Research On Membrane-based Separation And Manufacture Of Bioactive Serum Proteins From Goat Milk

Traditional industrial whey protein is a functional milk protein ingredient obtained by preparing cheese or by-product whey discharged from casein through acid precipitation or enzymatic precipitation.Whey protein has the characteristics of high nutritional value,easy digestion and absorption.However,the use of acids or enzymes and multiple heat treatments,such as pasteurization,spray drying at atmospheric pressure,etc.,have caused the loss of active ingredients in whey protein.Using membrane separation technology to separate whey protein from skimmed goat milk and combining ultrafiltration concentration and low-pressure spray drying technology to prepare bioactive whey protein powder.Compared with the by-product whey protein discharged from cheese prepared by traditional acid precipitation or enzyme precipitation,bioactive whey protein has not been acid coagulated or enzymatically coagulated,and retains the active structure of whey protein,contains more bioactive ingredients.It can improve the active ingredients of infant formula milk powder,functional protein products and health foods,and has broad application prospects.Therefore,the establishment of a membrane separation production process for bioactive whey protein is the key to realize the domestic industrial production of bioactive goat whey protein powder as soon as possible.This experiment uses goat milk as the raw material,the separation of whey technology by membrane technology as the main line,and uses ELISA,RP-HPLC,SDS-PAGE,SEM,proteomics and other methods to studied the sterilization effect of different sterilization methods on skim goat milk,effect of different membrane separation parameters on whey separation and effect of drying methods on goat whey protein powder.The main research contents and results are as follows:（1）Comparison of the results of large-aperture microfiltration sterilization,ultraviolet radiation sterilization,and high-temperature short-term sterilization:comprehensively comparing the removal rate of pathogenic bacteria and spores,the retention of bioactive protein and antibacterial enzymes,the retention of protein content,and the degree of protein oxidation.Using 1.4μm microfiltration to sterilize,the total number of colonies meets the national standard for pasteurized milk,and almost all somatic cells are intercepted.In terms of the retention of active ingredients,the retention rates of active IgG,IgA,IgM,Lf,LPO,and XO reached 87%,88%,94%,90%,97%and 72%respectively;the retention rate of whey protein was 93%,whey protein and casein are almost completely permeated;during the full filtration process,the membrane flux is stable at about 220 L·m^-2h^-1.（2）Comparison of the effect of microfiltration membrane pore size,concentration multiple,and diafiltration times on membrane separation of goat whey:comprehensive comparison of the permeability of active ingredients,the permeability of whey protein,membrane flux and other indicators.Using 100 nm ceramic membrane,3 times the concentration volume ratio diafiltration 3 times,the cumulative permeation of active IgG,IgA,IgM,Lf,LPO and XO are 73.97%,69.01%,56.6%,47.45%,38.65%and 24.17%,respectively.The permeability of whey protein in the permeate was 79.84%,and the average membrane flux during the full filtration process was 87.33 L·m^-2h^-1.（3）Using microfiltration separation technology to prepare membrane separation whey concentrate,acid method and enzymatic method to prepare acid whey concentrate and sweet whey concentrate:comprehensive bioactive protein and antibacterial enzyme content,protein content.In terms of active ingredient retention,low-pressure spray drying and freeze-drying have similar effects.In membrane-separated whey concentrate,the contents of active IgG,IgA,IgM,Lf and LPO are:1.00 g/100 g,86.38 mg/100 g,97.30 mg/100 g,247.81 mg/100 g and705 U/g;the protein content is 49.19%.The proteomics analysis of the three concentrates revealed significant differences between the three whey concentrates.The difference between membrane-filtered whey concentrate and sweet whey concentrate is relatively small,while the difference between acid whey concentrate and both is greater.（4）The membrane separation whey concentrate is prepared by low-pressure spray drying,atmospheric spray drying and freeze-drying methods to prepare whey protein powder.Acid whey concentrate and sweet whey concentrate are spray-dried to prepare acid whey protein powder,and compared with commercially available goat whey powder WPC50.Comprehensive comparison of bioactive protein and antibacterial enzyme content,physical and chemical indicators.The contents of IgG,IgA,IgM,Lf and LPO are 78.84 mg/100 g,10.37 mg/100 g,9.67 mg/100 g,45.95 mg/100 g and 43.33 U/g,respectively.The protein content is more than 90%,higher than commercial whey protein powder and acid/sweet whey protein powder.It has good protein solubility which reaching 99.63%.In summary,using 1.4μm ceramic membrane microfiltration sterilization can effectively remove microorganisms and somatic cells in skimmed milk,and can well retain the active ingredients in bioactive whey,with almost no protein retention;using 100nm ceramic membrane,3 times concentration,diafiltration 3 times separation parameters can better separate the whey protein and casein of goat milk,and retain more active ingredients in active whey;the whey concentrate and whey powder prepared by membrane separation technology and low-pressure spray drying can not only retain more the active ingredient,and has higher protein solubility.