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PubMed1997

The hydrostatic and hydrodynamic volumes of polyols in aqueous solutions and their sweet taste.

The tastes and solution properties of sugar alcohols were studied in an attempt to illuminate the mechanism of sweet taste chemoreception. The SMURF method was used to measure tastetime-intensity of aqueous solutions of sugar alcohols and the results were interpreted using the Stevens power function and kinetic parameters. The apparent molar volumes, apparent specific volumes, partial molar volumes, partial specific volumes and intrinsic viscosities of the solutions were studied. Apparent molar volume reflects the size of the molecule in a hydrostatic state whereas intrinsic viscosity gives a measure of the size of the molecules in a hydrodynamic state. Generally the apparent molar volumes of the polyols are 6-13% greater than those of the parent sugars, indicating less interaction with the water structure. Apparent specific volume values can predict taste quality, and the average apparent specific volume for the sugar alcohols studied fits within the central part of the sweet range, i.e. 0.5-0.68 cm3/g, which accords with their ability to elicit a pure sweet taste response. Intensities and persistences of sweetness in the polyols followed the same trend as intrinsic viscosities.

Adult↗
PubMed1997

Distribution of non-tasters for phenylthiocarbamide and high sensitivity to quinine hydrochloride of the non-tasters in Japanese.

The percentage of non-tasters for phenylthiocarbamide in 915 Japanese students was 9.4%. The thresholds of the edge and back of the tongue to quinine hydrochloride were significantly smaller in the non-tasters than in the tasters. The thresholds of any tongue portions to NaCl, acetic acid or sucrose did not differ between the tasters and the non-tasters.

Adult↗
PubMed1998

Ad libitum mixing in a taste memory task: methodological issues.

Ad libitum mixing, an application of the method of adjustment in food research, was investigated and evaluated for the purpose of taste memory research. The difference between ascending and descending runs in mixing was studied using a wide range of prefill concentrations lower and higher than standard. The effect of training was studied by comparing subjects with two or 10 replications in the first session where a standard was present as a reference. Results showing higher reproduced concentrations after a 25 h time interval than those produced immediately are consistent with earlier results from within-subject designs. Thus, the difference in recall performance did not depend on the design of the study. No difference between ascending and descending runs in the mixing was observed, thus the prefill concentrations did not affect the reproduction of a given standard. There was no significant difference between produced concentrations after two and 10 replications, although a non-significant trend towards improved performance following 10 replications was observed after the 25 h time interval.

Adult↗
PubMed1998

The addition of CO2 to traditional taste solutions alters taste quality.

Previous studies of the effect of carbonation on taste perception have suggested that it may be negligible, manifesting primarily in increases in the perceived intensity of weak salt and sour stimuli. Assuming CO2 solutions in the mouth stimulate only trigeminal nerve endings, this result is not altogether surprising; however, there are neurophysiological data indicating that CO2 stimulates gustatory as well as trigeminal fibers. In that case, carbonation might alter the quality profile of a stimulus without producing substantial changes in overall taste intensity--much as occurs when qualitatively different taste stimuli are mixed. To address this possibility, subjects were asked to rate the total taste intensity of moderate concentrations of stimuli representing each of the basic tastes and their binary combinations, with an without added carbonation. They then subdivided total taste intensity into the proportions of sweetness, saltiness, sourness, bitterness and 'other taste qualities' they perceived. The addition of carbonation produced only small increases in ratings of total taste intensity. However, rather dramatic alterations in the quality profiles of stimuli were observed, particularly for sweet and salty tastes. The nature of the interaction is consistent with a direct effect of carbonation/CO2 on the gustatory system, although the possibility that at least some of the observed effects reflect trigeminal-gustatory interactions cannot be ruled out.

Adult↗
PubMed1999

The perceived intensity of caffeine aftertaste: tasters versus nontasters.

The length and intensity of the aftertaste of caffeine was measured in groups of tasters and nontasters in order to determine if any differential information could be provided by aftertaste perception. Results indicate that a period of 4 min is sufficient to see differences between tasters and nontasters, and that nontasters' aftertaste of the saturated solution is equal in intensity with tasters perception immediately after stimulus presentation, but then after approximately 1 min fade faster. Nontaster ratings for the weaker solution were lower throughout the entire time period.

Caffeine↗
PubMed1999

Some taste molecules and their solution properties.

