牛羊乳蛋白质粒度对其热处理沉淀率的影响

研究牛羊乳蛋白质粒度大小对其热处理沉淀率的影响。采用离心沉淀、原子力显微镜、激光粒度仪和SDS-PAGE分析热处理后（95 ℃，15 min）牛羊乳蛋白质沉淀率、表面形貌、牛羊鲜乳蛋白质粒度和酪蛋白组成。结果表明：羊乳热处理后沉淀率显著高于牛乳（p＜0.05）；羊乳蛋白质粒子明显大于牛乳，其蛋白质热处理片状凝聚程度（35 858.15 nm2）大于牛乳（18 215.18 nm2）；鲜牛乳蛋白质粒度大小主要集中在1 nm以下，鲜羊乳蛋白质粒度在1 nm以下相对较少，主要分布在1～1 000 nm之间；牛羊鲜乳酪蛋白主要有β-酪蛋白和αs1-酪蛋白两种，相对分子质量分别为34 000和26 000左右。牛乳的热稳定性高于羊乳；蛋白质粒度大小是影响其热稳定性的直接因素；原子力显微镜结合激光粒度仪是分析乳蛋白粒度的有效手段。
In the paper influence of particles size on protein sedimentation rate from cow and goat after heat treatment（95 ℃，15 min）were explored. Centrifugal sedimentation，atomic force microscope，laser particle size analyzer，and SDS-PAGE methods were used to determine protein precipitation rate，and protein surface morphology after heat treatment，casein composition，and protein particle size of fresh milk respectively. The results showed that protein sedimentation rate of goat milk was significantly higher than that of cow milk（P < 0.05），protein particles size of goat milk were significantly bigger than that of cow milk，the clumping together degree（35 858.15 nm2） of goat milk protein were bigger than that （18 215.18 nm2） of cow milk，fresh cow milk protein particle size mainly focused on 1 nm or less，that of fresh goat milk protein mainly distributed during the range of 1～1 000 nm，fresh cow milk and goat milk have two kinds of casein mainly，beta casein and alpha s1-casein，and their molecular weight are 34 000 and 26 000 respectively. Thermal stability of cow milk is better than that of goat milk. Protein particle size is the direct influence factor on the thermal stability of milk protein. Atomic force microscopy combined with laser particle size analyzer is an effective way to analyze the particle size of milk protein