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PubMed1994

Type of test-meal affects palatability and eating style in humans.

Effects of palatability on the meal as a whole or the microstructure of meals are often inconsistent or even divergent. Is this attributable to the nature of the test meals? In the present study, three frequently used types of meals were offered to seven normal-weight women: conventional courses, sandwiches and semi-liquid items. Each meal was composed of four items of either high or medium-low palatability. The type of meal appeared to be the major factor determining the level of palatability and of every dependent variable. Energy intake was influenced by palatability level in conventional meals only. The microstructure of meals was responsive to palatability only in sandwich and semi-liquid meals. The data suggest that palatability effects are detectable beyond a minimum threshold. In addition, characteristics of eating style appeared to be very stable within individuals across meal types and palatability conditions.

Adult↗
PubMed1979

Sodium deprivation alters neural responses to gustatory stimuli.

The effects of sodium deprivation for 10 d, a period sufficient to induce sodium appetite, on gustatory nerve discharges in rats were determined. Chorda tympani responses to concentration series of sodium chloride, sucrose, hydrochloric acid, and quinine hydrochloride were recorded and analyzed without the experimenter knowing the animal's deprivation condition. After deprivation, both whole nerve and single nerve fiber responses to sodium chloride were smaller; NaCl-best fibers, those more responsive to sodium chloride than to sucrose, hydrochloric acid, or quinine, were most affected. Thresholds had not changed; however, slopes of the stimulus-response functions for sodium chloride were lowered. Comparable changes in responses to the other stimuli did not occur. These results were discussed with respect to a possible relationship between changes in sodium chloride responsivity and changes in sodium intake, differences between methods of inducing sodium appetite, coding of taste quality and intensity, and mechanisms which might effect the responsivity change.

Animals↗
PubMed2006

Application of a molecular sensory science approach to alkalized cocoa (Theobroma cacao): structure determination and sensory activity of nonenzymatically C-glycosylated flavan-3-ols.

Application of comparative taste dilution analyses on nonalkalized and alkalized cocoa powder revealed the detection of a velvety, smoothly astringent tasting fraction, which was predominantly present in the alkalized sample. LC-MS/MS analysis, 1D- and 2D-NMR, and CD spectroscopy as well as model alkalization reactions led to the unequivocal identification of the velvety, smoothly astringent molecules as a series of catechin- and epicatechin-C-glycopyranosides. Besides the previously reported (-)-epicatechin-8-C-beta-D-galactopyranoside, additional flavan-3-ol-C-glycosides, namely, (-)-epicatechin-8-C-beta-D-glucopyranoside, (-)-catechin-8-C-beta-D-glucopyranoside, (-)-catechin-6-C-beta-D-glucopyranoside, (-)-epicatechin-6-C-beta-D-glucopyranoside, (-)-catechin-8-C-beta-D-galactopyranoside, (-)-catechin-6-C-beta-D-galactopyranoside, (-)-catechin-6-C,8-C-beta-D-diglucopyranoside, (-)-epicatechin-6-C,8-C-beta-D-digalactopyranoside, (-)-catechin-6-C,8-C-beta-D-digalactopyranoside, and epicatechin-6-C,8-C-beta-D-diglucopyranoside, were identified for the first time in cocoa. Most surprisingly, these phenol glycoconjugates were demonstrated by model experiments to be formed via a novel nonenzymatic C-glycosylation of flavan-3-ols. Using the recently developed half-tongue test, human recognition thresholds for the astringent and mouth-drying oral sensation were determined to be between 1.1 and 99.5 micro mol/L (water) depending on the sugar and the intramolecular binding position as well as the aglycone.

Adult↗
PubMed2001

[Taste impairment in Alzheimer's disease].

