Naomi Gotow

Enhancement of Sweetness Ratings of Aspartame by a Vanilla Odor Presented Either by Orthonasal or Retronasal Routes

When taste stimuli are presented with specific odor stimuli, the perceived intensity of taste is enhanced, a phenomenon called odor-induced taste enhancement. There is a possibility, however, that the odor substances might have stimulated the taste receptors in the oral cavity as well as odor receptors in the nasal cavity because the odor substances were dissolved in the taste solutions in some preceding studies. Schifferstein and Verlegh (1996) found that the odor-induced taste enhancement effect was not found when the subjects wore a nose clip to prevent the olfactory perception. Thus, it was suggested that the odor-induced taste enhancement did not result from the stimulation of receptors in the oral cavity. To confirm and extend their study, we presented the odor stimuli simultaneously with, but not dissolved in, the taste stimuli with a more advanced approach to stimulus presentation. The participants reported enhancement of sweetness ratings for aspartame when the taste stimuli were presented with a vanilla odor. This odor-induced taste enhancement was found when the gaseous odor stimuli were presented either by the retronasal route or by the orthonasal route. There was little possibility that the vanilla odor stimulated the taste receptors during the orthonasal stimulation because the odor stimuli were presented directly into the nasal cavity. Thus, we could show that the odor-induced taste enhancement is elicited by olfactory perception. These results also suggested that there is little functional difference between retronasal and orthonasal olfaction.

Construction of a measurement system for simultaneity judgment using odor and taste stimuli

BACKGROUND The modalities examined in previous simultaneity judgment (SJ) were limited to vision, audition, and touch. By contrast, olfaction and gustation have not been addressed to date in SJ. NEW METHOD In this study, we constructed a measurement system for performing SJ with three cross-modal, combinations of odor, taste, and light stimuli. Odor and taste stimulators were able to stimulate to only the receptors corresponding to the modalities of each stimulus, without inducing tactile sensation. Furthermore, in order to precisely calculate the time points at which stimulus reached receptors in each trial, we monitored the presented stimuli in real time. After we calculated the actual values of stimulus onset asynchrony (SOA) between standard and comparison stimuli on the basis of the records of real-time monitoring, we evaluated the temporal distributions of simultaneous response rates in each cross-modal combination. RESULTS When we fitted a Gaussian distribution to these temporal distributions, we observed low error rates in all cross-modal combinations, as demonstrated in SJ using visual, audio, and tactile stimuli. COMPARISON WITH EXISTING METHOD(S) SJ using chemical stimuli and SJ using physical stimuli exhibit the same degree of measurement accuracy. CONCLUSIONS We succeeded in development a high accurate measurement system for SJ using chemical stimuli. We attribute this success to the use of strict real-time monitoring of stimulus presentation.

A high-concentration NaCl solution does not stimulate the human trigeminal nerve at the tip of the tongue.

Conclusion. A 3 M NaCl solution does not stimulate the trigeminal nerve in the human tongue. Objectives. In rats, the trigeminal nerve has been reported to respond when the tongue is stimulated by a solution with an NaCl concentration of 0.4 M or greater. We have attempted to clarify whether or not relatively high concentrations of NaCl stimulate the trigeminal nerves of the human tongue. Materials and methods. We examined four patients whose bilateral chorda tympani nerves were resected during middle ear surgeries. We performed subjective tactile and taste tests. Next, we conducted objective examinations of the subjects’ tactile and gustatory functions by magnetoencephalography (MEG). Results. The subjective examination confirmed that all four subjects maintained normal tactile sensory functions in their tongues and that the gustatory sensation at their lingual apexes was totally abolished. Furthermore, the objective examination of the tactile function using MEG indicated that their brain responses to trigeminal nerve stimulations were normal. Further examination using MEG failed to produce brain responses to a 3 M NaCl solution in spite of their normally functioning trigeminal nerves. Therefore, we concluded that a 3 M NaCl solution does not stimulate the trigeminal nerve at the tip of the human tongue.

