Standardization of major constituents of bovine milk fat globule membrane

1.以牛乳为原料制备乳脂球膜（Milk fat globule membrane，MFGM），首先将脱脂奶油搅拌回收，然后将膜材料超滤浓缩，高温短时巴氏杀菌，最后冷冻干燥。磷脂主要由磷脂酰胆碱、磷脂酰乙醇胺和鞘磷脂组成。PAS-1、PAS-4、PAS-5、PAS-6、PAS-7和CB-1。3.为保证MFGM的质量，采用高温短时巴氏杀菌法对MFGM进行杀菌。为了检测巴氏杀菌的程度，测定了对高温短时巴氏杀菌稳定的FAD-焦磷酸酶和高温短时巴氏杀菌变性的碱性磷酸酶的活性。MFGM制剂中碱性磷酸酶失活，而FAD焦磷酸酶活性大部分保留，表明这些标记物是有用的。4.评价MFGM制剂的乳化能力。通过在Polytron均质器（19，000 rpm）上将1%MFGM和25%乳脂在磷酸盐缓冲液（pH 7.0）中的混合物搅拌（2 min）来制备乳液。结果表明，MFGM制剂制备的乳剂具有较高的乳化活性和稳定性，脂肪球的中位直径约为3-5 μ m。5.建议从MFGM组分的组成（磷脂和膜蛋白）、高温短时巴氏杀菌以避免变性、以及MFGM的乳化等功能。

1.Milk fat globule membrane (MFGM) was prepared from bovine milk in the following procedure, 1) washed cream was churned and buttermilk was recovered, 2) membrane materials were concentrated by ultrafiltration through membrane and pasteurized by high temperature-short time method, 3) finally MFGM was freeze-dried.2.Phospholipid and protein composition as a representative component of MFGM were measured by HPLC and SDS-PAGE,respectively. Phospholipid was composed of mainly phosphatidyl choline, phosphatidyl ethanolamine, and sphingomylin. Protein consisted of PAS-1, -4, -5, -6 and -7 and CB-1. These components were found in every MFGM preparations.3.For keeping the quality of MFGM preparation, MFGM was pasteurized by high temperature-short time method. For examinating the degree of pasteurization, the activity of FAD-pyrophosphatase which is stable for high temperature-short time pasteurization and of alkaline phosphatase which is denatured by high temperature-short time pasteurization were assayd. Alkaline phosphatase in the MFGM preparation was inactivated, whereas most of FAD-pyrophosphatase activity was kept, suggesting these markers are useful.4.Emulsifying ability of MFGM preparation was evaluated. Emulsion was prepared by homogenizing (2min) on Polytron homogenizer (19,000rpm) a mixture of 1% MFGM and 25% milk fat in phosphate buffer (pH7.0). It was found that emulsion made by MFGM preparation had a higher emulsifying activity and emulsion stability and the median diameter of fat globule was about 3-5 mum.5.It was recommended that MFGM preparation might be evaluated from three points of composition of MFGM constituents such as phospholipid and membrane protein, pasteurization by high temperature-short time method in order to avoid the denaturation, and function of MFGM such as emusification.