Proteins are a series of connected 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). Proteins found in food are essential for maintaining life and health. Proteins are compounds with a function that acts in the body, such as facilitating reactions; however, proteins are also functional in food systems. Proteins are used for a variety of reasons such as: to create an emulsion, join pieces of meat together, form a skin on the surface of a product, and form a stable foam matrix. Milk proteins such as whey and casein are isolated for many different functions in food systems such as: frothing, whipping, gelling, nutrition, flavor enhancement and emulsification (Punidadas et Rizvi 1998). Casein in milk compromises about 78% of the proteins in milk, and determining the amount of casein in milk is essential for cheese making (Punidadas and Rizvi 1998). Whey proteins found in milk are often isolated from cheese production and are used for a variety of reasons, including 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 many ways, including the Wijis method, chromatography, and cross-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 people. reasons. Soy may be added to meat products to increase the regulated amount of water that can be added to the product. Soy proteins are also a good nutritional source (L'hocine et al. 2006). Soy proteins have functional properties if...... 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 hydrosol 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. Food Chemistry Laboratory Manual FDSC 5305. Lubbock, TX: Texas Tech University, Department of Animal and Food Sciences. Vogt G and Argos P. 1997. Thermal stability of proteins: hydrogen bonds of the internal packaging? Distance-Based Approaches to Protein Structure Determination Supplement III 2: 40-46.