Acidification, commercial caseinates

Commercial casein is usually manufactured from skim milk by precipitating the casein through acidification or rennet coagulation. Casein exists in milk as a calcium caseinate-calcium phosphate complex. When acid is added, the complex is dissociated, and at pH 4.6, the isoelectric point of casein, maximum precipitation occurs. Relatively little commercial casein is produced in the United States, but imports amounted to well over 150 million lb in 1981 (USDA 1981C). Casein is widely used in food products as a protein supplement. Industrial uses include paper coatings, glues, plastics and artificial fibers. Casein is typed according to the process used to precipitate it from milk, such as hydrochloric acid casein, sulfuric acid casein, lactic acid casein, coprecipitated casein, rennet casein, and low-viscosity casein. Differences... 

Following denaturation, the whey proteins coprecipitate with the caseins on acidification to pH 4.6 or addition of CaCl2 at 90°C, to yield a range of products known as casein-whey protein co-precipitates (Figure 4.43). The main attraction of such products is an increase in yield of about 15%, but the products also have interesting functional properties. However, they have not been commercially successful. 

In their collection, it is not difficult to stumble upon items made of casein, a milk protein obtained via acidification or enzymatic action. The resulting curds can be dried, molded, and treated with a hardening agent to yield commercial plastic. Casein had its heyday as a commercial plastic in the early 1900s the same time period when many other items that are found in the Kolsch s collection were produced. 

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