Retronasal aroma allows feature extraction from taste of a traditional Japanese confection

BackgroundCommon foods consist of several taste qualities. Consumers perceive intensity of a particular taste quality after noticing it among other taste qualities when they eat common foods. We supposed that while one is eating the facility for noticing a taste quality present in a common food will differ among taste qualities which compose the common food. We, therefore, proposed a new measurement scale for food perception named ‘noticeability’. Furthermore, we found that consumers’ food perceptions to common foods were modified by retronasal aroma. In this study, in order to examine whether retronasal aroma affects the relationship between noticeability and perceived intensity for taste, we evaluated participants for noticeability and perceived intensity of five fundamental taste qualities (sweetness, saltiness, sourness, bitterness, and umami) under open and closed nostril conditions using one of the most popular traditional Japanese confections called ‘yokan’.ResultsThe taste quality showed that the highest noticeability and perceived intensity among five fundamental taste qualities for yokan was sweetness, independent of the nostril condition. For sweetness, a significant decrease of correlation between noticeability and perceived intensity was observed in response to retronasal aroma. On the other hand, for umami, correlation between noticeability and perceived intensity significantly increased with retronasal aroma.ConclusionsAs the retronasal aroma of yokan allowed feature extraction from taste by Japanese consumers, we reconfirmed that consumers’ food perceptions were modified by the retronasal aroma of a common food.

Interaction between Olfaction and Gustation by Using Synchrony Perception Task

It seems that interaction between olfaction (smell sensation) and gustation (taste sensation) will stronger than other interactions among five senses, although no one has ever confirmed psychophysically. In this study, we utilized synchrony perception task to confirm this specificity comparing control condition, interaction between vision and olfaction and one between vision and gustation. We used NaCl as taste stimuli and flavor from bubbling chicken stock as olfactory stimuli. We used taste stimulator which was able to present pure gustation without tactile stimuli, and smell stimulator with original developed real time stimulus monitoring. We used LED for vision stimuli. Timing of both stimuli was shifted from −1000 ms to +1000ms with each other, and participants were instructed to judge synchronicity. Control conditions revealed that olfaction and gustation has almost equivalent temporal resolution to other sensations. And probability distribution between olfaction and gustation was quite different from other interactions including vision. These results shows interaction between olfaction and gustation is more specific.

Simultaneity judgment using olfactory–visual, visual–gustatory, and olfactory–gustatory combinations

Vision is a physical sense, whereas olfaction and gustation are chemical senses. Active sensing might function in vision, olfaction, and gustation, whereas passive sensing might function in vision and olfaction but not gustation. To investigate whether each sensory property affected synchrony perception, participants in this study performed simultaneity judgment (SJ) for three cross-modal combinations using visual (red LED light), olfactory (coumarin), and gustatory (NaCl solution) stimuli. We calculated the half-width at half-height (HWHH) and point of subjective simultaneity (PSS) on the basis of temporal distributions of simultaneous response rates in each combination. Although HWHH did not differ significantly among three cross-modal combinations, HWHH exhibited a higher value in cross-modal combinations involving one or two chemical stimuli than in combinations of two physical stimuli, reported in a previous study. The PSS of the olfactory–visual combination was approximately equal to the point of objective simultaneity (POS), whereas the PSS of visual–gustatory, and olfactory–gustatory combinations receded significantly from the POS. In order to generalize these results as specific to chemical senses in regard to synchrony perception, we need to determine whether the same phenomena will be reproduced when performing SJ for various cross-modal combinations using visual, olfactory, and gustatory stimuli other than red LED light, coumarin, and NaCl solution.

Trial measurement of brain activity underlying olfactory-gustatory synchrony perception using event-related potentials from five female participants

Temporal synchrony between odor and taste plays an important role in flavor perception. When we investigate temporal synchrony between odor and taste, it is necessary to pay attention not only to physical simultaneity of the presentation of olfactory and gustatory stimuli, but also to the perceptual simultaneity between the two stimuli. In this study, we examined short‐latency brain activity underlying synchrony perception for olfactory–gustatory combinations. While five female participants performed a simultaneity judgment (SJ) task using soy sauce odor and salt solution, single‐channel event‐related potentials (ERPs) were recorded at the position of Cz. In each trial, the participant was asked whether olfactory and gustatory stimuli were perceived simultaneously or successively. Based on the judgment responses acquired from participants (i.e., simultaneous or successive), ERP data were classified into two datasets. The means of ERPs from each participant were calculated for each type of judgment response, considering the onset of olfactory or gustatory stimuli (OERPs or GERPs, respectively) as the starting point. The latencies of the P1 component of GERPs were very similar between simultaneous and successive judgment responses, whereas the P1 amplitudes differed significantly. These results indicated that neural activity affecting SJ for an olfactory–gustatory combination is generated during a period of about 130 ms from the onset of gustatory stimulus. Thus, olfactory and gustatory information processing related to flavor perception (more specially, synchrony perception between odor and taste) might be initiated at a relatively early stage of the central pathway.

