Noëlle Beno

Just Noticeable Differences in Component Concentrations Modify the Odor Quality of a Blending Mixture

The odors we perceive are mainly the result of mixtures of odorants that, however, are commonly perceived as single undivided entities; nevertheless, the processes involved remain poorly explored. It has been recently reported that perceptual blending based on configural olfactory processing can cause odorant mixtures to give rise to an emergent odor not present in the components. The present study examined whether specific component proportions are required to elicit an emergent odor. Starting from the composition of a ternary target mixture in which an emergent pineapple odor was perceived, 4 concentration levels of each component were chosen to elicit just noticeable differences (JNDs). Each combination of levels was used to design sample mixtures. Fifteen subjects evaluated the intensity, typicality, and pleasantness of each sample mixture against the target mixture in a paired-comparison protocol. Statistical modeling showed that a variation of less than 1 JND in one of the components was sufficient to induce a significant decrease in pineapple odor typicality in the ternary mixture. This finding confirms previous findings on perceptual blending in simple odorant mixtures and underscores the human ability to discriminate between odor percepts induced by mixtures including very similar odorant proportions.

Synergy and Masking in Odor Mixtures: An Electrophysiological Study of Orthonasal vs. Retronasal Perception

Perceptual interactions in a model of wine woody-fruity binary mixtures were previously reported in a psychophysical study performed through orthonasal stimulation only. However, recent studies suggested that the perception of food-like and nonfood-like odors may depend on the route of stimulation. The aim of the present study was two-fold: first to examine the neural correlates of perceptual interactions using electroencephalogram (EEG)-derived event-related potentials (ERPs) and second to test the influence of the stimulation route on quality perception. Therefore, we designed an experiment with 30 subjects to study perceptual interactions in woody-fruity mixtures and compared ortho- vs. retronasal stimulation sites on perceived odor quality and ERPs. The results revealed synergy or masking of the fruity component, depending on the woody component level. Synergy was supported by larger N1 amplitude of the ERP. Furthermore, mixtures including a medium level of the woody odor elicited a strong increase of P2 amplitude only retronasally. This study evidenced for the first time electrophysiological correlates of both perceptual synergy and masking on the early component of the ERPs and confirmed that retro- vs. orthonasal stimulation route induces different neural processes that are reflected in the late component of the ERP.

Tap water consumers differ from non-consumers in chlorine flavor acceptability but not sensitivity.

Unpleasant taste and especially chlorine flavor is one of the most common reasons advocated for choosing tap water alternatives as drinking water. As a consequence, the putative link between sensitivity to chlorine flavor and tap water consumption is an issue in drinking water habits studies. In the present study, we set out to examine such a link following a strategy in which we measured chlorine flavor perception at threshold and supra-threshold level for two groups of participants selected on their drinking water consumption habits. The first group included exclusive tap water consumers and the second group included exclusive bottled water consumers. In a first experiment, we used the constant stimuli procedure to evaluate the chlorine flavor detection threshold of a group of 20 tap water consumers and a group of 20 non-consumers. In a second experiment, a group of 18 tap water consumers and a group of 17 non-consumers evaluated supra-threshold flavor intensity, liking and acceptability for eight chlorinated solutions (0-10mg/L Cl(2)). The results revealed no significant difference in chlorine flavor detection threshold and supra-threshold sensitivity between tap water consumers and non-consumers. Nevertheless, tap water consumers showed a higher liking score for chlorinated solutions and were found to be more inclined to accept these solutions as drinking water. Taken together these findings suggested that consumers may disparage chlorine flavor in drinking water on the basis of their tap water cognitive representation.

Perceptual Interactions in Complex Odor Mixtures: The Blending Effect

The perception of everyday odors relies on elemental or configural processing of complex mixtures of odorants. Theoretically, the configural processing of a mixture could lead to the perception of a single specific odor for the mixture; however, such a type of perception has hardly been proven in human studies. Here, we report the results of a sorting task demonstrating that a six-component mixture carries an odor clearly distinct from the odors of its components. These results suggest a blending effect of individual components’ odors in mixtures containing more than three odorants.