Ng-Kwai-Hang K F, Hayes J F
J Dairy Sci. 1982 Oct;65(10):1895-9. doi: 10.3168/jds.S0022-0302(82)82435-1.
A rapid procedure is described for measuring casein in milk by a combination of isoelectric precipitation and amido black dye-binding. Individual milk samples from 38 cows were subsampled, preserved with potassium dichromate at a concentration of 8 mg/ml of milk, and analyzed for fat and protein by the Milko-Scan 300 and for protein and casein by the dye-binding procedure on day 1, 4, 7, and 10 after milk collection. Fat tests were not affected by sample storage time, but protein tests showed variation depending on the interval between milk sample collection and analysis. In a separate study effects of potassium dichromate used as a preservative at 0, 2, 4, 6, 8, and 12 mg/ml of milk on chemical determinations were investigated. No changes were significant in fat and protein analyzed by the infrared method for concentrations of preservative. There were no significant differences in protein determination by the two methods for nonpreserved samples. For preserved samples, the dye-binding method for protein gave determinations higher than those by the infrared method. The difference increased linearly with increasing concentration of potassium dichromate at .07% in protein for every 2 mg of potassium dichromate per milliliter of milk.
本文描述了一种通过等电沉淀和酰胺黑染料结合法相结合来测定牛奶中酪蛋白的快速方法。从38头奶牛采集的个体牛奶样本进行了二次采样，用重铬酸钾以每毫升牛奶8毫克的浓度进行保存，并在采集牛奶后的第1天、第4天、第7天和第10天，通过Milko-Scan 300分析脂肪和蛋白质，通过染料结合法分析蛋白质和酪蛋白。脂肪检测不受样本储存时间的影响，但蛋白质检测结果因牛奶样本采集和分析之间的间隔时间而有所变化。在另一项研究中，研究了重铬酸钾作为防腐剂，以每毫升牛奶0、2、4、6、8和12毫克的浓度对化学测定的影响。通过红外法分析的脂肪和蛋白质，对于不同浓度的防腐剂，其结果没有显著变化。对于未保存的样本，两种方法测定蛋白质的结果没有显著差异。对于保存的样本，蛋白质的染料结合法测定结果高于红外法。每毫升牛奶中每增加2毫克重铬酸钾，蛋白质中重铬酸钾浓度为0.07%时，差异呈线性增加。
