Quality-specific effects of aging on the human taste system.

Elderly persons are known to have elevated taste thresholds, with those for bitter more affected by age, for example, than those for sweet. Do analogous quality-specific effects occur at suprathreshold levels? Young (mean age = 20.3 years, SD = 2.99) and elderly (mean age = 72.5 years, SD = 4.58) subjects made magnitude estimates of sweetness, bitterness, sourness, and saltiness for the unmixed components sucrose, caffeine, citric acid, and NaCl at three concentration levels for each. They also made magnitude estimates of the separate taste qualities in two-component mixtures of sucrose with each of the other three qualities, at various levels of the two components in each mixture. Magnitude estimates of taste intensity were interweaved with magnitude estimates of the heaviness of six weights, which subjects were to judge on the same subjective intensity scale: This is the calibration feature of the method of magnitude matching, and permits the comparison of elderly and young subjects on the absolute intensity of tastes. When unmixed components were judged, elderly subjects found the characteristic tastes of caffeine and citric acid less intense than, but those of sucrose and NaCl as intense as, younger subjects did. In judging mixtures, the elderly found bitterness, but not the other three qualities, less intense than did the young subjects.