Abstract: In this study, the relationship between milk clotting characteristics by rennet and different protein components was discussed. Addition of whey protein concentrate (WPC), κ-casein (κ-CN), β-lactoglobulin A (β-LgA) and β-lactoglobulin B (β-LgB) to skim milk could reduce the milk clotting time, increase the viscosity after coagulation and result in a more compact microstructure, while the formation of curds was inhibited by the addition of α-La, α-CN, β-CN and total CN and the microstructure of the formed curds was relatively loose. Dynamic light scattering method was applied to determine the particle size distribution of casein micelles during coagulation. The results showed that molecular radius distribution in casein solutions added with WPC, κ-CN, β-LgA and β-LgB changed quickly, indicating rapid aggregation of the protein molecules in solutions. Bidirectional electrophoresis and mass spectrometry identification of raw milk samples with significantly differential milk-clotting properties indicated that the differential protein components related to the rennet coagulation characteristics of bovine milk were mostly bioactive trace proteins affecting breast cell metabolism.

Key words: milk proteins; milk coagulation properties; microstructure; two-dimensional gel electrophoresis; differential proteins

摘要： 研究不同乳蛋白组分对牛乳酶凝乳特性的影响，在脱脂牛乳中添加乳清蛋白浓缩物（whey protein concentrate，WPC）、κ-酪蛋白（κ-casein，κ-CN）、β-乳球蛋白（β-lactoglobulin，β-LgA和β-LgB）。结果表明： 这些乳蛋白组分可以缩短牛乳的酶凝乳时间，而且增加凝乳后的样品黏度，凝乳样品微观结构更加紧密；而添 加α-乳白蛋白（α-lactalbumin，α-La）、α-酪蛋白（α-casein，α-CN）、β-酪蛋白（β-casein，β-CN）和总酪蛋白 （casein，CN）对凝乳的形成具有抑制作用，凝乳样品微观结构较疏松。采用动态光散射法测定酶凝乳过程中酪蛋 白胶束分子粒径的分布情况，结果表明，酪蛋白溶液中添加WPC、κ-CN、β-LgA和β-LgB后，分子半径分布发生变 化，蛋白分子趋于聚集。选择酶凝乳差异明显的原料乳样品进行双向电泳与质谱鉴定，结果表明，与牛乳的酶凝乳 特性相关的差异蛋白大多是影响乳腺细胞代谢的微量生物活性蛋白质。

关键词: 乳蛋白；牛乳酶凝乳特性；微观结构；双向电泳；差异蛋白