Multi-Sip Time–Intensity Evaluation of Retronasal Aroma after Swallowing Oolong Tea Beverage

In most cases, a meal cannot be finished with a single bite and sip. During eating and drinking, consumers receive dynamic food perceptions from sensory attributes in foods. Thus, we performed multi-sip time–intensity (TI) evaluation of sensory attribute. In each of ten trials, the participant evaluated continuously the intensity of retronasal aroma for 60 s after swallowing oolong tea. We compared the TI parameters (Imax: maximum intensity, Tmax: time point at which intensity reached the maximum value, AUC: area under the TI curve, Dplateau: duration between the first and last time points with values exceeding 90% of the maximum intensity, Rinc: rate of intensity increase between the first time points with values exceeding 5% and 90% of the maximum intensity, and Rdec: rate of intensity decrease between the last time points with values exceeding 5% and 90% of the maximum intensity) and TI curves among the ten trials, and approximated each TI curve with an exponential model. Some TI parameters (Imax, Tmax, AUC, and Rinc) differed significantly between the first and subsequent trials. The TI curve was significantly lower in the first trial than in the subsequent trials, and TI curve during the time from starting the evaluation to reaching maximum intensity was significantly lower in the second trial than in the subsequent trials. The time constant of the fitted exponential function revealed that the decay of retronasal aroma intensity was slightly faster in the second through fourth trials than in the first and the fifth through tenth trials. These results indicate that olfaction might be more perceptive while consumers sip a cup of the beverage.

Familiarity and Retronasal Aroma Alter Food Perception

IntroductionWhen participants eat foods, they direct their attention to the particular taste quality that is the target of evaluation and subsequently perceive the intensity of the attended taste quality. We defined the ease with which participants pay attention to a particular taste quality as the “noticeability” of that quality. In our previous study, Japanese participants evaluated noticeability and intensity of five fundamental taste qualities (sweetness, umami, saltiness, sourness, and bitterness) under open- and closed-nostril conditions, using a popular traditional Japanese confection, yokan. The correlation between noticeability and intensity of sweetness was significantly reduced when participants were tested with open nostrils. Therefore, we hypothesized that high familiarity with a food and its olfactory information is necessary to decrease the correlation between these two scales.MethodsIn order to verify this hypothesis, we asked Japanese and German participants, who have different food cultures, to subjectively evaluate yokan, which is familiar to Japanese but unfamiliar to Germans. In a control condition, marshmallows were used which are familiar to all participants. Participants consumed each food under open- and closed-nostril conditions and evaluated the noticeability and intensity of the five fundamental taste qualities.ResultsThere were significant differences between the participants’ groups as the correlation between noticeability and intensity was reduced significantly only for sweetness of a familiar food under open-nostril condition.ConclusionsThese results support our hypothesis that high familiarity with a food and its olfactory information might be necessary to decrease the correlation between noticeability and intensity of a particular taste quality.ImplicationsThis finding suggests that perception of a food is influenced by its familiarity and retronasal aroma. These results suggest when a food is unfamiliar, the noticeability and intensity of a particular taste quality are not much altered by the retronasal aroma, but when a food is highly familiar, retronasal aroma serves to decouple noticeability and intensity of a given taste quality.

A method for psychophysical screening of odorants for use in city gas based on olfactory adaptation tolerance

IntroductionIn many developed nations, natural gas (so-called city gas) is supplied as a utility for cooking, heating, and hot-water supply. Because natural gas is odorless, city gas must be odorized so that it can be detected in the event of a leak. Although high adaptation tolerance is an important criterion for city gas odorants, there is yet no standard method of evaluating the psychophysical suitability of new candidate odorants in terms of olfactory adaptation. In order to address this situation, we developed a method for psychophysical screening of new candidate odorants for use in city gas based on adaptation tolerance.MethodsWe used the main component of the conventional city gas odor (tertbutylmercaptan, TBM) and six new candidate odorants: cyclohexene (CH), ethyl isobutyrate (EI), isovaleric acid (IVA), 2-hexene (HEX), 1,5-cyclooctadiene (COD), and 1-methylpyrrolidine (MEP). Participants evaluated the perceived intensity of a continuously presented odor at a fixed concentration. After the time-intensity curves were quantitatively classified into fast or slow adaptation patterns, we compared the number of intensity curves classified into each pattern between TBM and each new odorant.ResultsOur results revealed that HEX has a significantly higher adaptation tolerance than TBM, and that the other five new candidate odorants were almost equivalent to TBM in terms of adaptation tolerance.ConclusionWe concluded that all of the new candidate odorants used in this study passed the psychophysical screen based on adaptation tolerance, and are therefore suitable for use in city gas.