Functional Properties of Soybean Food Ingredients in Food Systems

The food system is the transformation of raw materials into healthy food products within biophysical and socio-cultural contexts which results in production, processing, distribution, preparation and consumption of food. Food systems include components of food availability, access and utilization which underpin food security (Gregory et al., 2005). The expanding world population has resulted to a greater pressure for the consumption of plant products in foods with aesthetic and organoleptic appeal; consequently resulting in a great emphasis on the need for food ingredients with multiple functional properties. The role of soybean as a traditional food item in Far East is well recognized where it is used to make tofu, tempeh and soymilk. Advances in food technology resulted in the development of a variety of edible soy products including concentrates, isolates and extruded-expanded products; the consequence of which is increased soy consumption by populations of technically developed regions of the world (Young and Scrimshaw, 1979). Soybean is crushed into oil and defatted meal. The meal is usually used as an animal feed; a smaller percentage is further processed into food ingredients including soyflour, concentrates, isolates and textured protein. These are soy protein products used as food ingredients because of their multiple functional properties. Functional properties have been defined as “those physical and chemical properties that influence the behavior of proteins in food systems during processing, storage, cooking and consumption” (Kinsella 1976). The functional behavior of proteins in food is influenced by some physicochemical properties of the proteins such as their size, shape, amino acid composition and sequence, net charge, charge distribution, hydrophobicity, hydrophilicity, type of structures, molecular flexibility/rigidity in response to external environment such as pH, temperature, salt concentration or interaction with other food constituents (Damodaran 1997). The functional properties are the intrinsic physicochemical characteristics which affect the behavior of a food ingredient in food systems during processing, manufacturing, storage and preparation. Such functional properties include water holding, oil binding, emulsification, foam capacity, gelation, whipping capacity, viscosity and others. Functional properties are important in determining the quality (nutritional, sensory, physicochemical and organoleptic properties) of the final product as well as facilitating processing such as improved machinability of cookie dough or slicing of processed meats (Kinsella, 1979). Therefore functional properties