Morin P, Pouliot Y, Britten M
Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Boulevard West, St-Hyacinthe, Quebec, J2S 8E3 Canada.
J Dairy Sci. 2008 Mar;91(3):871-82. doi: 10.3168/jds.2007-0658.
Although many studies have reported negative effects on cheese properties resulting from the use of buttermilk in cheese milk, the cause of these effects has not been determined. In this study, buttermilk was manufactured from raw cream and pasteurized cream, as well as from a cream derived from pasteurized whole milk. Skim milks with the same heat treatments were also manufactured to be used as controls. Compositional analysis of the buttermilks revealed a pH 4.6-insoluble protein content approximately 10% lower than that of the skim milk counterparts. Milk fat globule membrane (MFGM) proteins remained soluble at pH 4.6 in raw cream buttermilk; however, when heat was applied to cream or whole milk before butter making, MFGM proteins precipitated with the caseins. Rennet gel characterization showed that MFGM material in the buttermilks decreased the firmness and increased the set-to-cut time of rennet gels, but this effect was amplified when pasteurized cream buttermilk was added to cheese milk. The microstructure of gels was studied, and it was observed that gel appearance was very different when pasteurized cream buttermilk was used, as opposed to raw cream buttermilk. Model cheeses manufactured with buttermilks tended to have a higher moisture content than cheeses made with skim milks, explaining the higher yields obtained with buttermilk. Superior retention of MFGM particles was observed in model cheeses made from pasteurized cream buttermilk compared with raw cream buttermilk. The results from this study show that pasteurization of cream and of whole milk modifies the surface of MFGM particles, and this may explain why buttermilk has poor coagulation properties and therefore yields rennet gels with texture defects.
尽管许多研究报告称，在奶酪生产中使用酪乳会对奶酪特性产生负面影响，但这些影响的原因尚未确定。在本研究中，酪乳由生奶油、巴氏杀菌奶油以及巴氏杀菌全脂牛奶制成的奶油生产。还制备了经过相同热处理的脱脂乳作为对照。对酪乳的成分分析表明，其pH 4.6不溶性蛋白质含量比相应的脱脂乳低约10%。乳脂肪球膜（MFGM）蛋白在生奶油酪乳中于pH 4.6时仍可溶；然而，在制作黄油前对奶油或全脂牛奶进行加热时，MFGM蛋白会与酪蛋白一起沉淀。凝乳酶凝胶特性表明，酪乳中的MFGM物质会降低凝乳酶凝胶的硬度并延长凝固至切割的时间，但当将巴氏杀菌奶油酪乳添加到奶酪生产用牛奶中时，这种影响会放大。研究了凝胶的微观结构，观察到使用巴氏杀菌奶油酪乳时凝胶外观与使用生奶油酪乳时非常不同。用酪乳制作的模拟奶酪往往比用脱脂乳制作的奶酪水分含量更高，这解释了使用酪乳可获得更高产量的原因。与生奶油酪乳相比，在由巴氏杀菌奶油酪乳制成的模拟奶酪中观察到MFGM颗粒的保留效果更好。本研究结果表明，奶油和全脂牛奶的巴氏杀菌会改变MFGM颗粒的表面，这可能解释了为什么酪乳的凝固性能较差，因此会产生质地有缺陷的凝乳酶凝胶。
