The liquid remaining after milk has been curdled and strained is known as whey. It is a byproduct of the manufacture of cheese or casein.
Sweet whey is a byproduct produced during the manufacture of rennet types of hard cheese, like Cheddar or Swiss cheese where as Acid whey or sour whey is a byproduct produced during the making of acid types of dairy products, such as cottage cheese or strained yogurt. Sweet whey has a pH greater than or equal to 5.6 and acid whey has a pH less than or equal to 5.1.
Whey proteins consist of alpha-lactalbumin, beta-lactoglobulin, serum albumin, immunoglobulins, and proteose-peptones. These are soluble in their native forms, independent of pH. Cow's milk consist of 20 percent whey protein and 80 percent casein protein, whereas human milk consist of 60 percent whey and 40 percent casein.
The amino acid cysteine in whey protein helps in the synthesis of glutathione in the body which is a ubiquitous cellular antioxidant.
Rennet or an edible acid is added to heated milk to make cheese. The edible acid makes the milk coagulate or curdle and separate the milk solids (curds) from the liquid whey. Whey contains everything that is soluble from milk after the pH is dropped to 4.6 during the process of coagulation. The solution contain 5 percent of lactose in water, with some minerals and lactalbumin.
The fat is removed and then processed by simple drying. The relative protein content can be increased by removing lipids and other non-protein materials. For example, after membrane filtration spray drying separates the proteins from whey. Whey can be denatured by heat. Heat-denatured whey can still cause allergies in some people.
Whey is used to produce whey cheeses such as ricotta, brunost, and whey butter and many other products for human consumption. It is also an additive in many processed foods, including breads, crackers, and commercial pastry, and in animal feed. Whey is used in number of health food products where it remains a popular supplement. Those taking whey protein can gain more kilograms of muscle mass than people taking the other supplements.
Soy protein and Pea protein are alternatives for those who choose not to consume animal protein or are lactose intolerant. Whey protein is commonly marketed as a dietary supplement and is sold as a nutritional supplement, which are especially popular in the sport of bodybuilding. Whey is the primary ingredient in most protein powders, which are used primarily by athletes and bodybuilders to obtain the necessary amounts of protein on a daily basis.
Whey protein has a high level of leucine, which is important for muscle growth and repair.
Whey protein typically comes in four major forms. This include concentrate (WPC), isolate (WPI), hydrolysate (WPH) and Native Whey.