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PubMed2004

Relationship between intensity, concentration, and temperature for drinking water odorants.

Odor analyses experiments indicated that, for the concentrations and temperatures tested, odor intensity was a function of both aqueous concentration and water temperature for water containing 1-butanol, free available chlorine, geosmin, n-hexanal, 2-methylisoborneol, and trans-2, cis-6 nonadienal. At weak odorant concentrations (approximately 4 on the flavor profile rating scale) the perceived odor intensity of these six chemicals was greater when the temperature was 45 degrees C than was 25 degrees C. Both of these temperatures are commonly encountered by consumers when they use tap water. Odor response to water containing isobutanal was affected by concentration but not water temperature. Experiments also revealed that reduction in aqueous concentration did not consistently reduce odor intensity; for some aqueous concentrations and chemicals an increase in odor intensity occurred at lower concentrations.

Adult↗
PubMed1985

Accession of sweet stimuli to receptors. I. Absolute dominance of one molecular species in binary mixtures.

Intensity/time studies of sweetness response in pure solutions of each of nine different sweet stimuli have been carried out. Both variables exhibit simple power functions of the form Intensity (S) = kscns and Persistence (P) = kpcnp. In binary mixtures of these nine stimuli a depression (or negative synergism) of both sweetness intensity and persistence is observed which is predictable from the low exponents of the power functions. Combination of both power functions allows the "effective concentration" of each stimulus in a binary mixture to be calculated from its observed intensity/time characteristics. All "effective concentrations" calculable in this way show absolute dominance of one stimulus in mixtures of two irrespective of the relative proportions of the two stimuli. It is suggested that the "effective concentrations" may reflect real concentrations of a single molecular species in the microenvironment of the receptor. Thus the accession of sweet molecules to ordered, localized concentrations at the receptor is ultimately dependent on chemical structure.

Adult↗
PubMed2001

Relationship of papillae number to bitter intensity of quinine and PROP within and between individuals.

Subjects were asked to assess the bitterness of one 6-n-propyl-2-thiouracil (PROP) and two quinine HCl (QHCl) concentrations presented via filter papers of varying sizes. The number of taste papillae stimulated by these filter papers was counted in each individual. Whole mouth sensitivity to PROP was determined in a separate session. In support of other demonstrations of spatial summation, these data indicated that perceived bitterness intensity increased as a function of area of stimulation within subjects. Between subjects, there was a significant trend for the perceived bitterness of PROP to increase with the lingual density of fungiform papillae, although this trend was highly variable and was only demonstrable among those who showed at least moderate sensitivity to PROP. On the other hand, the number of stimulated fungiform papillae failed to account for individual differences in perceived bitterness of QHCl.

Adult↗
PubMedDate not supplied

Experience-induced changes in taste identification of monosodium glutamate.

Taste sensitivity for a given subject generally has been thought to be genetically determined and not plastic. Yet experience-inducible changes in human taste and olfactory sensitivities have been reported. To test a taste induction hypothesis, we exposed 17 Americans/Europeans to monosodium glutamate (MSG) in food and then compared their ability to identify MSG taste with that of 2 control groups (18 Americans/Europeans without MSG exposure and 18 Japanese). When tested on Day 11 or 12, the Americans/Europeans exposed to MSG were able to identify MSG at significantly lower concentrations than the Americans/Europeans without MSG exposure. Moreover, Japanese subjects who had prior extensive experience with MSG in Japanese food were able to identify MSG at significantly lower concentrations than the two American/European groups. The differences in identification ability between the two American/European groups challenge the notion of taste sensitivity as stable over time and support the hypothesis of an experience-inducible component in human taste.

Adult↗
PubMed2003

Differential changes in taste perception induced by benzoic acid prickling.

Benzoic acid (Bz) is a prickling compound used to preserve foods. However, its effects on taste are unknown. This work examines Bz-taste interaction using psychophysical methods [magnitude estimation (ME) and paired comparison (PC)] to measure taste intensity in aqueous solutions of pure tastants (T) and their respective mixtures with 10 mM Bz (Mix). Prototypical tastants induced basic taste qualities (mM): sucrose [90-1440, sweetness (Sw)], citric acid [1-64, sourness (So)], NaCl [15-960, saltiness (Sa)], quinine [0.01-0.64, bitterness (Bitt)], KCl (12.5-400, Sa and Bitt). MEs were analysed using Steven's and Beidler's equations. Bz increased Sw (all concentrations) and ionic tastes (low concentrations) and Bz effects were reduced by concentration increase according with quality and tastant Bz reduced Bitt(Quinine) (high concentrations). Bz reduced taste slopes (percentage decrease): Sw 45% (P<.02), So 34% (P<.01), Sa 35% or 41% (NaCl or KCl, P<.03), Bitt 33% or 60% (quinine P<.01 or KCl P<.04). Bz reduced K(diss) (affinity(-1)) (percentage reduction): Sw 79% (P<.0002), So 40% (P<.03), Sa(NaCl) 63% (P<.005), Sa(KCl) 48% (P<.04), Bitt(KCl) 64% (P<.04). Bz reduced ME(max) (percentage reduction): Sw 31% (P<.004), Bitt(Quinine) 29% (P<.03). PCs confirmed taste increases by Bz (percentage of 'Mix(intensity)>T(intensity)' answers/total answers): Sw 79-69% (90-1440 mM sucrose), So 75% (1 mM citric acid) and 71% (2 mM citric acid), Sa 75-71% (15-120 mM NaCl). Negative concentration dependence of taste increases by Bz suggests different levels of interaction. Biophysical and neurophysiological changes are discussed in relation with Bz properties and mechanism of interaction with taste.