We conducted a study of Alzheimer's disease focusing on taste impairment to determine at which step of gustatory information processing (discriminative or perceptive, gnosic or associative, gustatory-verbal) possible perturbations might be located. We used various foods found in a normal diet. Twenty patients and a matched control group participated in this study. The patients were divided into two subgroups according to disease severity (mild, moderate or severe). The study showed that patients with Alzheimer's disease exhibited an impairment at all three levels of gustatory information processing. Impairment of discriminative and gustatory-verbal stages was more obvious in the group of patients with severe Alzheimer's disease. Our study also showed that the gustatory deficiency can be described as an associative agnosia in the mild stage of Alzheimer's disease. This concept is in line with the notion of a dissociation between preservation of olfactory and gustatory thresholds and an alteration in odor identification in patients with mild stage Alzheimer's disease, suggesting that the alteration is central rather than peripheral. Our findings suggest that an alteration of the associative level of gustatory information processing can be found in Alzheimer's disease early stage.

Aged↗
PubMed1994

[The psychophysics of sweet taste. 5. The use of a sequential staircase method for the determination of equally intense concentration pairs].

The suitability of a sequential staircase-method for the determination of equal stimuli of the gustatory sense is experimentally investigated. The aim is the decrease of experimental expenditure when ruling sources of bias. In order to realize them sucrose solutions are used both for the constant stimulus and also for the sequence of stimuli. Possible factors are the gradation of the sequence of stimuli and its displacement towards the constant stimulus. These are factorized in a two-staged trial arrangement and are interpreted in a form of an analysis of variance. The gradation of sequence (grain) is the key factor. It defines both the occasional bias and also the efficiency of systematical sources of bias. Thus the subject-depending judgement errors, which occur in larger gradation, are avoidable with their adjustment on the half of the difference threshold. The errors, which are due to the direction, are counterbalanced through an up and down trial execution with a following meaning average. A remaining influence of the displacement of sequence is normally neglective. The standard deviation for the single determination lies--independently of the concentration level--dimensionally slightly above the half of the setting grain. The method of constant stimuli requires at least the twofold experimental expenditure for a similar result.

Adult↗
PubMed2000

Biophysical properties and responses to neurotransmitters of petrosal and geniculate ganglion neurons innervating the tongue.

The properties of afferent sensory neurons supplying taste receptors on the tongue were examined in vitro. Neurons in the geniculate (GG) and petrosal ganglia (PG) supplying the tongue were fluorescently labeled, acutely dissociated, and then analyzed using patch-clamp recording. Measurement of the dissociated neurons revealed that PG neurons were significantly larger than GG neurons. The active and passive membrane properties of these ganglion neurons were examined and compared with each other. There were significant differences between the properties of neurons in the PG and GG ganglia. The mean membrane time constant, spike threshold, action potential half-width, and action potential decay time of GG neurons was significantly less than those of PG neurons. Neurons in the PG had action potentials that had a fast rise and fall time (sharp action potentials) as well as action potentials with a deflection or hump on the falling phase (humped action potentials), whereas action potentials of GG neurons were all sharp. There were also significant differences in the response of PG and GG neurons to the application of acetylcholine (ACh), serotonin (5HT), substance P (SP), and GABA. Whereas PG neurons responded to ACh, 5HT, SP, and GABA, GG neurons only responded to SP and GABA. In addition, the properties of GG neurons were more homogeneous than those of the PG because all the GG neurons had sharp spikes and when responses to neurotransmitters occurred, either all or most of the neurons responded. These differences between neurons of the GG and PG may relate to the type of receptor innervated. PG ganglion neurons innervate a number of receptor types on the posterior tongue and have more heterogeneous properties, while GG neurons predominantly innervate taste buds and have more homogeneous properties.

Acetylcholine↗
PubMed2000

Capsaicin, acid and heat-evoked currents in rat trigeminal ganglion neurons: relationship to functional VR1 receptors.

