WebMD indicates that 100 percent whey protein is composed solely of a protein derived from milk. Whey is the liquid that remains after milk is turned into cheese. If the protein contained in whey is isolated from the other components, it is called whey protein. Purified whey protein is usually a dry powder.
According to Medical News Today, whey protein consists of beta-lactoglobulin, alpha-lactalbumin, bovine serum albumin and immunoglobulins. Whey protein is sold as whey protein concentrates, in which the crude whey has had some of the non-protein components removed. Whey protein concentrates can contain anywhere from 30 percent to 90 percent whey protein. Whey protein isolates are further purified to remove everything except the protein and may be 90 to 100 percent whey protein. Whey protein hydrolysate is whey protein that has been partially broken down. It is commonly used as a source of protein in medical applications because it is easy to digest and has a very low potential to cause allergic reactions.
Purified whey protein is often used as a source of dietary protein that does not contain any fat or carbohydrates. WebMD reports that consuming whey protein in combination with strength training may help increase lean body mass, muscle strength and muscle size.