Rombaut R, Dewettinck K
Laboratory of Food Technology and Engineering, Department of Food Safety and Food Quality, Faculty of Bioscience Engineering, Ghent University, Belgium.
J Dairy Sci. 2007 Jun;90(6):2665-74. doi: 10.3168/jds.2006-711.
Fragments originating from the milk fat globule membrane (MFGM), which is rich in polar lipids and membrane-specific proteins, are gaining interest for their functional and nutritional properties. Acid buttermilk cheese whey was used as a source for MFGM purification, because its MFGM content is more than 5 times higher than that of standard rennet whey. Because polar lipids are the main constituent of the MFGM and only occur in membranous structures, the polar lipid content was taken as a parameter for the total MFGM fragment content. The process of thermocalcic aggregation was evaluated on its recovery of MFGM fragments in the pellet. This method, originally intended for whey clarification and defatting, is a combination of calcium addition, a pH increase, and a thermal treatment. The influence of pH (6.5 to 8), temperature (40 to 70 degrees C), and calcium concentration (0.1 to 0.24 g/100 g) on the pellet mass and dry matter (DM) content and on recovery of protein and polar lipids (and thus indirectly on MFGM fragments) was investigated by means of a response surface Box-Behnken orthogonal design. Reduced quadratic models were fit to the experimental data and were found to be highly significant. No outliers were observed. The recovery of MFGM fragments was found to be highly dependent on the pH, and less dependent on temperature and calcium addition. Next to MFGM proteins, whey proteins were also found to be involved in the formation of aggregates. Optimal conditions were found at 55 degrees C, pH 7.7, and 0.205 g of calcium/L of whey. Under these conditions, 91.0% of the whey polar lipids were recovered in a firm and compact pellet of only 7.86% of the original whey mass, with a polar lipid concentration of 8.34% on pellet DM. Washing with water and centrifugation of the pellet was successful because after one washing step, virtually all sugars were removed, whereas 75.9% of the whey polar lipids could still be recovered. As such, the polar lipid content of the washed pellet increased to 10.70% on a DM basis. However, a second washing step resulted in serious losses of MFGM material.
源自富含极性脂质和膜特异性蛋白的乳脂肪球膜（MFGM）的片段，因其功能和营养特性而受到关注。酸酪乳奶酪乳清被用作MFGM纯化的来源，因为其MFGM含量比标准凝乳酶乳清高5倍以上。由于极性脂质是MFGM的主要成分且仅存在于膜结构中，因此将极性脂质含量作为总MFGM片段含量的参数。对热钙聚集过程在其对沉淀中MFGM片段的回收率方面进行了评估。该方法最初用于乳清澄清和脱脂，是钙添加、pH升高和热处理的组合。通过响应面Box-Behnken正交设计研究了pH（6.5至8）、温度（40至70摄氏度）和钙浓度（0.1至0.24 g/100 g）对沉淀质量和干物质（DM）含量以及蛋白质和极性脂质回收率（从而间接对MFGM片段）的影响。将简化二次模型拟合到实验数据中，发现具有高度显著性。未观察到异常值。发现MFGM片段的回收率高度依赖于pH，而对温度和钙添加的依赖性较小。除了MFGM蛋白外，还发现乳清蛋白参与聚集体的形成。在55摄氏度、pH 7.7和0.205 g钙/L乳清的条件下发现了最佳条件。在这些条件下，91.0%的乳清极性脂质在仅占原始乳清质量7.86%的紧实沉淀中回收了，沉淀DM上的极性脂质浓度为8.34%。用水洗涤沉淀并离心是成功的，因为在一个洗涤步骤后，几乎所有的糖都被去除了，而仍可回收75.9%的乳清极性脂质。因此，洗涤后沉淀的极性脂质含量以DM计增加到10.70%。然而，第二个洗涤步骤导致MFGM材料严重损失。