The solution properties of a variety of different sapid substances from all four basic taste modalities, namely, sweet (n = 24), salty (n = 7), sour (n = 11) and bitter (n = 2), have been investigated. Some multisapophoric molecules, i.e. molecules exhibiting more than one taste, have also been included in the study in an attempt to define their properties in relation to the tastes they exhibit; eight sweet-bitter and three salty-bitter molecules were used. The density and sound velocity of their solutions in water have been measured and their apparent volumes, apparent compressibilities and compressibility hydration numbers calculated and compared. Apparent molar volumes (phi(v)) and apparent specific volumes (ASV) reflect the state of hydration of the molecules, and thus their extent of interaction with water structure. The range of ASVs reported are 0.13-0.49 cm3/g for salty molecules, 0.55-0.68 cm3/g for sweet molecules, 0.53-0.88 cm3/g for sweet-bitter molecules and a much wider range (0.16-0.85 cm3/g) for sour molecules. Isentropic apparent specific compressibilities range from -2.33 x 10(-5) to -8.06 x 10(-5) cm3/g x bar for salty molecules, -3.38 x 10(-7) to -2.34 x 10(-5) cm3/g x bar for sweet molecules, +6.35 x 10(-6) to -2.22 x 10(-5) cm3/g x bar for sweet-bitter molecules and +6.131 x 10(-6) to -2.99 x 10(-5) cm3/g x bar for sour molecules. Compressibility hydration numbers are also determinable from the measurements of isentropic compressibilities and these reflect the number of water molecules that are disturbed by the presence of the solutes in solution. This study also shows that it is possible to group isentropic apparent molar compressibility values by the taste quality exhibited by the molecules in the same order as for ASV.

Kinetics↗
PubMed1999

Perception of sweetness in simple and complex taste stimuli by adults and children.

Currently, there is little information on the ability of children to analyse complex chemosensory stimuli in terms of the presence and magnitude of the components. The present study investigates this question by comparing the ability of 95 adults and 8- to 9-year-olds to estimate the sweetness of several concentrations of sucrose in water and in three foods, namely, orange drink, custard and shortbread biscuits, using a magnitude estimation procedure. The results indicated that similar response functions were produced by adults and children for the sweetness of aqueous solutions of sucrose, custard and biscuits, but not for orange juice, where the functions produced by both female and male children were significantly flatter than those of the adults. Stimulus context may have influenced the ratings of children in the no-sucrose and highest sucrose concentration conditions with two of the foods. The absence of differences between the response functions of the female and male children with all types of stimuli indicated that gender had no influence on their responses. It is concluded that, at mid-childhood, humans are capable of estimating the sweetness of sucrose in foods, but that they have a tendency to limit the range of numbers used in their estimates of sweetness at high concentrations of sucrose in some foods.

Adult↗
PubMed2000

Responses to repeated oral irritation by capsaicin, cinnamaldehyde and ethanol in PROP tasters and non-tasters.

Both increases (sensitization) and decreases (desensitization) in oral irritation have been reported in response to repeated short-term stimulation by compounds such as capsaicin, zingerone and menthol. It is unclear why one irritant would show sensitization and another desensitization, and this is further complicated by substantial inter-individual variation in response patterns. These variations may be the result of individual differences such as that represented by sensitivity to 6-n-propylthiouracil (PROP), which has been associated with variation in the overall intensity of irritation. In addition, comparisons between irritants have almost always involved inter-study comparisons, entailing different subject groups and frequently different methods. In the studies reported here, responses to three irritants-capsaicin, cinnamaldehyde and ethanol-were examined as a function of PROP taster status. A common core of subjects also received all three irritants, allowing an assessment of the extent to which different response patterns between irritants seen previously were the result of different properties of the irritants themselves. Over a series of ten stimuli presented at 1 min intervals, PROP taster status differentiated subject responses on the basis of overall intensity, but not the pattern of responses over repeated stimulation. The group response to ethanol and cinnamaldehyde was desensitization, a pattern also shown by most of the individual subjects. In contrast, the group response to capsaicin was neither clear sensitization nor desensitization, reflecting much greater individual variability in response patterns. It is suggested that the time course to a single irritant stimulus largely determines between irritant response variations, while the inter-stimulus interval (ISI) used for a given irritant will have critical values for showing predominantly sensitization or desensitization.

