Thickeners may function in four different ways: (J) by stabilizing an emulsion with a high volume percentage of internal phase, (2) by increasing the viscosity of the external phase, (3) by forming an elastic network in the external phase, and (4) by removing a portion of the external phase. An example of the first kind is mayonnaise, where egg yolk lipoprotein stabilizes an oil-in-water emulsion in which the internal phase (oil) represents more than 70% of the total volume. As the particle size of the oil droplets decreases, the relative amount of water that is immobilized around the surface increases, and the amount of mobile external phase (free water, in a nonthermodynamic sense) decreases, contributing to the high viscosity and body of the final product.

Certain gums form aqueous solutions that have a high viscosity (Table 1). When such a solution is used as the water component of a food formula, the viscosity of the final product reflects the viscosity of the solution. In a simple salad dressing formulation, increased viscosity in the aqueous phase slows down the flotation rate of the oil droplets formed during shaking and (in this sense) stabilizes the emulsion. Commercial batters (ie, cake, cake donut, and fish breading) require a certain viscosity for optimum functionality; gums may be used to impart and control batter viscosity.

Table 1. Properties of Some Gums

1% solution Viscosity, mPa-s

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