Whey is a collective term referring to the serum or liquid part of milk that remains after the manufacture of cheese. Whey can be transformed into a dry product by different techniques. The quality of the product varies with the technology applied. Dry whey is a white to cream-colored product with a clean, neutral dairy flavor. It is manufactured by removing a substantial portion of water from fresh sweet or fresh acid whey. The whey is pasteurized and no preservatives are added. Except for moisture, all the constituents of fluid whey are retained in the same relative proportion in dry whey. In the United States, two major types of whey are available as whey protein sources: Acid whey, with a pH of <5.1, is produced from cottage cheese manufacture.
Sweet whey, with a pH of >5.6, results from rennet-coagulated cheese manufacture. Although the composition of each whey type is somewhat different and variable, both sweet and acid whey contain about 0.7% to 0.8% protein on a liquid basis, with whey proteins only representing about 10% to 12% of the total solids of whey.
Whey protein concentrate (WPC) is a white to light-cream-colored product with a clean neutral flavor. It is manufactured by drying the material resulting from the removal of sufficient nonprotein constituents from pasteurized whey so that the finished dry product contains 25% or more protein. The nonprotein constituents are removed by physical separation techniques such as precipitation, filtration or dialysis. Safe and suitable pH-adjusting ingredients may be used to adjust the acidity of WPC. Whey protein isolate (WPI) is a white to cream-colored product with a clean neutral flavor. WPI is manufactured by drying pasteurized liquid whey and removing nonprotein constituents by a variety of separation techniques that include precipitation, filtration and dialysis. The resulting dry product contains 90% or more protein. Safe and suitable pH-adjusting ingredients may be used to adjust to adjust the acidity of WPI.
The composition of whey varies considerably, depending on the milk source and the manufacturing process involved. But in general, whey is rich in lactose, minerals, vitamins and “whey proteins.” Typical Composition of Whey Protein Concentrates
Lactose, a disaccharide composed of glucose and galactose, is the only significant carbohydrate present in whey. Research suggests that lactose promotes the growth of beneficial lactic acid-producing bacteria that compete with undesirable putrefactive bacteria.
Major mineral components present in whey proteins include the monovalent sodium, potassium and chloride ions as well as the more reactive calcium, magnesium and phosphate ions. Lipids present in whey in small quantities include the glycerides typical of milkfat and the phospholipids and lipoproteins that are responsible for the fat globule membrane in milk.
Both sweet and acid whey contain about 0.7% to 0.8% protein on a liquid basis, with whey proteins only representing about 10% to 12% of the total solids of whey. Acid whey contains a higher concentration of minerals than sweet whey due to the dissolution of the colloidal calcium phosphate component of casein micelles during acidification and/or culturing of milk with lactic acid bacteria.
A complete protein is defined as a protein that contains all the essential amino acids in proportions resembling established human amino acid requirements. It is also highly digestible, so that a high proportion of the amino acids reach the body’s cells to permit their incorporation into protein.
Besides contributing to the overall amino acid profile, whey proteins supply additional nutritional benefits when used as a food ingredient. For example, alpha-lactalbumin, the second most abundant whey protein, has a high content of the amino acid tryptophan, a precursor of the vitamin niacin. Thus, because of its tryptophan content, it’s an excellent source of niacin equivalents. One niacin equivalent is defined as1 milligram of niacin or 60 milligrams of tryptophan. Niacin functions as part of a coenzyme essential for metabolism including fat synthesis, tissue respiration and utilization of carbohydrate. This vitamin promotes healthy skin, nerves and digestive tract, aids in digestion and fosters a normal appetite.
Sometimes whey proteins are used in calf milk replacers, infant formulas, nutritional beverages, formulated dairy products and comminuted meat products. In many cases, the whey solids contribute little to the functionality of the product, offering only a comparatively low-cost source of protein, carbohydrate and calcium.