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At least 73 records · Page 4Linked to original sources
PubMed2003

A comparison of taste thresholds for sweet and astringent-tasting compounds in great apes.

Taste responses to fructose and tannic acid were compared between great apes using the 'two-bottle test' with tests of brief duration. The taste thresholds for fructose were [10-20] mM in Pongo pygmaeus, [40-50] mM in Pan troglodytes, and [70-80] mM in Gorilla gorilla. Inhibition thresholds for tannic acid were [2.9-3.5] mM in Pongo and [2.9-5.9] mM in Pan. Gorillas apparently significantly preferred tannins at low concentrations ([0.59-5.9] mM) but rejected concentrations above [8.8-14.7] mM. These results are discussed in relation to the effects of phylogenetic inertia and biological adaptation.

Animals↗
PubMed2005

Polyphenols: factors influencing their sensory properties and their effects on food and beverage preferences.

Bitterness and astringency are found in a variety of foods, including nuts, fruits, chocolate, tea, wine, and soymilk. In fruits and beverages, the taste of bitterness and the tactile sensation of astringency are elicited primarily by flavanol polymers (proanthocyanidins or condensed tannins). Variations in proanthocyanidin composition, such as polymer size, extent of galloylation, and formation of derivatives, affect both bitterness and astringency. In beverages, other factors also influence these sensations, including the pH and the levels of ethanol, sweetness, and viscosity. Similarly, foods eaten with beverages can influence astringency. For example, eating dark chocolate increases the astringency of red wine more than does milk chocolate. Individuals perceive astringency differently because of variations in salivary flow rates, and preferences for and acceptance of a product may vary tremendously among individuals; decreasing bitterness and/or astringency may not increase preference. Factors influencing bitterness, astringency, and individual preference decisions are discussed.

Consumer Behavior↗
PubMed2006

Molecular definition of the taste of roasted cocoa nibs (Theobroma cacao) by means of quantitative studies and sensory experiments.

Sensory-guided decomposition of roasted cocoa nibs revealed that, besides theobromine and caffeine, a series of bitter-tasting 2,5-diketopiperazines and flavan-3-ols were the key inducers of the bitter taste as well as the astringent mouthfeel imparted upon consumption of roasted cocoa. In addition, a number of polyphenol glycopyranosides as well as a series of N-phenylpropenoyl-l-amino acids have been identified as key astringent compounds of roasted cocoa. In the present investigation, a total of 84 putative taste compounds were quantified in roasted cocoa beans and then rated for the taste contribution on the basis of dose-over-threshold (DoT) factors to bridge the gap between pure structural chemistry and human taste perception. To verify these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of the individual taste compounds in their "natural" concentrations. Sensory analyses revealed that the taste profile of this artificial cocktail was very close to the taste profile of an aqueous suspension of roasted cocoa nibs. To further narrow down the number of key taste compounds, finally, taste omission experiments and human dose/response functions were performed, demonstrating that the bitter-tasting alkaloids theobromine and caffeine, seven bitter-tasting diketopiperazines, seven bitter- and astringent-tasting flavan-3-ols, six puckering astringent N-phenylpropenoyl-l-amino acids, four velvety astringent flavonol glycosides, gamma-aminobutyric acid, beta-aminoisobutyric acid, and six organic acids are the key organoleptics of the roasted cocoa nibs.

Cacao↗
PubMed1994

Bitterness in wine.

Bitterness in wine is elicited primarily by flavonoid phenols, which are bitter and astringent, and by ethanol. Monomeric flavonoid phenols are primarily bitter but as the molecular weight increases upon polymerization, astringency increases more rapidly than bitterness. The chiral difference between the two wine flavan-3-ol monomers produces a significant difference in temporal perception of bitterness: (-)-epicatechin is significantly more bitter and had significantly longer duration of bitterness than (+)-catechin. Ethanol enhances bitterness intensity and duration, whereas varying wine pH has little or no effect on perceived bitterness. Whereas PROP status had no significant effect on temporal perception of bitterness or astringency, subjects with low salivary flow rates took longer to reach maximum bitterness and astringency intensity and reported longer persistence of both attributes than high-flow subjects.

