Factors Affecting the Stability of Emulsions Stabilised by Biopolymers

Abstract

There has been an increase in consumer demand for healthy food products made from natural ingredients. This demand has been partly addressed by the substitution of natural alternatives to synthetic ingredients. One such example in this endeavour, is the study of the application of natural biopolymers as food emulsion stabilisers. When biopolymers such as proteins and polysaccharides or their complexes are applied as emulsion stabilis- ers, they exhibit different modes of action. These include acting as emulsifiers (polypep -tides), increasing the viscosity of the medium (polysaccharides), reducing coalescence by coating individual droplets as well as acting as weighting agents (polysaccharides and polypeptides). Biopolymers can be covalently complexed using chemical, enzymatic or thermal treatments. These treatments generally increase the robustness and solubility of the final complexes. Biopolymer complexes have been reported to show higher stability to varying temperatures, pH and ionic strength. When two incompatible biopolymers are mixed, either associative or segregative phase separation occurs. The former involves separation of oppositely charged polymers due to electrostatic repulsion and the latter involves separation of similarly charged or neutral biopolymers. In this chapter, the sta- bilising effect, complexation, mode of action, phase behaviour and future application of biopolymers in emulsions are discussed.