Isolation techniques for protein take the least refined forms of the protein and develop a highly concentrated product. A concentrated protein product allows utilization of functional properties of proteins without fat, moisture, or carbohydrate contributing to or inhibiting the system. For example, through the use of isolation techniques, the starting concentration of soy flour or grit, 40-50% protein, can increase to more than 90% (Petruccelli 1995). When other substituents such as starches and fats are present in a system, water absorption generally occurs within the carbohydrate instead of the protein (Wolf 1970). As a result, isolation plays a two-fold role in concentrating the selected protein as well as eliminating unneeded or undesirable constituents in a food product.
Soy protein holds desirable, functional properties. Such properties of isolated soy protein include the formation of gels and emulsions. The protein’s hydrophilic properties make it an ideal component in confectionary and baked goods because of its water retaining properties and ability to maintain freshness. Additional uses in food stuffs include aeration, an adhesive in meat products, color control, and inhibition or promotion of fat absorption (Wolf 1970). These functional properties have allowed soy protein to become an emerging protein and usable food constituent.
Whey, an important by-product of milk, contains almost all of the milk carbohydrate and about one-fifth of milk’s protein (Smithers 1996). Isolated whey’s value, however, derives from its protein content. Its unique functional properties provide opportunities for a variety of applications. For example, whey proteins, because of their stability to acidic conditions, are an integral part of fortifying sports drinks (Smithers 1996). However, emulsification generally serves as whey’s primary function because dispersion patterns of whey in an emulsion are sensitive to changes in pH (Demetriades, 1997). Whey’s intrinsic functional properties and applications in food systems has made what was once considered a waste by-product, a very usable and valuable protein isolate. It is important to note that casein is also a useful protein that becomes isolated from the same products as whey.
Thermal stability defined is the relationship between protein denaturation and heat load applied (DeWitt 1990). Knowing how heat affects a protein’s functionality allows for selection of a protein that will be most capable of performing its desired purpose in a system. Proteins generally adjust for survivability within their normal environment (Argos 1979). Variability outside of a protein’s normal environment, as a result, is generally not well tolerated. Additionally, awareness of thermal stability demands consistency in a processing facility due to exactness required in achieving a desirable product. Thermal stability of a protein can be divided into two occurrences that eventually result in protein denaturation; aggregation...