Whey is the liquid remaining after milk has been curdled and strained. It is a byproduct of the manufacturing of cheese or casein and has several commercial uses. Sweet whey is a byproduct resulting from the manufacture of rennet types of hard cheese, like cheddar or Swiss cheese. Acid whey (also known as sour whey) is a byproduct brought out during the making of acid types of dairy products, such as cottage cheese or strained yogurt. Whey proteins consist of α-lactalbumin, β-lactoglobulin, serum albumin, immunoglobulins, and proteose peptones.