Jan H.A. Kroeze

Bitterness suppression as revealed by split-tongue taste stimulation in humans ☆

QHCl-sucrose and QHCl-NaCl mixtures administered to the anterior part of the human tongue led to substantial bitterness suppression as determined by the method of magnitude estimation. In the QHCl-sucrose condition components separated by the tongues midline and those spatially mixed produced equal amounts of bitterness suppression. However, the QHCl-NaCl mixture produced significantly more bitterness suppression with the spatially mixed than with the spatially separated stimulus components. It is concluded that bitterness suppression in mixtures with sucrose occurs centrally and in mixtures with NaCl both peripherally and centrally.

Nasal, retronasal, and gustatory perception: An experimental comparison

Four odor substances (lemon aroma, rum aroma, ethyl butyrate, and amyl acetate) in different concentrations were presented nasally and orally (retronasally) in a four-alternative forced-choice procedure (detection tasks). In a further experimental condition, sucrose was added to the stimuli. Finally, the taste properties of the (nonsugared) odor stimuli were judged on seven semantic scales. In the detection of odor-containing stimuli, there were no significant differences between nasal and retronasal stimulation. In the taste conditions, however, there was a significant decline of “hits” when the stimuli contained sucrose in addition to the odor substances. Furthermore, in semantic scaling of the taste stimuli, a new variant of the taste-smell illusion was observed, namely, a tendency to attribute “suited” basic taste categories (e.g., “sweet”) to pure (nongustatory) odor stimuli.

Sense of smell disorder and health-related quality of life

OBJECTIVES To compare health-related quality of life and depression between individuals with an inability to smell (anosmia) and a comparison group of individuals with a normal sense of smell. METHODS Ninety individuals from an anosmia organization (anosmia based on self-report) were compared to 89 individuals with a normal sense of smell. The SF-36 and Beck Depression Inventory-II-NL (BDI-II-NL) were administered, along with the Questionnaire for Olfactory Dysfunction (QOD) to assess the degree of problems in daily life related to the smell impairment. RESULTS Compared to the comparison group, scores in the anosmia group differed on: the QOD-subscale Life Quality (related to tasting and smelling: p < .001) and Parosmia (Smelling odors as different: p < .001); and the SF-36 subscales of Social Functioning, Vitality, Mental Health and General Health (ps < .05). Persons with anosmia scored higher on the BDI-II-NL than persons from the comparison group (p < .01). DISCUSSION Once a smell dysfunction is recognized, interventions aiming at dealing with the loss of smell as a source of information and enjoyment, as well as at improvement of emotional wellbeing, social interaction, energy, and depression should be considered.

Effects of adaptation and cross-adaptation to common ions on sourness intensity

The effects of self and cross-adaptation of acetic acid and HCl solutions on the perception of sourness, were investigated using a filter paper method. In contrast to acetic acid and to pH-buffered acetic acid solutions, self-adaptation could not be obtained with HCl. In fact the sourness of the HCl test-stimulus after adaptation to HCl was increased compared to the sourness obtained with the unadapted tongue. Such a sourness potentiation was also observed with acetic acid and buffered acetic acid solutions after adaptation to distilled water. The results suggest that the reception process eliciting the sour taste of H+ ions and of undissociated acids are different and probably independent.

Masking and adaptation of sugar sweetness intensity

Subjects indicated the sweetness of solutions of sucrose and a mixture of sucrose and sodium chloride by means of magnitude scaling. The adapting effects of sucrose, sodium chloride and a mixture of both substances were investigated. The stimuli were delivered by a flow system to pre-defined tongue areas. Following adaptation to sucrose and to the mixture the subjective intensity of sugar sweetness decreased 54.2% and 54.6% respectively: these differences are statistically significant. Also a significant masking effect of sodium chloride was observed (87.9% reduction). No indications of cross-adaptation were found. The results were interpreted in favour of the independency of adaptation and masking.

Method of stimulation, mouth movements, concentration, and viscosity: Effects on the degree of taste adaptation

Although sensory adaptation, the gradual loss of sensation during prolonged stimulation, has been demonstrated in laboratory taste experiments, a comparable loss of taste intensity is not experienced in real-life eating situations. This discrepancy may be due to differences in the proximal stimuli or to differences in the ways the taste receptors are stimulated. In two experiments, the effects of four potentially relevant variables were investigated: stimulus intensity, stimulus viscosity, mouth movements, and presentation method. During the initial seconds of stimulation, adaptation to the weakest of the two solutions was faster. Although more viscous stimuli were less sweet, viscosity as such did not affect adaptation rate, nor did mouth movements. Among the three presentation methods, a sucrosesoaked filter paper on the tongue produced more adaptation than either sipping the solution or flowing it over the tongue. This suggests that even mouth movements far more subtle than those still present in the no-movement condition of a sip-and-spit experiment can disrupt the adaptation process.

Flavors prime processing of affectively congruent food words and non-food words

The aim of this study was to explore the use of oral flavor stimuli in an implicit measure of attitudes; the affective priming paradigm. Unpleasant (cold instant coffee) and pleasant (strawberry lemonade) chemosensory flavor stimuli were used as primes in an affective cross-modal priming paradigm. Target stimuli were food words and non-food words, that were either affectively positive or negative, thus creating affectively congruent and incongruent prime-target pairs. We observed priming for congruent flavor-word pairs, i.e. if prime and target are both positive or both negative, this led to faster evaluation of the target words than for incongruent flavor-word pairs. Furthermore, the size of the priming effect was similar for food and non-food target words, suggesting that the affective priming effect is not augmented by the use of words that are semantically related. These results provide proof of concept of indirectly measuring attitudes to flavors with the affective priming paradigm, which may provide information on attitudes in addition to explicit pleasantness ratings.

Interindividual Differences in Acuity for Odor and Aroma

To determine the olfactory acuity of 27 subjects a sensory test was presented which was divided into 4 subtests, 2 for nasal and 2 for oral stimulation. Each subtest contained 28 (4 substances × 7 concentrations) olfactory detection tasks (items). The substances used were lemon and rum aroma as well as ethyl butyrate and amyl acetate, the solvents tap water and sugared tap water. Analysis showed that the test provided a clear differentiation between subjects of low, medium, and high olfactory acuity. The intercorrelations among the test substances and the split-half reliabilities of the subtests proved relatively high, whereas only moderate to low intercorrelations among the subtests were found. This was considered an effect of intraindividual variations of olfactory sensitivity. Finally, some conclusions for the construction of acuity tests for odor and aroma are presented.

The influence of relative frequencies of pure and mixed stimuli on mixture suppression in taste

In experiments on saltiness suppression in NaCL-sucrose mixtures, the amount of suppression depends not only on the suppressing sucrose component in the mixture, but also on the relative frequencies of pure NaCL stimuli and mixed stimuli in the series. The observed variation of mixture suppression as a function of these frequencies can be explained by Helson’s adaptation level theory.

Functional equivalence of the two sides of the human tongue.

Taste sensitivity to sucrose and NaCl of the left and right side of the human tongue was compared. The results did not show a significant difference when the data of the whole experimental group were taken together. Analysis of the individual results showed that there was one exception: A female subject showed a quality-specific difference between left and right. A speculative explanation is offered for this result.