Czerwenka Christoph, Maier Irene, Pittner Fritz, Lindner Wolfgang
Institute of Analytical Chemistry, University of Vienna, Währinger Strasse 38, 1090 Wien, Austria.
J Agric Food Chem. 2006 Nov 15;54(23):8874-82. doi: 10.1021/jf061646z.
Heat treatment of milk induces a reaction between the milk proteins and lactose, resulting in lactosylated protein species. The lactosylation of the two major whey proteins alpha-lactalbumin and beta-lactoglobulin was investigated by reversed phase liquid chromatography-mass spectrometry (LC-MS). Three sample series, consisting of aqueous model solutions of each whey protein separately and in mixture and whole milk, were heated for different time periods, and the progression of the lactosylation reaction was monitored. The observed degrees of lactosylation and the reaction kinetics showed that the lactosylation of beta-lactoglobulin was not influenced by the presence of other components, whereas the lactosylation of alpha-lactalbumin was enhanced in whole milk compared to the aqueous model systems. An in-depth evaluation of the LC-MS data yielded information regarding changes of physicochemical properties of the whey proteins upon lactosylation. Whereas retention time shifts indicated changes in hydrophobicity for both alpha-lactalbumin and beta-lactoglobulin, changes in the charge state distribution denoting conformational alterations were observed only for beta-lactoglobulin. The analysis of different liquid and solid milk products showed that the lactosylation patterns of the whey proteins can be used as indicators for the extent of heat treatment.
牛奶的热处理会引发乳蛋白与乳糖之间的反应，从而产生乳糖基化蛋白质种类。通过反相液相色谱 - 质谱联用（LC-MS）对两种主要乳清蛋白α-乳白蛋白和β-乳球蛋白的乳糖基化进行了研究。三个样品系列，分别由每种乳清蛋白的水溶液模型溶液单独、混合以及全脂牛奶组成，加热不同时间段，并监测乳糖基化反应的进程。观察到的乳糖基化程度和反应动力学表明，β-乳球蛋白的乳糖基化不受其他成分的影响，而与水溶液模型体系相比，全脂牛奶中α-乳白蛋白的乳糖基化有所增强。对LC-MS数据的深入评估得出了有关乳清蛋白乳糖基化后理化性质变化的信息。虽然保留时间的变化表明α-乳白蛋白和β-乳球蛋白的疏水性都发生了变化，但仅观察到β-乳球蛋白的电荷状态分布变化表明其构象发生了改变。对不同液态和固态奶制品的分析表明，乳清蛋白的乳糖基化模式可作为热处理程度的指标。
