冻融处理对豆浆中7S和11S蛋白分离的影响

Effect of Freeze-Thaw Treatment on the Fractionation of 7S and 11S Globulins in Soymilk

采用冷冻-融化方法处理豆浆,探讨不同因素对冻融处理后的豆浆中7S和11S大豆球蛋白分离的影响,以11S/7S比值作为评价指标。结果表明:冻融处理可以促使豆浆分层,大部分7S蛋白聚集在上清液而11S蛋白聚集在下层液中,实现粗分离。脱脂豆浆呈现出与未脱脂豆浆相似的分层现象,其上下层溶液中11S/7S比值差异均不显著(P>0.05)。但是无论脱脂与否,离心操作均会进一步增加11S蛋白在下层液中的累积。亚硫酸钠或十二烷基硫酸钠的添加均会影响冻融后豆浆的分层,且0.1%(m/v)的亚硫酸钠即可抑制7S和11S蛋白的分离。综上所述,可推测出这种分离是由于11S球蛋白和/或11S球蛋白与油脂复合物形成不溶性聚集物的选择性沉淀,其中的蛋白质分子通过二硫键和/或疏水相互作用聚集在一起。

The freeze-thaw method was used to treat soymilk and to explore the effects of different factors on the separation of 7S and 11S soy globulin in the freeze-thaw treated soymilk,with the 11S/7S ratio as the evaluation index.Results showed that freeze-thaw treatment induced stratification of soymilk,with most of the 7S proteins aggregating in the supernatant solution while 11S proteins aggregated in the lower solution,achieving coarse separation.The defatted soymilk showed similar stratification as the non-defatted soymilk,and the 11S/7S ratios in both the upper and lower solutions were not significantly different compared to each other(P>0.05).However,the centrifugation operation further increased the accumulation of 11S protein in the lower solution,regardless of whether it was defatted or not.The addition of either sodium sulfite or sodium dodecyl sulfate affected the stratification of soymilk after freezethawing,and 0.1%(m/v)of sodium sulfite alone inhibited the separation of 7S and 11S proteins.Thus,this fractionation is due to selective precipitation of aggregates of 11S globulins and/or 11S globulins and lipid complexes,in which the protein molecules interact through disulphide bonds and/or hydrophobic interactions.