OH>ABTS>O₂^-.3.Based on the physicochemical properties of quinoa polypeptides,a functional drink was prepared.Quinoa polypeptides were used as the main functional substances and Tartary buckwheat flavonoid and barleyβ-glucan were used as the assistant functional substances and stabilizing agents.The mixing process of the drink was optimized.The optimum formulation of quinoa polypeptide complex functional drink was obtained by L₉（3⁴）orthogonal test.The results showed as follows:0.1%aspartame aqueous solution supplemented with 5%,Tartary buckwheat flavonoid supplemented with 0.3%,barleyβ-glucan supplemented with 0.5%,quinoa polypeptide supplemented with 1:10,the beverage sensory score was the highest,the highest score was 88.15.4.The quality analysis of the drink shows that the stability of the drink is better,which the best way to store is in a cool place away from light.It is not recommended to store it in cold storage for a long time.Based on the determination of volatile substances in drinks by GC-MS,152 kinds of volatile substances were determined,including 34 kinds of acids,33kinds of alcohols,28 kinds of esters,22 kinds of alkanes,16 kinds of aromatics,8 kinds of halogenated hydrocarbons and 11 kinds of other kinds.Finally,the functional characteristics of quinoa polypeptide complex functional drinks were analyzed.The results showed that compared with commercially available functional drinks,Quinoa polypeptide complex functional drinks showed antioxidant capacity（O2 scavenging capacity 96.60%,DPPH scavenging capacity 95.67%,OH scavenging capacity 98.73%,ABTS scavenging capacity91.01%）,adsorption bile salt（68.12 mg/m L）,cholesterol（16.65 mg/m L）,sodium cholic acid（26.05）mg/m L),glucose（16.36 mmol/L）,cation exchange ability and inhibition of pancreatic lipase activity（29.66%）showed good results,which also indicated that there was a certain synergistic effect among the functional substances.