牦牛乳脂肪球膜组成分析及蛋白热稳定性

摘要

为分析牦牛奶脂肪球膜（MFGM）的组成及探讨其蛋白的热稳定性,采用物理方法从牦牛奶脂肪中提取分离MFGM.结果发现在分离过程中KCl溶液洗涤次数较关键,洗涤3次较适宜.牦牛MFGM主要由蛋白质（26.93%）和脂类（70.34%）两大物质组成,还含有少量的己糖、唾液酸和灰分.牦牛MFGM蛋白的主要氨基酸是谷氨酸、亮氨酸、丝氨酸和赖氨酸,其中必需氨基酸占整个氨基酸的49.48%.当加热温度达60℃时,MFGM蛋白特别是黄嘌呤氧化酶（XO）、过碘酸稀夫6（PAS6）和过碘酸稀夫7（PAS7）损失较大.而β-乳球蛋白和α-乳白蛋白在此温度下与牦牛MFGM开始发生结合,MFGM蛋白属于热不稳定蛋白。%To analyze the component and protein heat stability of yak milk fat globule membrane(MFGM),physical method was used to extract and separate MFGM from yak milk fat.The results show that the wash times to separate MFGM is very critical,and the optimum wash time is three.The yak MFGM mainly contains protein(26.93%) and lipids(70.34%),and there are other minor components in MFGM such as hexane,sialic acid and ash.The predominant amino acids in yak MFGM are Glu,Leu,Ser,Lys and Vla,and among these amino acids,the essential amino acids account 49.48% of total amino acids.When heated to 60 ℃ the MFGM protein,especially for xanthine oxidase(XO) and Periodic acid Schiff 6/7(PAS6/7),lose markedly.However,the SDS-PAGE under reducing conditions shows that the β-lactoglobulin and α-lactalbumin begin to associate with the MFGM at 60 ℃ the MFGM protein is heat unstable protein.