Acrolein↗
PubMed2001

Changes in taste intensity perception following anterior temporal lobe removal in humans.

To investigate the role of the anterior temporal lobe in taste perception, we compared taste intensity estimations made by patients who had removal from either the left or the right anterior temporal lobe for the treatment of intractable epilepsy with a group of healthy control subjects. Estimations were made for five concentrations of each of four different tastes, as well as for five cards of varying saturations of gray, which served as a control task. A cross-modal magnitude estimation procedure was employed in which subjects used distance on a measuring tape to reflect intensity estimation. Distances were then transformed into logs, and the slope and the correlation with stimulus concentration or saturation was calculated. Correlation was taken as a measure of accuracy of estimation and slope was taken as a measure of perceived intensity. As predicted, repeated measures analysis of variance (ANOVA) revealed a significant difference between the control group and both patient groups in taste intensity estimations, but not for grayness, reflecting the importance of the anterior temporal lobe in low-level gustatory but not visual perception. Additionally, repeated measures ANOVA for slopes indicated that subjects in the right temporal group rated the bitter taste as more intense than did subjects in other groups, possibly reflecting increased intensity perception of the unpleasant bitter taste.

Adolescent↗
PubMed2001

Positional cloning of the mouse saccharin preference (Sac) locus.

Differences in sweetener intake among inbred strains of mice are partially determined by allelic variation of the saccharin preference (Sac) locus. Genetic and physical mapping limited a critical genomic interval containing Sac to a 194 kb DNA fragment. Sequencing and annotation of this region identified a gene (Tas1r3) encoding the third member of the T1R family of putative taste receptors, T1R3. Introgression by serial backcrossing of the 194 kb chromosomal fragment containing the Tas1r3 allele from the high-sweetener-preferring C57BL/6ByJ strain onto the genetic background of the low-sweetener-preferring 129P3/J strain rescued its low-sweetener-preference phenotype. Polymorphisms of Tas1r3 that are likely to have functional significance were identified using analysis of genomic sequences and sweetener-preference phenotypes of genealogically distant mouse strains. Tas1r3 has two common haplotypes, consisting of six single nucleotide polymorphisms: one haplotype was found in mouse strains with elevated sweetener preference and the other in strains relatively indifferent to sweeteners. This study provides compelling evidence that Tas1r3 is equivalent to the Sac locus and that the T1R3 receptor responds to sweeteners.

Alleles↗
PubMed2002

Bitter taste of saccharin and acesulfame-K.

The relationships among suprathreshold taste responses to acesulfame-K, Na-saccharin and 6-n-propylthiouracil (PROP) were examined in two studies. In the first study, the labeled magnitude scale was used with the high anchor labeled as 'strongest imaginable oral sensation' and in the second study, it was labeled as 'strongest imaginable sensation of any kind'. Results from the two procedures were similar. Individual differences among 65 subjects were seen in bitter responses to acesulfame-K and saccharin. Bitter responses to acesulfame-K ands accharin were positively correlated, but showed no significant relationship with responses to PROP bitterness or with PROP taster groups. Saccharin and acesulfame-K may share a common mechanism for bitter taste reception and transduction, one that varies across individuals and is different from mechanisms mediating bitter responses to PROP. Changing the instructions of the labeled magnitude scale induced a context effect. Ratings of sweetness referenced to the 'strongest imaginable sensationof any kind' were lower than ratings referenced to just oral sensations.

Adult↗
PubMed2002

Enhancement of sucrose sweetness with soluble starch in humans.

The effect of soluble starch (acid-modified starch) on taste intensity was investigated in human subjects. Different concentrations of sucrose (Suc), six sweeteners, NaCl, quinine-HCl (QHCl) and citric acid (Cit) were dissolved in either distilled water (DW; standard) or starch solution (test solution). The solutions were presented to naive subjects and each subject was requested to taste and compare the sweetness intensity between the standard and test solutions based on a scale ranging from +3 (enhanced) to -3 (inhibited). A greater sweetness intensity occurred with Suc at different concentration (0.1-1.0 M) dissolved in soluble starch (0.125% to 4.0%) than with Suc in DW. Similarly, five other different products of soluble starch at 0.25 and 4.0% resulted in enhancement of sweetness for 0.3 and 1.0 M Suc. With the sole exception of the taste of 0.3 M Suc, sweet enhancement did not occur with 0.43 M fructose, 0.82 M glucose, 0.82 M sorbitol, 0.0037 M aspartame, 0.0042 M saccharin-Na or 0.016 M cyclamate. Neither the saltiness of NaCl (0.01-0.3 M), the bitterness of QHCl (0.00003-0.001 M) nor the sourness of Cit (0.0003-0.01 M) were affected by the soluble starch. These results suggest that the taste enhancing effects of soluble starch on Suc sweetness might depend not only on the taste transduction mechanism, but also on the molecular interaction between Suc and soluble starch.

