On the discrimination of missing ingredients: aging and salt flavor.

This study reports on the ability of young, middle-aged, and elderly persons to discriminate the presence-absence of the salt flavoring in a published recipe for a soup. Although all but one young person tested was able to make this discrimination above chance level, more than half of each of the two older groups failed to do so. Both the discrimination score and the absolute threshold for NaCl in water solution correlated significantly with age over a span from 18 to 89 yrs. These results add to previous ones from a similar study of the discrimination of an aromatic spice, marjoram (Cain et al., 1990), in demonstrating that taste and smell weakness revealed in recent psychophysical tests can reveal themselves in the perception of everyday food and beverage preparations. A secondary study compared thresholds for NaCl in water with NaCl thresholds in the presence of tomato, the principal ingredient of the published recipe. These thresholds, presumably because of "mixture suppression" of tastes, were from seven to ten times higher than thresholds in water. Although thresholds for young and old were more alike in the tomato medium than in water, the elderly nevertheless needed over twice as much salt concentration than did the young just barely to appreciate its presence. Computer evaluation of the salt content of a large number of soup recipes revealed that (a) the salt content of the tomato soup we used to study discrimination was reasonably representative of other published recipes for tomato soups and (b) that the salt content of the average of these tomato soup recipes was greater than that of the average of non-tomato soup recipes.