Wikipedia Article About Whey cheeses on Wikipedia Whey or milk plasma is the liquid remaining after milk has been curdled and strained; it is a by-product of the manufacture of cheese or casein and has several commercial uses. Whey is used to produce ricotta and gjetost cheeses and is used to make many other products for human consumption and as an animal feed. Whey proteins mainly consist of α-lactalbumin and β-lactoglobulin. Depending on the method of manufacture, it may also contain glycomacropeptides (GMP).