Taste thresholds

W. H. Stahl, ed.. Compilation of Odor and Taste Threshold Values Data, DS 48, Amehcan Society for Testing Matehals, Philadelphia, Pa., 1973. 

Where the TDS in water supphes is above the taste threshold, or where there is concern about the safety of the water supply, simple RO systems operating on line pressure have made a major impact. These compac t units are usually kitchen installed, and are simple, small, and cheap. For typical line pressure of 400 kPa, 95 percent reduction of TDS is feasible if the inlet concentration is below 2000 mg/ . 

Taste Threshold of Bitter Compounds, and Equilibrium Constants of Binding of Bitter Compounds by a Bitter-sensitive Protein ... 

The importance of lipophilicity to bitterness has been well established, both directly and indirectly. The importance of partitioning effects in bitterness perception has been stressed by Rubin and coworkers, and Gardner demonstrated that the threshold concentration of bitter amino acids and peptides correlates very well with molecular connectivity (which is generally regarded as a steric parameter, but is correlated with the octanol-water partition coefficient ). Studies on the surface pressure in monolayers of lipids from bovine, circumvallate papillae also indicated that there is a very good correlation between the concentration of a bitter compound that is necessary in order to give an increase in the surface pressure with the taste threshold in humans. These results and the observations of others suggested that the ability of bitter compounds to penetrate cell membranes is an important factor in bitterness perception. 

Several of the lower molecular weight aliphatic compounds, in a mixture, are part of the roasted coffee aroma. A nine-compound mixture with roasted coffee aroma contained isopentane, n-hexane, acetaldehyde, dimethyl sulfide, propanal, isobutanal, isopentanal, methanol, and 2-methylfuran.20 In addition, the freshness of aroma and taste has been correlated with 2-methylpropanal and diacetyl. When the concentration of these falls off, so does the taste.21 Other aliphatic compounds that are steadily lost from ground roasted coffee, unless it is vacuum packaged, include methyl formate, methyl acetate, methyl thioacetate, and acetone.22 The concentrations in roast coffee for four compounds whose contribution to the fresh flavor have long been known are dimethyl sulfide (4 ppm), methyl formate (12 ppm), isobutanal (20 ppm), and diacetyl (40 ppm). The taste thresholds are 0.1, 0.5, 0.5, and 1.0 ppm, respectively, in the brew made with 5 g coffee per 100 ml water.15... 

The human taste threshold for PCP in drinking water is about 30 pg/L (USEPA 1980), a level far below the upper safe limit of 1.01 mg/L and near the no-observable-effect level of 21 pg/L (Table 23.7). Odor detection is not as sensitive as taste the odor threshold for PCP ranges from about 857 pg/L at 30°C, to 1600 pg/L at 20 to 22°C, to 12,000 pg/L at 60°C (USEPA 1980). It is not clear whether the determined organoleptic threshold values made the water undesirable or unfit for consumption (USEPA 1980). If fish and wildlife species of concern have PCP organoleptic thresholds that are similar to those of humans, or lower, will they too avoid contaminated habitats or diets ... 

Fazzalari FA. 1978. ASTM/DS-48A Compilation of odor and taste threshold values. 58... 

Actually when the subject is studied carefully, it becomes evident that ability to taste PTC is not definitely a positive or negative matter people differ widely in their taste thresholds for the substance. The tasters are able to taste low concentrations the nontasters require much higher levels but are in general able to taste it in highly concentrated solution. 

One might suppose on the basis of the amount of attention PTC has received that it is quite a unique substance in its ability to elicit different responses from different individuals. Actually this is not the case at all since wide interindividual differences in taste threshold and taste reactions can be observed with almost anything that can be tasted. Hundred-fold variations in taste thresholds are very common (even when small groups are studied) with respect to substances like sodium or potassium chlorides or hydrochloric acid.41 Saccharine, quinine, cascara, and mannose are among the substances, in addition to creatine mentioned above, for which individuals are known to show highly diverse taste reactions.42 Richter found some children who could not taste 20 per cent sugar solutions.43... 

One of the interesting observations which may be made in connection with taste-testing is that some individuals appear to have higher stable taste thresholds and others show much greater variability when repeated tests are made. Sufficient studies have not been carried out to ascertain how general or how striking these differences in variability are. 

Certain miscellaneous observations have a bearing on our discussion of differences in taste reactions. For example, it is well recognized in hospitals that, although a barium sulfate emulsion is perfectly tasteless and innocuous to many individuals, to others it is very disagreeable. It would appear that the taste threshold for barium sulfate varies from individual to individual and that this substance is soluble enough to give a sensation of taste to some individuals. 

API. Review of Published Odor and Taste Threshold Values of Soluble Gasoline Components, API Publication No. 4419 (Washington, DC American Petroleum Institute, 1985). 

Clear, colorless, corrosive liquid with a strong vinegar-like odor and very sour taste. Odor threshold concentrations of 1.0 ppmv and 6.0 ppby were reported by Leonardos et al. (1969) and Nagata and Takeuchi (1990), respectively. Shaw et al. (1970) reported a taste threshold in water of 100 ppm. 

White to light tan crystals with a bleach-like type odor. At 40 °C, the average odor threshold concentration and the lowest concentration at which an odor was detected were 280 and 37 pg/L, respectively. At 25 °C, the average taste threshold concentration and the lowest concentration at which a taste was detected were 140 and 44 pg/L, respectively (Young et ah, 1996). 

Colorless liquid with an aromatic odor. Experimentally determined detection and recognition odor threshold concentrations were 40 pg/m (8 ppbv) and 230 pg/m (47 ppbv), respectively (Heilman and Small, 1974). The taste threshold concentration in water is 60 ppb (Young et al, 1996). 

Table 17. Lowest Taste Threshold Concentrations of Organic Compounds in Water... 

Alexander, H.C., McCarty, W.M., and Bartlett, E.A., and Syverud, A.N. Aqueous odor and taste threshold values of industrial chemicals, / Am. Water Works Assoc., 74(ll) 595-599, 1982. 

Flavor (odor + taste), 0 odor only. 0 odor threshold (medium given), T taste threshold (medium given). 

Compound pH before adjusting to 6 Na+/Peptide (mMAnM) Taste Threshold Value (mM)... 

For estimating the contribution of volatile compounds to bread aroma Rothe and coworkers (S) defined "aroma value" as the ratio of the concentration of some volatile compounds to the taste threshold value of the aroma. This concept was further developed by Weurman and coworkers (9) by introducing "odor value", in which aroma solutions were replaced by synthetic mixtures of volatile compounds in water. These mixtures showed the complexity of the volatile fractions of wheat bread, because none of them resembled the aroma of bread. Recently two variations of GC-sniffing were presented (10-11), in which the aroma extract is stepwise diluted with a solvent until no odor is perceived for each volatile compound separately in the GC effluent. The dilution factors obtained indicate the potency of a compound as a contributor to the total aroma. 

Fazzalari FA (ed) (1978) Compilation of Odor and Taste Threshold Data. ASTM Data Series DS 48A. American Society for Testing and Materials, Philadelphia... 

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