Thermal Denaturation, Aggregation and Gelation of Whey Proteins

Abstract

Whey is the soluble fraction of milk, rich in proteins, minerals and lactose, that is separated from the casein during the manufacture of rennet- coagulated cheese, rennet casein or acid casein. The whey produced from rennet-coagulated casein or cheese is referred to as sweet whey whereas that from mineral or lactic acid-coagulated casein is called acid whey. For decades, the dairy industry considered whey as a waste product, which was usually disposed of or used as animal feed. In recent years, whey has been recognised as a major source of nutritional and functional ingredients for the food industry worldwide (de Wit. 1990). A number of whey protein products are now manufactured from different whey types and they vary with respect to the concentration of protein, minerals, lipids and lactose. The manufacture of these products involves combinations of several processes such as ultrafiltration. diafiltration, reverse osmosis, ion exchange, evaporation and drying. Commercial whey protein products include various whey powders, whey protein concentrates (WPCs), whey protein isolates (WPIs) and fractionated proteins, such as $α$-lactalbumin and $β$-lactoglobulin (Mulvihill, 1992). The most important commercial whey protein products are WPC (up to about 85% protein) and WPI (approximately 95% protein). The principal whey proteins are $β$-lactoglobulin, $α$-lactalbumin, bovine serum albumin (BSA) and immunoglobulins (Ig).