Casein
Casein, group of proteins precipitated when milk is mildly acidified. Casein constitutes about 80% of the total proteins in cow's milk and about 3% of its weight. It is the chief ingredient in cheese. When dried, it is a white, amorphous powder without taste or odor. Casein dissolves slightly in water , extensively in alkalies or strong acids. Casein is used as a food supplement and as an adhesive, a constituent of water paints, and a finishing material for paper and textiles. A variety of casein, known by the modified name paracasein, is preferred for making a plastic, through the reaction of the casein with formaldehyde , that goes into the manufacture of buttons and other small objects. It is produced by adding the enzyme rennin to milk, forming a precipitate different from the material precipitated by acids.