Activation of primary trigeminal (TG) neurons by protons, capsaicin, or heat can evoke a variety of sensations, including tingling, stinging, warmth, and burning. Capsaicin and acid are trigeminal stimulants that are important in gustatory physiology. These stimuli can activate H(+)-gated ion channels and heterologously expressed VR1 receptors (vanilloid receptor 1). We have obtained evidence by using electrophysiological and pharmacological measurements on TG neurons that these three stimuli can activate many receptors, and we have determined the extent they behave similarly to VR1 receptors and H(+)-gated channels from the DEGenerin/ENaC superfamily. Whole-cell recordings from rat TG neurons revealed that protons evoked transient (Tp), sustained (Sp), and biphasic (TSp) currents. Tp currents had reversal potentials (Vr) of 24-45 mV, a pH(0.5) range from 5.5 to 6.5, and were inhibited by amiloride, suggesting the presence of functional H(+)-gated channels. Sp currents were inhibited by the VR1 antagonist capsazepine, had Vr's approximately 0 mV, and had pH(0.5) = 6.4. Capsaicin also activated transient (Tc), sustained (Sc), and biphasic (TSc) currents. At pH 5.9, the sensitivity of the Sc currents increased by about a factor of 10, which may partially account for the synergistic responses of acid in foods containing capsaicin. Heating TG neurons evoked a thermally active, capsazepine-inhibitable current with threshold temperature of 43 degrees C and Vr = 5 mV that is also present in neurons activated by and protons (Sp) and capsaicin (Sc). These data suggest that TG neurons have functional receptors that behave similarly to VR1. Activation of such receptors should result in a burning sensation, whereas activation of the transient and biphasic currents should result in other taste descriptors.

Acids↗
PubMed1994

Effects of chronic food restriction on prodynorphin-derived peptides in rat brain regions.

Chronic food restriction produces a variety of physiological and behavioral adaptations including a potentiation of the reinforcing effect of food, drugs and lateral hypothalamic electrical stimulation. Previous work in this laboratory has revealed that the lowering of self-stimulation threshold by food restriction is reduced by mu- and kappa-selective opioid antagonists. In the present study, the effect of chronic food restriction on levels of three prodynorphin-derived peptides, namely dynorphin A1-17 (A1-17), dynorphin A1-8 (A1-8) and dynorphin B1-13 (B1-13) were measured in eleven brain regions known to be involved in appetite, taste and reward. Food restriction increased levels of A1-17 in dorsal medial (+19.6%), ventral medial (+24.2%) and medial preoptic (+82.9%) hypothalamic areas. Levels of A1-17 decreased in the central nucleus of the amygdala (-35.1%). Food restriction increased levels of A1-8 in nucleus accumbens (+34.4%), bed nucleus of the stria terminalis (+24.5%) and lateral hypothalamus (+41.9%). Food restriction had no effect on levels of B1-13. A1-17 is highly kappa-preferring and the brain regions in which levels increased all have a high ratio of kappa: mu and delta receptors. A1-8 is less discriminating among opioid receptor types and the brain regions in which levels increased have a low ratio of kappa: mu and delta receptors. The present results suggest that food restriction alters posttranslational processing within the dynorphin A domain of the prodynorphin precursor, possibly leading to a change in the balance between kappa and non-kappa opioid receptor stimulation in specific brain regions.

Animals↗
PubMed1982

Acute and subacute symptoms among workers in the printing industry.

The study population comprised 52 male printers and 52 controls. Each person was interviewed about job history, general health, and work-related symptoms. Symptoms from eyes and airways, neurological symptoms, and general symptoms were recorded. A lung function test and a measurement of the sense of smell were also carried out. The printers had significantly more eye, airway, and neurological symptoms than the controls; the main complaints being irritation of eyes, nose, throat, and a reduced sense of taste. The neurological symptoms were disorders of vision, vertigo, feeling of intoxication, and headache. Furthermore, abdominal pain and flatulence occurred more often among the printers. The symptoms showed no relation to age or job seniority, but neurological and general symptoms were related to shift work. No difference in lung function was found between the two groups. The printers had a slightly lower threshold of smell than the controls. Although the total load due to organic solvents and dust in the air was far below legal limits, the number of magnitude of symptoms experienced by the printers exceeded what is supposed when norms for workroom exposure are set. It is suggested that either the irritative effects of solvents are underestimated or the assumption of additive effects when great numbers of solvents are found does not hold true. A reduction of the number of solvents by eliminating the most toxic solvents or by using dyes without solvents is suggested.

