Behavioural and physiological responses to two food odours

Abstract

Consumer food choice and intake are largely controlled by unconscious processes, which may be reflected better by implicit physiological and behavioural measures than by the more traditional explicit sensory tests. In this study, 26 human participants were exposed to an orange (pleasant) and a fish (unpleasant) odour presented in three different concentrations perceived as weak, medium and strong intensity, and five replications in a semi-random order via an olfactometer (Burghart OM2). Reactions to these odours were measured implicitly by means of facial expressions (automatically analysed with FaceReader), skin conductance responses and heart rate frequency (automatically analysed by Biolab), and explicitly with pleasantness ratings. Facial expressions reflected the odour’s valence (71% explained variance) and ranged from neutral (orange) to sadness/disgust/anger (fish) but showed additional differentiation with respect to odour intensity (15% explained variance). Skin conductance responses were largest for the unpleasant odour (p < 0.05), but showed no intensity effect. The unpleasant odour resulted in increased heart rate whereas the pleasant odour resulted in reduced heart rate (p < 0.05). The heart rate effects increased with intensity (p < 0.05). Different degrees of exposure were reflected in the implicit behavioural and physiological tests but not in the explicit pleasantness test. In summary, implicit physiological and behavioural responses provide detailed information on specific food odours that may not be provided by other more explicit tests.