Proteins are amazing chemical polymers. They perform a myriad of functions, such as providing nutrition in the form of their constituent amino acids as well as energy. They serve as reactants and enzymes in chemical reactions. Protein contributes to the texture, viscosity and water-holding capacity of foods containing it. Proteins can be toxins, allergens, or hormones, and they serve as carriers for vital molecules such as oxygen in the blood (Coultate 1984). These polymers have evolved to play a role in very specific physiological functions and this chemical reactivity can be used for very unique applications beyond the evolutionary framework of proteins. The chemical and physical nature of a protein such as isoelectric point, solubility and size, as well as its biological attraction to other molecules, all can be exploited to separate a particular protein from the solution in which it resides. Typically, several steps are used to purify a particular protein. These include heating, acidifying, subjecting a solution to reducing conditions, and drying. More sophisticated techniques include chromatography, ultrafiltration, reverse osmosis, and high-pressure liquid chromatography (Kinsella and Whitehead 2001). The isolation of proteins from their original matrices allows their use in different food systems to improve qualities such as nutritional value, texture. and stability. For a protein to perform the latter functions, it must have certain characteristics such as solubility, gelation, ligand binding, or film formation properties. Today, non-native proteins are widely used to improve food quality. Products include ice cream, beverages, cereals, baked goods, snacks and dairy products...... middle of paper...... 1979. Functional properties of soy proteins. Journal America Oil Chemists' Society 56:242-258. Kinsella JE and Whitehead. 1989. Whey proteins: chemical, physical and functional properties. Advances in Food and Nutrition Research 33: 343-439. McMahon DJ and Brown RJ. 1984. Composition, structure and integrity of casein micelles: a review. Journal of Dairy Science 67: 499-512. Mendel F and Brandon DL. 2001. Nutritional and health benefits of soy protein. Journal of Agriculture and Food Chemistry 49(3):1069-1086.Southward CR. Casein products. New Zealand Dairy Research Institute. Thompson LD., Dinh T. 2009. Food Chemistry Laboratory Manual FDSC 4303/5305. Lubbock, Texas: Texas Tech University, Department of Animal and Food Sciences. Walstra P. 1990. On the stability of casein micelles. Journal of Dairy Science 73:1965-1979.