Psychophysical and psychohedonic functions of four common food flavours in elderly subjects

This study was designed to determine the cause of potential differences in optimal preferred flavour concentrations in four common food items between young and elderly subjects. The main objective was to investigate whether the differences in concentration-pleasantness functions could be attributed to differences in concentration-intensity (psychophysical) functions, or to differences in intensity-pleasantness (psychohedonic) functions. Groups of elderly subjects (n = 31) and young subjects (n = 25) judged four series of food items (bouillon, tomato soup, chocolate custard and orange lemonade), each with five geometrically spaced flavour concentration levels. In addition, all participants judged a series of grey surfaces as a reference series. Stimuli were judged on a 10-point scale with respect to perceived intensity and pleasantness. The results showed that the responses to the various stimuli in the series of grey surfaces were almost equivalent for young and elderly subjects. The older subjects had higher optimal flavour concentrations than young subjects for each of the four food items. The differences could be attributed to differences in both psychophysical and psychohedonic functions for all four flavours. However, changes in psychohedonic functions were less pronounced for the savoury flavours than for the sweet flavours. The higher optimal preferred flavour concentration level for the elderly could be partly explained by the phenomenon that the elderly need higher concentration levels than young subjects in order to obtain a similar perceived intensity level.