酪蛋白的商业等级通常由原产国和用于从牛奶中沉淀酪蛋白的酸的类型来指定。蛋白质含量的成分和纯度在一定程度上取决于牛奶的成分，在更大程度上取决于每个国家特有的生产程序。使用的酸是乳酸、盐酸或硫酸。乳酸可以作为化学物质添加，也可以通过自然发酵或培养发酵从牛奶中的乳糖中生成。现代实践中的改进已将以前归因于所用特定酸的差异降至最低。

Commercial grades of casein are usually designated by the country of origin and by the type of acid used to precipitate the casein from milk. The composition and purity with respect to protein content are determined to some degree by the composition of the milk and to a larger degree by the manufacturing procedures peculiar to each country. The acids used are lactic hydrochloric, or sulfuric. Lactic acid may be added as a chemical, or generated from the lactose in the milk by natural or cultured fermentation. Improvements in modern practice have minimized the differences formerly attributed to the particular acid used.