Adult↗
PubMed2002

Cross-adaptation and bitterness inhibition of L-tryptophan, L-phenylalanine and urea: further support for shared peripheral physiology.

A previous study investigating individuals' bitterness sensitivities found a close association among three compounds: L-tryptophan (L-trp), L-phenylalanine (L-phe) and urea (Delwiche et al., 2001, Percept. Psychophys. 63, 761-776). In the present experiment, psychophysical cross-adaptation and bitterness inhibition experiments were performed on these three compounds to determine whether the bitterness could be differentially affected by either technique. If the two experimental approaches failed to differentiate L-trp, L-phe and urea's bitterness, then we may infer they share peripheral physiological mechanisms involved in bitter taste. All compounds were intensity matched in each of 13 subjects, so the judgments of adaptation or bitterness inhibition would be based on equal initial magnitudes and, therefore, directly comparable. In the first experiment, cross-adaptation of bitterness between the amino acids was high (>80%) and reciprocal. Urea and quinine-HCl (control) did not cross-adapt with the amino acids symmetrically. In a second experiment, the sodium salts, NaCl and Na gluconate, did not differentially inhibit the bitterness of L-trp, L-phe and urea, but the control compound, MgSO(4), was differentially affected. The bitter inhibition experiment supports the hypothesis that L-trp, L-phe and urea share peripheral bitter taste mechanisms, while the adaptation experiment revealed subtle differences between urea and the amino acids indicating that urea and the amino acids activate only partially overlapping bitter taste mechanisms.

Adaptation, Physiological↗
PubMed2002

A brief-access test for bitter taste in mice.

Inbred mouse strains vary in their response to bitter-tasting compounds as assessed by 48 h preference tests. These differences are generally assumed to result from altered gustatory function, although such long-term tests could easily reflect additional factors. We developed a brief-access taste test and tested the responses of two inbred strains, as well as C3. SW congenic mice, to the bitter stimulus sucrose octaacetate (SOA). Water-deprived trained mice were tested with five concentrations of SOA (0.00018-0.18 mM) and distilled water in a Davis MS- 160 apparatus. Trials were 5 s in duration and stimuli were presented randomly within blocks; each stimulus trial was preceded by a water rinse trial. Each concentration was presented twice in a session and mice were repeatedly tested across consecutive days. SOA-taster mice, including the SWR/J (SW) inbred and C3. SW congenic taster (T) mice, avoided licking SOA at concentrations >0.003 mM. In comparison, C3HeB/FeJ (C3) and C3. SW demitaster mice (D) licked all concentrations at the same rate as water. Concentration-response functions were similar across strains for both the brief-access test and a parallel 48 h preference test run on separate groups of mice. Furthermore, concentration-response functions were similar whether or not the brief-access test was preceded by a 4 day, single concentration pretest with SOA. The brief-access test is a suitable assay for bitter taste function in mice because it minimizes possible post-ingestive influences on taste.

Animals↗
PubMed2002

Discrimination between the tastes of sucrose and monosodium glutamate in rats.

Conditioned taste aversion studies have demonstrated that rats conditioned to avoid monosodium glutamate (MSG) with amiloride added to reduce the intensity of the sodium component of MSG taste, will generalize an aversion for MSG to sucrose and vice versa. This suggests that taste transduction for sodium, sucrose and MSG may intersect at some point. Generalization of conditioned taste aversion indicates that two substances share similar taste features, but it does not reveal the extent of their differences. In this study, we tested how well rats can discriminate sucrose and MSG under a variety of conditions. Water-deprived rats were trained on a combination of water reinforcement and shock avoidance to discriminate between MSG and sucrose, both with and without amiloride, and with and without equimolar NaCl in all solutions. In the absence of amiloride, rats reliably distinguished between MSG and sucrose down to 10 mM solutions. However, they could correctly identify solutions only above 50 mM in the presence of amiloride, equimolar sodium chloride, or both. These results suggest that gustatory stimulation by MSG and sucrose interact somewhere in taste transduction, perhaps within taste receptor cells or gustatory afferent pathways.