Adult↗
PubMed2005

Characterization of aroma compounds responsible for the rosy/floral flavor in Cheddar cheese.

The aroma-active compounds that contribute to the rosy/floral flavor in Cheddar cheese were characterized using both instrumental and sensory techniques. Two cheeses (>12 months old) with rosy/floral flavor and two Cheddar cheeses of similar ages without rosy/floral flavors were selected. After direct solvent extraction/solvent-assisted flavor evaporation and separation into neutral/basic and acidic fractions, samples were analyzed by gas chromatography-olfactometry with aroma extract dilution analysis. Selected compounds were quantified using internal standard methodology. Some of the intense aroma-active compounds in the neutral basic fraction of the rosy/floral cheeses included 2-phenethanol (rosy), phenylethyl acetate (rosy), and phenylacetaldehyde (rosy/floral). Quantification, threshold analysis, and sensory analysis of model cheeses confirmed that increased concentrations of phenylacetaldehyde and phenylacetic acid caused rosy/floral flavor when spiked into Cheddar cheese.

Acetaldehyde↗
PubMed1983

Gustation and ingestive behavior in the rat.

Gustatory deafferentation was produced by combined bilateral section of the chorda tympani and glossopharyngeal nerves and the pharyngeal branch of the vagus nerve. The procedure did not affect the condition of the mouth, impair orientation to sensory stimuli, or severely disrupt the consummatory sequence. Nevertheless, deafferented subjects showed reduced responsiveness to food and water, elevated QHCl aversion thresholds, and impaired feeding efficiency. Food and water intake and body weight remained below control levels for at least 40-50 days postoperatively. Food intake deficits were not observed when the rats were offered ad lib pablum, a result suggesting that increased palatability could compensate for decreased gustatory input. The order of recovery of food intake through different diet types suggests a heightened responsiveness to taste stimuli. The effects of gustatory deafferentation are compared with those seen after section of trigeminal orosensory nerves (Jacquin & Zeigler, 1983), and the differential contributions of oral "taste" and oral "touch" are discussed.

Animals↗
PubMed1999

Combined effects of carbon dioxide addition and barrier films on microbial and sensory changes in pasteurized milk.

The growth of psychrotrophic microorganisms is an important factor in the deterioration of refrigerated pasteurized milk. Dissolved CO2 inhibits certain spoilage microorganisms in foods provided that the packaging offers a sufficient barrier to CO2 evolution. The objectives of this work were, first, to estimate the sensory threshold for dissolved CO2 in 2% milk and, second, to determine the relationship between microbial growth and package barrier properties for pasteurized milk to which CO2 had been added at concentrations near the flavor threshold. The sensory threshold, as determined by a trained panel, for CO2 in 2% pasteurized milk was > 2.8 mM and < 9.1 mM. Pasteurized milk was inoculated with a cocktail of spoilage microorganisms, packaged in different barrier film pouches, and stored at 6.1 degrees C for up to 28 d. The addition of CO2 at concentrations of 8.7 and 21.5 mM increased the time needed to reach 10(6) cfu/ml from 6.4 d (no CO2) to 8.0 and 10.9 d, respectively, in low barrier pouches. In high barrier pouches, the time needed to reach 10(6) cfu/ml was increased to 9.7 and 13.4 d, respectively, at CO2 concentrations of 8.7 and 21.5 mM. This increase represents an increase in shelf-life of approximately 25 to 200%. Microbial counts had longer lag times and lower growth rates and took longer to reach stationary growth as the concentration of CO2 increased in all films than did the control milk. The control milk curdled in less than 17 d, but the test milk in the high barrier packaging had not curdled at 28 d. These data suggest that the shelf-life of pasteurized refrigerated milk could be extended by at least 25 to 200% at CO2 concentrations near the sensory threshold. The major variables in shelf-life are the amount of added CO2 and the barrier properties of the package.

Animals↗
PubMed1993

Large enhancement of canine taste responses to amino acids by salts.

