Madsen Birgitte D, Rasmussen Morten D, Nielsen Mette O, Wiking Lars, Larsen Lotte B
Department of Animal Health and Welfare, Danish Institute of Agricultural Sciences, Blichers Allé, DK-8830 Tjele, Denmark.
J Dairy Res. 2004 Aug;71(3):263-72. doi: 10.1017/s0022029904000263.
We examined the physical and chemical changes in milk during early lactation, and how these changes were affected by leaving one quarter unmilked in either the first or second milking, with the purpose of discriminating between colostrum and normal milk. Milk samples were collected from each quarter of 17 cows during the first 5 d after calving and then after about 7 d and 14d. Samples were analysed for somatic cell count (SCC), fat, protein, casein, lactose, IgG1, colour, plasmin, pH and coagulation properties. Large variations occurred in both chemical and physical properties throughout the study period. Within six milkings, the concentration of casein decreased by 60%, IgG1 by 94%, and lactose increased by 34%. At milking number 6, rennet coagulation time was lowest and curd firmness was highest. The pH increased from 6.4 to 6.7 over the period of the experiment, and the colour changed from yellow (reddish) to white. Coagulation properties and the pH fell within the range of normal milk after five milkings. Measurement of colour and density appeared to be a potential method for detection of milk unsuitable for the dairy factory. Effects of omitting one quarter in one milking differed between milk components, but seemed to be of little importance to the physical properties.
我们研究了泌乳早期牛奶的物理和化学变化，以及在第一次或第二次挤奶时留一个乳区不挤奶对这些变化的影响，目的是区分初乳和正常牛奶。在产犊后的前5天，然后在大约7天和14天后，从17头奶牛的每个乳区采集牛奶样本。对样本进行体细胞计数（SCC）、脂肪、蛋白质、酪蛋白、乳糖、IgG1、颜色、纤溶酶、pH值和凝乳特性分析。在整个研究期间，化学和物理性质都出现了很大的变化。在六次挤奶内，酪蛋白浓度下降了60%，IgG1下降了94%，乳糖增加了34%。在第6次挤奶时，凝乳酶凝固时间最短，凝乳硬度最高。在实验期间，pH值从6.4升高到6.7，颜色从黄色（带红色）变为白色。经过五次挤奶后，凝乳特性和pH值落在正常牛奶的范围内。颜色和密度的测量似乎是检测不适用于乳制品厂的牛奶的一种潜在方法。在一次挤奶中省略一个乳区的影响在不同的牛奶成分之间有所不同，但对物理性质似乎影响不大。
