Food Proteins: Protein Isolation and Thermal Stability

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Introduction

Foods are complex systems composed of different components, among which proteins play important roles in the structure, texture, and stability of many foods (Hemar and others 2001). Protein isolates and their concentrated products are commonly and widely used in the food industry for both their added functionality and their nutritive contributions. The functionality of ingredients is important in preparation, processing, storage, quality and sensory attributes of foods (Culbertson 2007). Aside from these functions, proteins also increase solubility, water-holding capacity, elasticity, gelation, emulsification and foaming (Smith 2003). Protein isolates are generally about 90-95% protein while protein concentrates are about 65 to 70% protein (Thompson and Dinh 2010). The protein concentrates or isolates are added to foodstuffs that lack the inherent properties mentioned above (solubility, gelation, emulsification and foaming). Such foodstuffs include: extruded foods, textured meat products, whipped toppings, and protein-rich drinks (Kinsella, 1994).

The use of a protein concentrate or isolate in a food source is dependent on its functional properties which are influenced by the biochemical nature of the protein and the method of extraction and purification used for its derivation. The structure of the protein is of extreme importance in its ability to function in food system. The amino acid sequence of a protein determines the protein folding and three dimensional (3D) appearances. Additionally, the quaternary structure, defined by the number of subunits and the formation of oligometric unit, along with the 3D structure is very important to the overall functionality of a protein concentrate or isolates (...

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