Enzymatic Demulsification Research Of Emulsion Formed During Aqueous Extraction Of Peanut Oil

Peanut is one of the most important supply resources of edible oil and protein in ourcountry even the world.Aqueous extraction can extract peanut oil and protein synchronouslywhich has attracted much attention,but it has not been realized industrialization for theproblem of demulsification difficulty and high energy consumption.As a new biologicdemulsification method,enzymatic demulsification has a good development and applicationprospects.But now there is still a lack of systemic and in-depth research of enzymaticdemulsification.We optimized the aqueous extraction process of peanut oil and proteinsynchronously,the optimization of enzymatic demulsification process,the demulsificationcourse and mechanism,the quality of demulsified oil were studied.The specific results were asfollows:Firstly,the optimal conditions of aqueous extraction process of peanut oil and proteinwere as follows:ratio of solid to liquid1:10,alkaline extraction pH11.0,alkaline extractiontemperature40℃,alkaline extraction time1.5h.Under these conditions,the extraction ratio ofoil could be reached to96.21%,the extraction ratio of protein could be reached to89.91%.Pelling off peanut or not had no significant influence on the extraction ratio of oil andprotein.Then enzymatic demulsification process were studied through two different grindingways.For the emulsion formed during dry grinding,the optimum demulsification enzyme wasalkaline protease2709,the optimal demulsification conditions were as follows:ratio ofemulsion to water1:1.1,enzyme concentration0.50%(w/w),temperature55℃,pH8.5,hydrolysis time70min.Under these conditions,the demulsification ratio of the emulsionreached or exceeded90%.For the emulsion formed during wet grinding,the optimaldemulsification conditions of the alkaline protease2709were as follows:ratio of emulsion towater1:1.1,enzyme concentration0.60%(w/w)(1600IU/g emulsion),temperature55℃,pH8.5,hydrolysis time70min.Under these conditions,the demulsification ratio of the emulsionreached93%.Phospholipase A2could demulsify the emulsion formed during dry grindingeffectively,but to the emulsion formed during wet grinding,it could hardly work.pH hadalmost no influence on the stability of the emulsion formed during wet grinding.For the emulsion formed during wet grinding,the demulsification ratio and the degree ofhydrolysis had a highly significant positive correlation to each other in demulsificationprocess(r=0.96,a=0.01);the enzymolysis process of emulsion was studied through imageparticle analysis system:as the hydrolysis time increased,small oil drops of the emulsion reduced and large oil drops increased gradually,the total number of oil drops decreased andthe average diameter of those increased gradually;the protein wrapping on the surface of oildrops and the change of oil drops before and after enzymolysis were observed throughfluorescence microscopy:before enzymolysis,the oil drops of emlsion were small and had alarge number,distributed densely, but after enzymolysis,the oil drops of emulsion turned to belarge and had a small number,distributed separately. Many oil drops became irregular shapeduring enzymolysis.Finally,the quality of demulsified oil was studied throughenzymatic,freezing-thawing,heating ways to break the emulsion formed during wetgrinding.The result indicated that the ways of demulsification had little influence on themoisture and volatile substances,insoluble impurities,acid value,saponificationvalue,refractive index,but a large influence on the peroxide value and color:the color ofheating demulsified oil was deepest and that of enzymatic demulsified oil andfreezing-thawing demulsified oil were lighter;the peroxide value of enzymatic demulsified oilwas the smallest and the oxidative stability was the best,peroxide value of heating demulsifiedoil was the biggest and its oxidative stability was the worst;the enzymatic demulsified oilcontained the largest content of total VEand α-component.Not only the enzymaticdemulsification process was clean and efficient,but also the quality of demulsified oil couldbe good.These advantages would improve aqueous extraction process of vegetable oil andprotein.