Ethanol↗
PubMed2005

Quality components of sea buckthorn (Hippophae rhamnoides) varieties.

The sensory quality and chemical constituents of juices from seven sea buckthorn (Hippophaerhamnoides L.) varieties were studied in two consecutive seasons. The juices were generally described as sour and astringent, with low sweetness and fruity flavor. The differences in sensory quality as well as in chemical composition between samples and years were significant (p < 0.05) in most parameters studied. The Chuiskaya variety was described as the sweetest, with the strongest fruity flavor, whereas the varieties Avgustinka, Botanicheskaya, Trofimovskaya, and Raisa were the sourest and most astringent. Total sugar (fructose and glucose) varied from 1.9 to 7.1 g/100 mL in juice, total acid (malic and quinic acids) from 3.1 to 5.1 g/100 mL, vitamin C from 29 to 176 mg/100 mL, and pulp oil from 0.7 to 3.6%. The soluble solids were between 7.4 and 12.6, the pH between 2.7 and 2.9, and the titrable acidity between 2.0 and 3.7. The redness was highest on Avgustinka and Raisa, but there were no differences in yellowness. Total sugar and the sugar/acid ratio correlated positively with sweetness and negatively with sourness and astringency, whereas total acid and titrable acidity correlated positively with sourness and astringency and negatively with sweetness.

Adult↗
PubMed2005

Molecular definition of black tea taste by means of quantitative studies, taste reconstitution, and omission experiments.

Recently, bioresponse-guided fractionation of black tea infusions indicated that neither the high molecular weight thearubigens nor the theaflavins, but a series of 14 flavon-3-ol glycopyranosides besides some catechins, might be important contributors to black tea taste. To further bridge the gap between pure structural chemistry and human taste perception, in the present investigation 51 putative taste compounds have been quantified in a black tea infusion, and their dose-over-threshold (Dot) factors have been calculated on the basis of a dose/threshold relationship. To confirm these quantitative results, an aqueous taste model was prepared by blending aqueous solutions of 15 amino acids, 14 flavonol-glycosides, 8 flavan-3-ols, 5 theaflavins, 5 organic acids, 3 sugars, and caffeine in their "natural" concentrations. Sensory analyses revealed that the taste profile of this artificial cocktail did not differ significantly from the taste profile of the authentic tea infusion. To further narrow the number of key taste compounds, finally, taste omission experiments have been performed, on the basis of which a reduced recombinate was prepared containing the bitter-tasting caffeine, nine velvety astringent flavonol-3-glycosides, and the puckering astringent catechin as well as the astringent and bitter epigallocatechin-3-gallate. The taste profile of this reduced recombinate differed not significantly from that of the complete taste recombinate, thus confirming these 12 compounds as the key taste compounds of the tea infusion. Additional sensory studies demonstrated for the first time that the flavanol-3-glycosides not only impart a velvety astringent taste sensation to the oral cavity but also contribute to the bitter taste of tea infusions by amplifying the bitterness of caffeine.

Amino Acids↗
PubMed2004

Effects of purified persimmon tannin and tannic acid on survival and reproduction of bean bug, Riptortus clavatus.

