Kinetic And Oxidative Stability Of Oil-In-Water Emulsions Prepared With Denatured Soy Whey Protiens And Soy Soluble Polysaccharides

With increasing consumer awareness and growing demand for healthier processed food options, there is an ever-present push for the incorporation of nourishing ingredients into foods. Many health-promoting ingredients, for example Omega-3 fats, are prone to rancidity and are insoluble in water. A current challenge facing the Ontario agri-food sector is the addition of such ingredients that can normally be added to fatty foods, but not into water-based foods such as many store-bought beverages. Furthermore, oils such as flaxseed oil are also very sensitive to oxidation when in the presence of light, heat or air, resulting in the formation of undesirable odours and flavours as well as loss in nutritional properties. The use of food emulsions is considered an attractive approach to preserve their healthfulness while minimizing rancidity. The overall goal of the present thesis was to incorporate soybean or flaxseed oil as micron-sized droplets within water-continuous emulsions using biopolymers derived from soy industrial processing waste to help ‘protect’ the oil from visual phase separation and coalescence as well as oxidative rancidity. To meet the goal, an extraction protocol to purify and concentrate the soy whey proteins (SWP) was initially developed. This was followed by establishing a method to increase the surface activity of the SWP via denaturation (dSWP). Subsequently, emulsions consisting of soybean oil or flaxseed oil prepared with dSWP and commercially-available soy soluble polysaccharides (SSPS) were analyzed for their kinetic and oxidative stability. Results clearly showed that the combination of dSWP and SSPS could: i) kinetically stabilize model oil-in-water emulsions against coalescence and phase separation more so than dSWP or SSPS alone and ii) effectively protect emulsions containing flaxseed oil from oxidative rancidity to a greater extent than a commonly-used emulsifier (polysorbate 20). Overall, this thesis yielded a novel method to emulsify and protect polyunsaturated oils using soy-based proteins and polysaccharides. The outcomes of this study offer the attractive potential of using soy-based ingredients from industrial waste in value-added food products such as beverage-type emulsions. Findings from this study may be applied to non-food products where there is a need for the development and stabilization of emulsions (e.g., pharmaceutical, cosmetics).