Cheese is a type of dairy product produced in a range of flavors, textures, and forms by curdling of milk, usually from cows, goats or sheep, and sometimes of water buffalo. During production, milk is usually acidified and either the enzymes of rennet or bacterial enzymes with similar activity are added to cause the protein casein to coagulate. The solid curds, consisting of proteins and milkfat, are then separated from the liquid whey and pressed into finished cheese. Some cheeses have aromatic molds on the outer layer or rind, while others have them throughout.