Study On Preparation Technology And Workshop Design Of Quinoa Polypeptide And Beverage

Quinoa is rich in starch,proteins,dietary fibers and micronutrients,including polyphenols,saponins,vitamins and minerals.The content of proteins in quinoa reach up to 14%～17%,higher than that in rice,barley and corn.Quinoa proteins have high nutritional value,because they contain all the essential amino acids needed by the human body,and possess balanced amino acid composition.However,few studies on the industrial extraction method of quinoa protein were reported.The traditional alkaline extraction and acid precipitation method used for the extraction of quinoa proteins had a low protein yield,and the other water-soluble nutrients were lost,leading to a waste of quinoa resources.Meanwhile,in this process,large amounts of acid and alkali were used,resulting in environmental pollution.In addition,the poor solubility of quinoa proteins also limits their application in food industry.Therefore,in this study the alkaline extraction combined with membrane separation was used to improve the yield of quinoa proteins,and other water-soluble nutritional components were retained,which could be further used for development of soft beverages,improving the application value of quinoa.And then the quinoa proteins obtained were treated by enzymatic hydrolysis to improve their solubility,and the quinoa peptides formed showed higher antioxidant activity.Finally,the design of quinoa production workshop was completed to confirm the feasibility of industrialization of these processes mentioned above.The main research contents of the thesis are as follows:The dehulled quinoas was used as raw materials and the alkaline extraction combined with membrane separation was used to extract quinoa proteins.Results showed that the optimal conditions of the alkali extraction process were: temperature 35 °C,time 3 h,Na OH concentration 1 g/L,solid-liquid ratio 1:10.Effects of PES50 and PES5 ultrafiltration membranes on separation efficiency of proteins were further investigated and results indicated that PES50 ultrafiltration membranes had better separation efficiency and higher membrane flux.The retention rate of proteins and polysaccharide was 95.58% and 13.20%,respectively,and the final yield of proteins was 81.24%.After the extraction of quinoa proteins under the optimal conditions,the effect of enzymatic hydrolysis on the yield of quinoa peptides,antioxidant activity,amino acid composition,nutritional value and digestive properties was investigated.With antioxidant activity and nitrogen recovery rate(NRR)as indicators,the optimal conditions of enzymatic hydrolysis were obtained that enzyme type was compound protease,substrate concentration was 6%,enzyme addition amount was 1800 U/g,and reaction time was 4 h.Under these conditions,the yield of quinoa peptide was 76.51%,and they had good antioxidant activity.Under neutral conditions,the solubility of quinoa protein increased from 66.16% to 90.71%.And the results of in vitro simulated digestion properties of quinoa peptides indicated that they could maintain good antioxidant activity in the intestines and stomach phase.Analysis on amino acid composition and molecular weight distribution suggested that the quinoa peptides had balanced amino acid composition and primarily consisted of oligopeptides(<2 k Da),accounting for 74.00%.The by-products filtrate separated after the ultrafiltration process of quinoa protein were used as raw materials to produce quinoa beverage and the clarity reached 96.90%.The optimum formula of the beverage was obtained: the amount of citric acid was 0.15% and xylitol was chosen as a sweetener at 5%.Results on storage stability analysis of quinoa beverage showed that stored in a cool and dark place,they could maintain the clarity and pigment stability for a long period.Based on the research on the production process mentioned above,the workshop of quinoa with annual processing capacity of 1000 tons was designed.The production line had a high degree of automation,and it could produce 99.45 tons of quinoa peptides and 6,900 tons of quinoa beverages per year,which was of great economical value and social value.