Amiloride↗
PubMed2002

A high-throughput screening procedure for identifying mice with aberrant taste and oromotor function.

Little is known about how specific genes influence taste function in mammals. One of the most promising ways to fill this void is to screen the progeny of chemically mutagenized (or genetically altered) mice for aberrant taste phenotypes and then identify the mutated gene(s) that is associated with each taste anomaly. To exploit this approach, a high-throughput and robust screening procedure is needed. We have attempted to meet this demand by developing an automated procedure that assesses taste responsiveness of individual mice to palatable and unpalatable taste stimuli. We focused on three taste stimuli (quinine hydrochloride, QHCl; sodium chloride, NaCl; and sucrose) and one mouse strain (C57BL/6). We used a commercially available gustometer system that both monitors the licking responses of mice and controls the presentation of each taste stimulus during successive 5 s trials. We describe a screening procedure that (after 2 days of simple training) can generate a concentration-response curve for NaCl or sucrose during a single 30 min test session, and for QHCl over three 30 min test sessions. A normative database based on the responses of 98 mice subjected to our screening procedure is also presented. We envision that investigators could use this normative database to assess taste function in the progeny of mutagenized (or genetically altered) mice. Any mouse that deviates significantly-e.g. three standard deviations (SD)-from the mean of the normative database would be flagged as having a potentially interesting mutation. We also developed an additional second screen for identifying mice with oromotor abnormalities. This latter screen is necessary because oromotor problems could lead to false positives or negatives in the screen for taste function, but is also useful for researchers interested in genes influencing oromotor circuitry. Throughout the development of the screening protocol, we sought to balance two conflicting demands: the need to maximize the screen's sensitivity and minimize its duration. This screen represents a significant improvement over the common two-bottle preference test because it assesses taste function more specifically and in a fraction of the time.

Animals↗
PubMed2002

Temporal perception of sweetness by adults and children using computerized time-intensity measures.

There is a general paucity of knowledge of the cognitive and perceptual abilities of children to successfully undertake chemosensory-related tasks. An example is that there are no reports of temporal perception by children in time-intensity tasks, or how their responses in these tasks compare with those of adults. The latter paradigm has the potential to reveal differences that may occur during a normal eating or drinking episode that cannot be detected with single response measures. To address this shortcoming, the present study uses a computerized time-intensity method to compare the responses of adults and 8- to 9-year-olds in several measures of sweetness with three different types of stimuli. The results show that the children gave higher estimates than adults of the maximum sweetness of sucrose in water, orange drink and custard and recorded shorter sweetness durations with orange drink and custard. Both age groups, however, responded similarly to changes in concentration and the volume of stimuli with all three sensory measures. Overall, the consistency of the data from the children and the variability, which was similar to that of the adults, indicate that the tasks involved in the time-intensity paradigm were within the cognitive ability of the children. Nevertheless, further studies are needed to determine the basis of the differences found.

Adult↗
PubMed2002

Taste enhancements between various amino acids and IMP.

It is well known that a strong synergistic interaction of umami occurs between L-alpha-amino acids with an acidic side chain, such as L-Glu or L-Asp, and 5'-mononucleotides, such as inosine 5'-monophosphate (IMP). We tested taste interactions between various L-alpha-amino acids and IMP by the psychophysical method and found that taste enhancement occurred when IMP was added to several sweet amino acids, such as L-Ala, L-Ser and Gly. The enhanced quality of taste was recognized as umami, and was not blocked by the sweetness inhibitor +/-2-(p-methoxyphenoxy)propanoic acid. The total taste intensities of various concentrations of the amino acid and IMP mixtures were measured using magnitude estimation. The results showed that the potentiation ratios were larger than 1 in the cases of L-Ala, L-Ser and Gly. However, the ratio was approximately 1 in the case of D-Ala, which had an enhanced taste of sweetness. Thus the umami taste enhancement of several sweet L-alpha-amino acids by IMP was synergistic rather than additive as that of acidic amino acids.

Adult↗