Proteins are a series of linked amino acids, and in food products, proteins provide both nutritional and functional properties that contribute to the quality of a food system (Christen and Smith 2000). Protein in the diet is essential for maintaining life and health. Proteins are compounds with a function that work in the body such as facilitating reactions; however, proteins are also functional in food systems. Proteins are used for a variety of reasons, for example: to create an emulsion, to bind pieces of meat together, to form a skin on the surface of a product, and to form a stable foam matrix. Milk proteins such as whey and casein are isolated for many different functions in food systems such as: foaming, whipping, gelling, nutrition, flavor enhancement, and emulsification (Punidadas and Rizvi 1998). Casein in milk compromises approximately 78% of the proteins present in milk, and determining the amount of casein in milk is essential for cheese production (Punidadas and Rizvi 1998). Whey proteins in milk are often isolated from cheese production and are used for a variety of reasons, such as as a nutritional protein supplement. Whey protein isolates are also used as a whipping agent (Punidadas and Rizvi 1998). Milk proteins can be extracted in numerous ways, such as the Wijis method, chromatography, and tangential flow filtration (Punidadas and Rizvi 1998; Christen and Smith 2000). Soy protein is commonly used in commercial food products as a relatively inexpensive form of protein for many reasons. Soy can be added to meat products to increase the regulated amount of water that can be added to the product. Soy protein is also a good source of nutrition (L'hocine and others 2006). Soy proteins have functional properties si...... middle of paper ......5: 256-259.Punidadas P and Rizvi SSH. 1998. Separation of milk proteins into casein- or whey protein-rich fractions by cross-flow filtration. International food research. 31(4): 265-272. Ryan M, McEvoy, E, Duignam S, Crowley C, Fenelon M, O'Callaghan, DM and FitzGerald RJ. 2008. Thermal stability of soy protein isolate and hydrosolate ingredients. Food chemistry. 108:503-510. Stellwagen E and Wilgus H. 1978. Relationship between protein thermostability and accessible surface area. Nature. 275: 342-343.Thompson LD and Dinh T. 2009. Acid-base chemistry. FDSC 5305 Food Chemistry Laboratory Manual. Lubbock, TX: Texas Tech University, Department of Animal and Food Sciences. Vogt G and Argos P. 1997. Thermal stability of proteins: hydrogen bonding of the internal packing? Distance-based approaches to protein structure determination III Supplement 2: 40-46.