Isolation Of Soybean Oil Body Concentrate And Its Functional Properties

Soybean contains approximately 40%protein and 20%lipid,which are respectively stored in protein storage vacuoles（PSVs）and oil bodies（OBs）.By grinding soaked soybean,soybean cells and PSVs are disrupted,proteins and OBs are released into aqueous phase.By filtering and subsequent processing,soymilk,tofu,and yuba can be obtained.However,the price of these products is low,which is not beneficial for the development of company.By referring to the processing of low-fat milk,one foreign company released soymilk cream and low-fat soymilk by using patented technology,which have high prices.However,this technology needs high requirement for centrifuge equipment and operators,and at the same time,it is a patented technology.These make domestic companies difficult to process similar products.This study would firstly adjust the aqueous conditions of soymilk to make OBs and proteins aggregate to form OB-protein aggregates,and then separate these aggregates from the other nonaggregated proteins by low centrifugal force.Thus,this study contains the following contents:1)examining the effects of soymilk systems and pretreatment on separation of OB concentrate;2)the mechanism of precipitation of OBs;3)the functional properties of OB concentrate.The detailed contents and results are as follows:Firstly,the effects of different soymilk systems and pretreatment on separation of OB concentrate were examined.For the efficient separation condition of soybean OB concentrate,the yield of OB concentrate and the OB content in OB concentration were comprehensively considered.The results showed that the efficient condition was to adjust the pH of raw soymilk（soaked 4℃,18 h）,and OB concentrate could be obtained by low-speed centrifugation.In this condition,the effects of pH 6.1⁵.4 on the formation of OB-protein aggregates were examined.The results showed that at pH 5.9,approximately 10 g of OB concentrate could be obtained from 100 g of raw soymilk,and the OB concentrate contained approximately 22%solid,10%OB,and 10%protein.Correspondingly,90 g of low-fat soymilk could be obtained from 100 g of raw soymilk,and its solid,protein,and lipid contents were respectively 3.7%,1.6%,and 0.4%（original raw soymilk contained 5.6%solid,2.5%protein,and 1.4%lipid）.Secondly,the mechanism of acidic pH-induced precipitation of OB-protein aggregates was examined via particle size analysis,SDS-PAGE and theoretical calculation of OB density,which could be used to explain the results above.The smaller the size of OBs was,the more easily the OB-protein aggregates were precipitated.In addition,the results also revealed that OBs with similar size showed different behaviors at the same pH,some precipitated,and the other still remained in the supernatant.This should be induced by the absorbed protein components in OB-protein aggregates:OBs in raw soymilk absorbed proteins randomly,when they absorbed high ratio of 11S,its density would be larger than those which absorbed high ratio of 7S.Finally,the processing properties of OB concentrate were examined.1)the effects of pH and coagulants（CaSO₄,MgCl₂,and GDL）on gelation of OB concentrate were examined.The results showed that good gel could be obtained in two conditions:pH 6.7 in a water bath at90°C for 1 h or addition of 0.2%CaSO₄ in a water bath at 70°C for 1 h.2)examining the oil-emulsifying amount of OB concentrate and the effects of pH,NaCl,and preparation order（emulsifying and subsequent acidic pH adjustment,acidic pH adjustment and subsequent emulsifying）on the emulsifying ability.The results showed that OB concentrate could emulsify the same amount of soybean oil;at pH 6.0,the OB concentrate-oil emulsion showed the highest viscosity;NaCl could decrease the viscosity of OB concentrate-oil emulsion,emulsifying and subsequent acidic pH adjustment was beneficial for the viscosity of OB concentrate-oil emulsion.3)the effects of NaCl,pH,and sucrose ester on foaming property of OB concentrate were examined.The results showed that the best foaming property was obtained in the conditions of 6%NaCl and pH 6.0,and the foams were delicate.This paper clarified the proper separation conditions and separation mechanism of soybean OB concentrate,and further,examined its processing properties,which supplied a new strategy for soybean processing,and was beneficial for the development of soybean industry.