Adult↗
PubMed2003

Calcium taste preference and sensitivity in humans. I. Gender comparisons.

Calcium is an essential nutrient, particularly during growth and during reproduction, and the latter is probably why the avidity for calcium may be greater in females of some species. However, in humans, despite widespread belief in calcium appetite, it has not been studied experimentally. Here we compared the hedonic responses of 17 men and 24 women to test whether women show a greater avidity for calcium in line with its greater biological significance for them. We find no gender difference in the hedonic response to calcium, and no change with the menstrual cycle.

Adult↗
PubMed2003

Calcium taste preference and sensitivity in humans. II. Hemodialysis patients.

Calcium is an essential nutrient. However, in humans, despite widespread belief in a calcium appetite, it has hardly been studied experimentally. Here, we compared the avidity for calcium in 10 hemodialysis patients and 10 healthy controls to test whether disturbed calcium metabolism alters the preference for calcium. Hemodialysis patients did not differ from controls in their taste responses to CaCl(2) solution. However, they found high levels of CaCl(2) in cheese tastier. Our findings are indicative of a possible increased calcium appetite related to perturbed calcium metabolism in humans. The findings also suggest that for hemodialysis patients calcium added to foods might increase their palatability.

Analysis of Variance↗
PubMed1997

Cypha [propionic acid, 2-(4-methoxyphenol) salt] inhibits sweet taste in humans, but not in rats.

Cypha, propionic acid, 2-(4-methoxyphenol) salt, is a commercially available sweet taste inhibitor used in food products. The present study examined whether or not Cypha blocked the sweet taste response of rats. This was accomplished by measuring the consummatory response of rats to sucrose solutions during short-term taste tests. Nondeprived female rats were given 2-bottle choice tests (10 min) with different sucrose solutions. When given the choice between 10% sucrose and 10% sucrose containing Cypha at concentrations of 0.0125% to 0.10%, the rats showed no reliable preference for one or the other solution. In other tests, they reliably preferred 10% sucrose to 8%, 6%, and 4% sucrose, demonstrating the sensitivity of the behavioral test. To confirm the activity of the Cypha sample, a second experiment was conducted with human subjects. Using a visual analogue scale, the subjects rated the sweetness of various sucrose solutions (0% to 10%) and 10% sucrose solutions containing Cypha at concentrations of 0.0125% or 0.025%. Cypha reliably reduced the sweetness ratings of the sucrose solution. The 10% sucrose + 0.0125% Cypha solution was judged isosweet to 2.3-2.9% sucrose, and the 10% sucrose + 0.025% Cypha solution was rated as isosweet to a 1.2% sucrose solution. Taken together, these data confirm prior reports on the sweetness-inhibitory effect of Cypha in humans and demonstrate its ineffectiveness in rats. These findings are consistent with other reported differences between rats and humans in their response to other sweetness inhibitors, as well as to artificial sweeteners.

Adolescent↗
PubMed1997

Hemodialysis increases the preference for salt in soup.

Eighteen hemodialysis patients rated 7 concentrations of salt in soup immediately before dialysis and 24 h later. Preference ratings were higher after dialysis. Patients over 65 years old did not increase their ratings. Hypertensive patients increased their preference for salt after dialysis like normotensives, but rated lower concentrations of salt as more intense and were less able to discriminate the intensity of salt taste. The findings suggest that humans may respond to reductions in bodily sodium with a delayed increase in preference for salt.

Adult↗
PubMed1997

Bidirectional modulation of sweet and bitter taste by chlordiazepoxide and Ro 15-4513: lack of effect with GABA drugs.

Five rats were trained to respond for 10% sucrose and 10% sucrose/0.006% quinine in an operant procedure. Both solutions were concurrently available on independent, variable-interval 5-s schedules of reinforcement. Rats reliably responded for both solutions throughout the sessions and made approximately 68% of their total daily responses for the sucrose solution. When injected prior to the sessions with 4 mg/kg of chlordiazepoxide, rats selectively increased quinine responding; injections of the benzodiazepine inverse agonist Ro 15-4513 (9 mg/kg) led to decreased quinine responding. The effects of both chlordiazepoxide and Ro 15-4513 were reversed by the benzodiazepine antagonist flumazenil. Presession injections of flumazenil, muscimol, baclofen, or picrotoxin all resulted in no changes in responding, or a decrease in responding for both solutions. These results are discussed in terms of a bidirectional modulation of sweet-bitter taste preference by drugs acting on the benzodiazepine receptor. Moreover, the data from these experiments suggest that any changes in the oral consumption of alcohol following administration of benzodiazepine drugs must be examined in light of their effects on taste palatability.

