FIGURE 3-3 Magnitude of bitter or sweet taste of various solution mixtures. Adding sodium acetate to a mixture of sucrose and urea increases the sweet, sucrose taste while decreasing the bitter urea taste.

NOTE: M = molarity of solution.

SOURCE: Breslin and Beauchamp, 1997. Adapted by permission from Macmillan Publishers Ltd: Nature 387(6633):563, copyright 1997.

sodium acetate was added to sugar solutions without urea, indicating that it is the suppression of bitterness by sodium acetate that is responsible for the improved taste of those solutions (Breslin and Beauchamp, 1997).

Influence on water activity (the amount of unbound water) is another proposed reason that salt may potentiate flavors in foods. Use of salt decreases water activity, which can lead to an effective increase in the concentration of flavors and improve the volatility of flavor components (Delahunty and Piggott, 1995; Hutton, 2002). Higher volatility of flavor components improves the aroma of food and contributes greatly to flavor.

In short, salt plays a role in enhancing the palatability of food flavor beyond imparting a desirable salt taste. This non-salty sensory role may be magnified in products that have reduced amounts of other positive sensory properties (e.g., low-fat products) or increased amounts of non-preferred flavors (e.g., foods fortified with often bitter antioxidants). Consequently, in reducing salt in the food supply, it may often be necessary to identify ways to replace the flavor-modifying effects of salt. This illustrates the technological challenges that have to be met in successfully reducing salt in complex foods while maintaining their palatability. Further research is needed to understand all of the perceptual attributes of salt in foods.