The effect of processing conditions and ingredient interactions on the physicochemical properties of whey protein isolate-stabilized emulsions
A wide variety of food products exist in the form of oil-in-water emulsions. The bulk physicochemical properties and sensory properties of these products is largely determined by the type of emulsifier used to stabilize them. In this study the major factors which influence the properties of oil-in-water emulsions stabilized by whey protein isolate (WPI) are examined. WPI is a value-added ingredient derived from the waste water produced during cheese manufacturing.
The properties of emulsions is influenced by the processing and environmental conditions they experience during production, storage and use, for example homogenization, heating, pH, and ingredient interactions. The aim of this study was to examine these factors in a systematic way. During this study it was found that WPI forms stable emulsions above 0.8 wt%, at pH values away from its isoelectric point (pH $<$ 4 or pH $>$ 6) and temperatures below its denaturation temperature (T $<$ 75$\sp\circ$C). The emulsion stability is influenced by the ionic strength, nature of surfactant (e.g. Tween 20, SDS) and polysaccharide (e.g. dextran sulfate) concentration. These changes are induced through modification of the colloidal interactions, interfacial characteristics and/or modification of the aqueous phase. Emulsion stability was monitored through creaming, rheological, light scattering, UV-visible absorption spectroscopic and ultrasonic techniques. The results were interpreted in terms of colloidal interactions, which act between the droplets.
The knowledge gained from this research project will enable food manufacturers to improve product quality, reduce manufacturing costs and enhance energy efficiency, by providing a strong scientific foundation for understanding the properties of complex food products.