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.
