为了探寻大豆分离蛋白(SPI)在长期贮藏过程中溶解性不断下降的原因,文中研究了SPI中微量油脂存在的影响。制备了SPI、含2%未氧化大豆油SPI和含2%氧化大豆油的SPI 3组样品,采用真空包装,在贮藏12周过程中定期测定样品的溶解度、蛋白羰基、表面巯基、总巯基以及自由氨基等性质。结果表明:在贮藏过程中所有SPI的溶解性均有不同程度的降低,其中含油脂氧化的样品SPI溶解度的下降最快且溶解度最低。3组样品在贮藏期间的羰基、总巯基、自由氨基含量变化几乎无差别,但空白SPI的表面自由巯基含量始终高于含有未氧化大豆油的SPI和含氧化大豆油的SPI(P<0.05)。说明大豆蛋白贮藏期间发生了氧化反应,氧化油脂可以促进溶解度下降的加速,但是氧化油脂本身不是导致蛋白质氧化的唯一影响因素,导致大豆蛋白贮藏过程溶解度下降的原因比较复杂,需要进一步深入研究。

This paper studies trace lipid's impact on the solubility decrease of soy protein isolate(SPI) in long-term storage.Three groups of SPI sample including SPI control,SPI with 2% non-oxidized soybean oil,and SPI with 2% oxidized soybean oil were prepared and sealed by vacuum.During 12 weeks storage,solubility,protein carbonyl content,surface free sulfhydryl group content,total sulfhydryl group content,and free amino group content were tested.It showed that the solubility of three groups decreased in a varied way: solubility of SPI with 2% non-oxidized soybean oil decreased the fast and its final solubility was the lowest in three groups.There was no significant difference in protein carbonyl content,total sulfhydryl group content,and free amino group content during storage,but surface free sulfhydryl group content of SPI(control) was constantly higher than other two groups.Results indicated that protein oxidation occurred in SPI during storage,oxidized oil speeded up the solubility decrase.However,oxidized oil was not the only factor affected protein oxidation.The main factor which caused the decrease of solubility needs to be further studied.