Animals↗
PubMed1997

Adaptation to capsaicin within and across days.

Subjects judged the time-course of the burn caused by 100 ppm capsaicin applied to the tongue on Day 1 and Day 5. On Days 2-4, they tasted hard candy containing capsaicin. Most subjects did not show adaptation within Day 1, but either plateaued after about 16 min or rose monotonically for the entire 34 min. Intensity was less on Day 5 and levelled off or declined for most subjects. Data were fit to a mathematical model of adaptation. Adaptation across days was accounted for by changes in the gains of the three processes.

Adaptation, Physiological↗
PubMed1998

Salt taste responses of the IXth nerve in Sprague-Dawley rats: lack of sensitivity to amiloride.

To explore characteristics of the salt taste function of taste receptor cells located on the posterior tongue, we recorded electrophysiological responses from the whole glossopharyngeal nerve in Sprague-Dawley (SD) rats. For all salts, relative response magnitudes increased with increased stimulus concentrations (0.2-2.0 M) of NH4+, K+, and Na+ salts. The order of effectiveness of stimulation for Cl- salts was NH4Cl > KCl > NaCl. For sodium salts, relative response magnitudes were anion dependent. Sodium salts with small anions (NaCl, NaSCN, and NaNO3) had a much stronger stimulating effect than sodium salts with large anion groups (Na2SO4, C2H3O2Na, and C6H11O7Na). The responses of the glossopharyngeal nerve to the Na+ salts of NaCl, C2H3O2Na, and C6H11O7Na were not inhibited by the lingual application of the epithelial sodium transport blocker amiloride. This is in contrast to large amiloride sensitivity of the chorda tympani nerve. Amiloride also failed to inhibit the responses to K+ salts (KCl and KC2H3O2) and to NH4Cl. These results demonstrate that taste receptors innervated by the glossopharyngeal nerve in SD rats lack amiloride sensitivity as observed in the glossopharyngeal nerve of spontaneously hypertensive and Wistar-Kyoto rats. Furthermore, the difference between the small-anion group and the large-anion group of Na+ salts in their effectiveness to produce responses in the glossopharyngeal nerve parallels the effects noted for the anion dependence in the portion of the taste response resistant to amiloride in the chorda tympani nerve. Sodium salts with the smaller anion produced the larger responses in both glossopharyngeal and chorda tympani nerves after amiloride.

Amiloride↗
PubMed1999

Group and individual gustatory reaction times and Piéron's law.

Simple reaction times (SRT) to eight substances belonging to the four classical taste families were evaluated. The same eight subjects participated in all experiments. The functional relationship between SRT and concentration for group and for individual data were examined. Equations presented by different authors to describe RT data are discussed. The Piéron function [(SRT - t0) = betaI-alpha] best fits the gustatory data collected in the present experiments. These results, together with others taken from previous studies, show that the exponent of salt and acid taste functions is lower than 1.0 with a relatively short t0. Sweet and bitter exponents were equal t0 or higher than 1, with a larger t0. Individual performances correlated with taste families for salt and acid. However, the limited samples of some solutions sets some limits to the interpretation of RT to taste substances.

Adult↗
PubMed1999

Effect of medications on taste: example of amitriptyline HCl.

Use of medications is a major factor that contributes to taste losses in the elderly. Epidemiological studies suggest that community-dwelling elderly over the age of 65 use an average of 2.9 to 3.7 medications, and this number increases significantly for elderly living in retirement and nursing homes. The tricyclic antidepressant amitriptyline HCl is used by at least half a million people aged 65 years or more. In human studies performed here, amitriptyline HCl was found to have a bitter, unpleasant taste of its own. In addition, it blocked responses to other taste stimuli in both humans and gerbils. This blockage in humans was greater when amitriptyline HCl was applied continuously to the tongue than when it was applied intermittently. Continuous application of the drug affected all of the taste qualities to varying degrees, while intermittent application led to taste decrements only for salts. Electrophysiological studies in gerbils also revealed taste decrements after a short adaptation to amitriptyline HCl.

Adaptation, Physiological↗
PubMed1990

Why do sugars taste good?

The preference humans and animals show for sweet solutions has been the subject of hundreds of publications. Nevertheless, the evolutionary origin of sweet preference remains enigmatic because of the relatively low nutritional value of sugars and the absence of specific tastes for other, more essential, nutrients. Moderate concentrations of sugars are found in most plant foods because sugars play an important role in plant physiology. Widespread occurrence of sugars in plants is paralleled by widespread preference for sugar solutions in mammals. These observations suggest that preference for sugars evolved because they are common in plants and easy to detect rather than because of any special nutritional merits they offer. Perception of sweetness cannot be used to accurately meter the metabolizable energy or nutritive value of a food.

Animals↗