Whey protein is a mixture of proteins isolated from whey, the liquid material created as a by-product of cheese production. The proteins consist of α-lactalbumin, β-lactoglobulin, serum albumin and immunoglobulins. Whey protein is commonly marketed as a dietary supplement, and various health claims have been attributed to it. An authoritative review published in 2010 concluded that the provided literature did not adequately support the proposed claims.
Production of whey
Whey is left over when milk is coagulated during the process of cheese production, and contains everything that is soluble from milk after the pH is dropped to 4.6 during the coagulation process. It is a 5% solution of lactose in water with lactalbumin and some lipid content. Processing can be done by simple drying, or the relative protein content can be increased by removing the lactose, lipids and other non-protein materials. For example, spray drying after membrane filtration separates the proteins from whey.
Whey can be denatured by heat. High heat (such as the sustained high temperatures above 72 °C associated with the pasteurization process) denatures whey proteins. While native whey protein does not aggregate upon renneting or acidification of milk, denaturing the whey protein triggers hydrophobic interactions with other proteins, and the formation of a protein gel.
The protein in cow's milk is 20% whey and 80% casein. The protein in human milk is 60% whey and 40% casein. The protein fraction in whey constitutes approximately 10% of the total dry solids in whey. This protein is typically a mixture of beta-lactoglobulin (~65%), alpha-lactalbumin (~25%), bovine serum albumin (~8%) (see also serum albumin), and immunoglobulins. These are soluble in their native forms, independent of pH.
Major forms and uses
Commercially produced whey protein from cow's milk typically comes in four major forms:
- Concentrates (WPC) have typically a low (but still significant) level of fat and cholesterol but, in general, compared to the other forms of whey protein, they are higher in carbohydrates in the form of lactose — they are 29%–89% protein by weight.
- Isolates (WPI) are processed to remove the fat and lactose — they are 90%+ protein by weight. Like whey protein concentrates, whey protein isolates are mild to slightly milky in taste.
- Hydrolysates (WPH) are whey proteins that are predigested and partially hydrolyzed for the purpose of easier metabolizing, but their cost is generally higher. Highly hydrolysed whey may be less allergenic than other forms of whey.
- Native whey protein is extracted from skim milk, not a byproduct of cheese production, and produced as a concentrate and isolate.
Whey protein is commonly marketed as a dietary supplement, typically sold in powdered form for mixing into beverages. The products have varying proportions of the major forms above, and are promoted with various health claims. In 2010 a panel of the European Food Safety Authority (EFSA) examined proposed health claims made for whey protein: satiety, weight loss, reduced body fat, increased muscle, increased strength, increased endurance and faster recovery after exercising. The EFSA concluded that the provided literature did not adequately support the proposed claims.