We evaluated the effects of tannic acid and purified perrsimmon tannin on survival and reproduction of bean bugs, Riptortus clavatus.Feeding behavior of R. clavatus was also examined on sweet (cv. Fuyu) and astringent (cv. Chongdosi) persimmon fruits. Soluble tannin in sweet persimmon fruits decreased from 3% in early June to 0.5% in late September, but it increased from 2 to 8% during the same period in astringent persimmon fruits. More bugs visited sweet than astringent persimmon. Numbers of piercing/sucking spots were higher on sweet than on astringent persimmon. When fed 1 and 3% solutions of persimmon tannin, adult bugs ingested only 64.1 and 9.5% of the amount of water ingested by those offered the control (distilled water). Amounts of persimmon tannin ingested by the adult bugs were 6.5 and 2.8 times higher at 1 and 3% tannin solutions compared to a 0.1% solution. Persimmon tannin exerted negative effects on survival and reproduction of R. clavatus at higher concentrations (1 and 3% solutions). Feeding of R. clavatus adults decreased with increasing tannin concentrations. When results from both sexes were pooled, 50% mortality was achieved at 11 and 4 days after treatment with the 1 and 3% tannin solutions, respectively. Reproduction decreased with 1% tannin, and no eggs were produced with 3% tannin solution. Tannic acid was similar in its effects on R. clavatus. All nymphs died 14, 12, and 7 days after feeding on 0.1, 1, and 3% tannic acid, respectively. Adults were less sensitive than nymphs, and their survival was not affected by 0.1% tannic acid. However. 1 and 3% tannic acid solutions were fatal. Survivorship decreased to 50% at 11 and 6 days after supplying tannin solutions of 1 and 3% concentrations. Higher concentrations (1 and 3%) resulted in reduced reproduction, as was seen with persimmon tannin. Our data may explain why R. clavatus does not invade sweet persimmon orchards until late July, when concentrations of soluble tannin are low enough to allow them to feed.

Animals↗
PubMed2005

Qualitative differences of divalent salts: multidimensional scaling and cluster analysis.

Sensations from salts of iron, calcium, magnesium, and zinc with different anions were studied using a sorting task and multidimensional scaling (MDS). Ten divalent salts were adjusted in concentrations such that the mean intensity ratings were approximately equal. Stimuli were sorted on the basis of similarity to minimize any semantic influence and were examined with and without nasal occlusion to eliminate retronasal cues. Compounds representing the four primary tastes and astringency were also sorted. Similarity estimates were derived from sorting and were submitted to MDS. Divalent salts fell outside the area of the space defined by the four primary tastes. The nose-open condition showed that some of the divalent salts have unique metallic sensations along with astringency. The groupings obtained were corroborated using single-linkage cluster analysis. An iron group was most distinctive in metallic sensations; calcium and magnesium salts were primarily bitter; and zinc salts were characterized by astringency. When nasal cues were not available, the sensations from the divalent salts were mainly explained by bitterness and astringency. Results were consistent with a previous evaluation of divalent salts using descriptive analysis.

Adult↗
PubMed2005

[Chemical and sensory characterization of tea (Thea sinensis) consumed in Chile].

By means of descriptive analysis four varieties of tea (Thea sinensis) were assesed: Argentinean OP (orange pekoe) tea (black), Brazilian OP tea (black), Ceylan OP tea (black) and Darjeeling OP tea (green). The appearance of dry tea leaves were qualitatively characterized comparing with dry leaves standard. The attributes: colour, form, regularity of the leaves, fibre and stem cutting were evaluated The differences obtained were related to the differences produced by the effect of the fermentation process. Flavour and aroma descriptors of the tea liqueur were generated by a trained panel. Colour and astringency were evaluated in comparison with qualified standards using non structured linear scales. In order to relate the sensory analysis and the chemical composition for the different varieties of tea, following determinations were made: chemical moisture, dry material, aqueous extract, tannin and caffeine. Through multifactor regression analysis the equations in relation to the following chemical parameters were determined. Dry material, aqueous extract and tannins for colour and moisture, dry material and aqueous extract for astringency, respectively. Statistical analysis through ANOVA (3 variation sources: samples, judges and replications) showed for samples four significant different groups for astringency and three different groups for colour. No significant differences between judges or repetitions were found. By multifactor regression analysis of both, colour and astringency, on their dependence of chemist results were calculated in order to asses the corresponding equations.

Analysis of Variance↗