Threshold odor number

Taste and Odor. The measurement of taste and odor is somewhat subjective and depends on the personal judgements of individuals. Panels of not less than five observers, and preferably more than ten, are used. The sample is diluted with odor-free water until a ratio at which the odor is just perceptible is determined this ratio is called the threshold odor number (TON). A similar method is used to detect a distinct taste in water (see Flavor characterization). ... 

Color is measured in color units and based on platinum cobalt units (PCU) for comparative purposes. Odor is measured by the threshold odor number (TON), based on the number of dilutions with odor-firee water necessary to cause the odor to be nondiscemible in warmed water under prescribed conditions. 

Odor affects the drinkability of water. It is measured by the threshold odor number (TON). This is the dilution factor necessary before the odor is perceptible. A TON of 1 indicates that the water has characteristics comparable to odor-free water. 

It is sometimes difficult to identily the actual cause of odor and taste problems in water. Some of common odor- and taste-causing compounds include hydrogen sulfide (H2S), methane, algae, oils, phenols, cresols, and volatile compounds. Removal of taste and odor problems is a common application for the water aeration process. The process is suitable for H2S, methane, and volatiles, but not for algae and oils, phenols, and cresols. The compounds must be volatile for aeration to be effective. Aeration is appropriate for many industrial compounds. A classic installation is at Nitro, WV, which utilizes aeration and granular activated carbon (GAC). The raw water had threshold odor numbers (T.O.N.) of 5000-6000 from industrial contamination. The process was effective for reducing the taste and odor down to levels of 10-12 T.O.N. Although taste and odor applications are most common, there are many other tastes and odors that simply cannot be removed by aeration alone, which may explain why so many early plants were abandoned (1-10). 

Taste and odor No health-based guideline value. The threshold odor number (TON) is the greatest dilution of sample with odor-free water yielding definitely perceptible odor SC No value set 3TCN Flavor profile analysis... 

From threshold odor number (TON) HDPE and PEX show odor (TON > 4)... 

The long-held dichotomy of macrosmatic and microsmatic vertebrates is no longer tenable. Neuroanatomists had assumed that taxa with relatively few olfactory receptor cells and small olfactory bulbs would also be inferior in olfactoiy performance (threshold and number of compounds detected) to those with more receptors and larger bulbs. However, we now know from single-cell recordings that a particular receptor cell type can respond to a wide range of odor compounds that share certain features. Keverne (1983) pointed out that the olfactory bulbs act as a filter, while more complex pattern analysis takes place in the neocortex. The more evolved the neocortex, as in primates, the... 

The TON is the number of times a given volume of the gaseous sample is to be diluted in clean air to bring it to the threshold odor level determined by 50% of a panel of observers. Its intensity is expressed in odor units. 

The last set of requirements in olfactometry is concerned with the differences between panel members. People vary widely in their sensitivity. A factor of a 100 between the thresholds of two subjects for the same substance is not uncommon. For a number of substances, specific anosmia s or specific hyposmia s are found. In such cases a person has no sensitivity at all or a very high threshold for the given substance, but normal sensitivity to other substances (1). This is an illustration of the fact that sensitivity to odours is specific rather than general. This is also demonstrated by Punter (2, 3) who determined the thresholds of 69 odorous substances for the same group of subjects and calculated the correlations between these thresholds (see figure 2). 

Specific odorants such as VFA, TIP or individual compounds can be used to indicate odour offensiveness but their absence does not give any information about the possiblity of other odorants being present. The offensive odours of treated slurry, which did not contain the 6 VFA, 3 phenols, 2 indoles or ammonia, were due to compounds not determined in these experiments. There are a large number of other odorants cited with very low threshold levels (28 29) which could be responsible for this odour offensiveness. Since the odour offensiveness test is so subjective any indicator must have... 

Since the publication of the third edition, additional data have been critically reviewed. New or additional data included in this edition are bioconcentration factors, aquatic mammalian toxicity values, degradation rates, corresponding half-lives in various environmental compartments, ionization potentials, aqueous solubility of miscellaneous compounds, Henry s law constants, biological, chemical, and theoretical oxygen demand values for various organic compounds. Five additional tables have been added Test Method Number Index, Dielectric Values of Earth Materials and Fluids, Lowest Odor Threshold Concentrations of Organic Compoimds in Water, and Lowest Threshold Concentrations of Organic Compounds in Water. 

In addition to 75% monoterpene hydrocarbons (Oa-pinene 5-21% /7-pinene 40-70% 3-carene 2-16%) and ca. 10% sesquiterpene hydrocarbons, galbanum oil contains a fairly large number of terpene and sesquiterpene alcohols and their acetates. Minor components, with entirely different structures and low odor threshold values, contribute strongly to the characteristic odor [284a, 515-519]. Examples are as follows ... 

Odor activity values The number of times an odorant is present above its threshold as measured in the food matrix... 

The detection frequency method uses a number of sniffers to quantify an odor in the GC effluent from a single concentration. The underlying assumption is that any random sample of sniffers will functionally express a range of sensitivities, so that some sniffers will detect an odor and others will not. The conclusion is that the fraction of a group that detects an odor is related to the group potency of the odor, a notion that can be supported by the large diversity in odor thresholds observed in humans. 

Furthermore, as an extract of a natural product is concentrated, the number of odorants detected increases indefinitely. Clearly, most of the odorants in a natural product are below their odor threshold, and it is only the most potent compounds that are involved in generating the flavor response. An odorant can be very potent at extremely low concentrations if it has an extremely low odor threshold, (unit go). In practice, early GC/O analysts attempted to concentrate the sample as far as possible to identify as many potential odorants as possible. Compositional studies combined with threshold studies were then used to sort out the important odorants from the ones that did not contribute to the flavor experience. Rothe s odor units (OU = concentration in sample/threshold in sample) were an early attempt to rank odorants by potency. The process of determining OU values for a food required a lot of chemical and psychophysical analysis. Dilution analysis was developed to produce an OU-like value directly from GC/O without the need to know the identity of the odorant. In fact, the real value of dilution analysis is that it can tell the analyst which compounds to identify. 

It is well known for example in the saturated LDPE polymer chains that a certain number of double bounds exist which can be measured with IR spectroscopy. By extraction with non-polar solvents and GC separation, numerous alkanes and alkenes can be identified which are dissolved in small concentrations in the PE. The odor thresholds of these compounds are in general so high that these hydrocarbons play no sensory role. As a result no correlation can be made between the total amount of volatile compounds isolated from PE or the fingerprint chromatogram from a GC separation and the sensory properties of a sample. The relevant sensory compounds as a rule are the (order of magnitude) less concentrated oxygenated compounds in the... 

Tabic 13-4 Absolute odor thresholds (ng) and OTa concentrations (mg/m3) of alkenes and the corresponding alcohols and unsaturated carbonyl compounds. The number of C-atomes in the molecule is designated with n. 

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