30A-25 |
The effect of pH, CaCl2 and temperature on the stability of beverage emulsions |
R. CHANAMAI, Department of Food Science, University of Massachusetts, Amherst, MA 01003 and D. J. McClements. Beverage emulsions have a variety of different compositions and experience a variety of different processing and storage conditions. It is therefore important to understand the influence of these factors on their stability. Our objective was to examine the influence of pH, calcium ion concentration and temperature on the stability of dilute model beverage emulsions stabilized with different types of biopolymer emulsifiers: gum arabic (GA), modified starch (MS) and whey protein isolate (WPI). We also aimed to determine whether WPI could be used as a suitable alternative to polysaccharide-based emulsifiers in beverage emulsions The stability of 0.01 wt% soybean oil-in-water emulsions (d»1 µm) stabilized with GA, MS or WPI was investigated with varying pH (3 to 9), CaCl2 concentration (0 to 25 mM) and temperature (30 to 90°C). The particle size distribution and zeta-potential of emulsions were measured using a laser light scattering and a particle electrophoresis instrument, respectively. Temperature, pH and CaCl2 strongly influenced the stability of emulsions stabilized by WPI because its stabilizing mechanism was mainly electrostatic repulsion, but not those stabilized by GA or MS because their stabilizing mechanism was mainly steric repulsion. The WPI-stabilized emulsions flocculated around pH 4 to 6, particularly at higher CaCl2 concentrations and temperatures above 60°C. Calcium concentration did not influence the stability of WPI-stabilized emulsions at pH 3. These results indicated the possibility of WPI to replace GA or MS in beverage emulsions. WPI could only be used to produce stable emulsions in the absence of minerals at pH<4 or pH>6 or in the minerals fortified emulsions at pH 3. The stability of WPI-stabilized emulsions was much more sensitive to environmental conditions than GA or MS-stabilized emulsions. This study has important implications for the application of WPI as an emulsifier in beverage emulsions.
Session 30A, Food Chemistry: Lipids
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