Detection of Tastes in Mixture with Other Tastes: Issues of Masking and Aging

When one taste (masker) is strong enough, it can completelymask another taste (target) of different quality. How strongthe masker must be to do this depends on how strong the targetis. As the target concentration is increased, the masking concentrationmust be increased, too, but in ever-increasing proportion. Toquantify the conditions for such complete masking, the target'sdetection threshold was measured as a function of the masker'sconcentration, from zero to strong. This was done for 12 binarycombinations of sucrose, sodium chloride, citric acid and quininehydrochloride. The 12 functions generated show that some tastantsmask each other much more efficiently than others. Masking givesnew insight into the role of aging in taste: older (66–90years) subjects' thresholds, regardless of masking concentration,always measured a constant factor higher than younger (18–29years) subjects' thresholds (about two to seven times higher,depending on target tastant). Thus, with increasing level ofthe masker, the thresholds of young and elderly go up in parallel.Thresholds of tastants in water alone are false predictors ofelderly persons' ability to perceive ingredients like salt andsugar condiments in foods, where, because of masking, theirthresholds can be several times higher than in water. Age manifesteditself relatively mildly in sucrose and citric acid, moderatelyin sodium chloride, and strongly in quinine hydrochloride. Chem.Senses 21: 211–221, 1996.