It is a liquid that remains after the coagulation and straining of milk. Whey is a by-product in the production of cheese or casein and has several commercial applications. Sweet whey is obtained in the production of hard cheeses, such as cheddar or Swiss cheese. Sour whey is obtained in the production of acidic cheeses, such as cottage cheese. It is a source of whey protein, potassium, calcium and phosphorus; it prevents the development of osteoporosis.