114A-22 |
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R. CHANAMAI, R. Tyszkiewicz, W. Reeves, G. R. Horn, and R. Hammond. WILD Flavors, Inc., 1261 Pacific Ave., Erlanger, KY 41018-1260 The formation, stability and rheology of emulsions strongly depend on the composition and adsorption layer around the oil droplets. Surfactants, which are present in some food systems, may affect the adsorption layer and physical properties of emulsions. Knowledge of the properties of emulsions as affected by surfactants is therefore important for producing emulsions with desired physical characteristics. Our objective was to examine the influence of nonionic surfactants (Polyoxysorbitan monooleate, Tween 80) on the physical properties of model food emulsions stabilized with whey protein isolate (WPI), gum arabic (GA) or modified starch (MS). Sunflower oil-in-water emulsions (10 wt%) stabilized with WPI (1 wt%), GA (21 wt%) or MS (13 wt%) were prepared using a high pressure homogenizer. Tween 80 was added at different concentrations (0 to 1 wt%) before homogenization. The particle size, creaming index, surface and interfacial tensions of the emulsions were measured at 25°C. The particle size of WPI-emulsions decreased with increasing tween concentrations. However, for GA- and MS-emulsions, there was a critical tween concentration. When tween was added below the critical concentration, the particle size decreased with the tween concentration, possibly due to surfactant-polymer interactions. When tween was added above the critical concentration, the opposite trend was observed, and the emulsions became flocculated and eventually led to creaming. When the emulsions were heated at 78°C for 30 minutes in the presence of 100 mM NaCl, there was no effect on the particle size of GA or MS-emulsions (with or without tween). On the other hand, the particle size of WPI-emulsions was increased by heating, and this increase became smaller when more tween was added to the emulsions. These results are explained in term of competitive adsorption and colloidal interactions in emulsions. The physical properties of the emulsions can be controlled by addition of surfactants, which has important implications for emulsion formulation.
Session 114A, Food Chemistry: Colloidal systems and enzyme chemistry
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