The effects of salts on the canine taste responses to amino acids were examined by recording the activity of the chorda tympani nerve. 1) The tonic responses to most amino acids examined were significantly enhanced by the presence of various salts. 2) The degree of the enhancement varied with the species of amino acid and salt. The responses to most amino acids were enhanced by sodium, potassium, and calcium salts, but not enhanced by magnesium salts. The response to methionine, for example, was enhanced by NaCl, but not by Na phosphate of equimolar Na+. 3) The responses to glycine and alanine were suppressed by high concentrations of NaCl. 4) The presence of salts (NaCl and CaCl2) enhanced the responses to amino acids without affecting the thresholds for the amino acids, suggesting that the presence of the salts did not change the affinity of amino acids to the receptor sites. 5) The enhancing effects of salts on the responses to amino acids could not be explained in terms of permeability of cation and anion of salts. It was speculated that the binding of cation and anion of salts on the receptor membranes induces exposure of the receptor sites for amino acids available for binding of amino acids.

Amino Acids↗
PubMed1982

Taste preferences for amino acids in the house musk shrew, Suncus murinus.

Taste preferences in house musk shrews for amino acids as well as NaCl, sucrose, quinine hydrochloride, HCl and saccharin Na were studied by employing the two-bottle preference technique. Shrews showed a preference for 0.2--05. M sucrose but a moderate rejection to NaCl and a strong rejection to quinine, HCl and saccharin. They exhibited a marked preference for many naturally occurring L-alpha-amino acids with aliphatic side chains at both 0.02 and 0.2 M. Increase in the aliphatic side chain length of DL-alpha-amino acids resulted in both lowering of the preference threshold and increase in the preference magnitude. Amino acids with side chains containing sulfur atoms, basic groups and Phe at 0.02 M were preferred to water, but Cys and Arg at 0.2 M was rejected. Shrews showed neither preference nor rejection to Trp, Asn, Gln and monosodium glutamate at 0.02 M, but rejected strongly Asp and Glu. D-Met from 0.001 to 0.1 M was preferred as well as L-Met, while D-Phe was more preferred than L-Phe. Such preferences for a wide variety of amino acids in shrews could be attributed to their food habit of predating on various kinds of insects and worms.

Amino Acids↗
PubMed2004

Treatment of taste and odor material by oxidation and adsorption.

Massive blooms of blue-green algae in reservoirs produce the musty-earthy taste and odor, which are caused by compounds such as 2-MIB and geosmin. 2-MIB and geosmin are rarely removed by conventional water treatment. Their presence in the drinking water, even at low levels (ng/L), can be detected and it creates consumer complaints. So those concentrations have to be controlled as low as possible in the drinking water. The removals by oxidation (O3, Cl2, ClO2) and adsorption (PAC, filter/adsorber) were studied at laboratory and pilot plant (50 m3/d) to select suitable 2-MIB and geosmin treatment processes. The following conclusions were derived from the study. Both of the threshold odor levels for 2-MIB and geosmin appeared to be 30 ng/L as a consequence of a lab test. For any given PAC dosage in a jar-test, removal efficiencies of 2-MIB and geosmin were increased in proportion to PAC dosage and were independent of their initial concentration in raw water for the tested PAC dosages. In comparison of geosmin with 2-MIB, the adsorption efficiency of geosmin by PAC was superior to that of 2-MIB. The required PAC dosages to control below the threshold odor level were 30 mg/L for geosmin and 50 mg/L for 2-MIB at 100 ng/L of initial concentration. Removal efficiencies of odor materials by Cl2, ClO2, and O3 were very weak under the limited dosage (1.5 mg/L), however increased ozone dosage (3.8 mg O3/L) showed high removal efficiency (84.8% for 2-MIB) at contact time 6.4 minutes. According to the initial concentrations of 2-MIB and geosmin, their removal efficiencies by filter/adsorber differed from 25.7% to 88.4%. For all those, however, remaining concentrations of target materials in finished waters were maintained below 30 ng/L. The longer run-time given for the filter/adsorber, the higher the effluent concentration generated. So it is necessary that the run-time of the filter/adsorber be decreased, when 2-MIB or geosmin occurs in raw water.

Adsorption↗