Odor quality

The mammalian olfactory system possesses enormous discriminatory power. It is claimed that humans can perceive many thousands of different odorous molecules, termed odorants. Even slight alterations in the structure of an odorant can lead to profound changes in perceived odor quality. One commonly cited example is carvone, whose L- and D-stereoisomers are perceived as spearmint and caraway, respectively. However, more subtle molecular alterations can also generate striking changes in perception. 

Newborns respond to odors by rapid breathing and activity changes. They can detect odors, rapidly develop their sensitivity over the first 4 days of life (Lipsitt etal, 1963), discriminate odor qualities and intensities, memorize odors for 1 day (and possibly for life), prefer odors they had experienced earlier, and localize odor sources (e.g. newborns aged 1 to 5.5 day olds turn away from a cotton swab with ammonia Rieser eta/., 1976). Neonates younger than 12 hours show olfactory preferences and aversions even before they experience their first food. 

Enantiomeric compounds differ from one another only in two aspects The chiroptical characteristics (optical rotation) and the speed of their reaction with chiral molecules. The human olfactory organ is also capable of distinguishing chiral molecules. The odor quality and potency of enantiomeric compounds may show considerable differences. Thus, distinct differentiation in odor perception could be observed in the pairs of enantiomeric oxygenated monoterpenoid odorants. " However, the... 

The odor quality and strength of the two citronellol enantiomers were found to be different.The (35)(—)-enantiomer (Rhodinol) possesses a much finer rose odor than the (3i )(+)-enantiomer. (35)(-)-Citronellol has a sweat, peach-like flavor, while (3i )(- -)-citronellol has a bitter taste. (35 )(—)-Citronellol has been found in a number of geranium and rose oils. (3i )(+)-Citronellol occurs in the oils of Ceylon and Java citronella, Cymhopogon winttrianusff Boronia citriodora. Eucalyptus citriodoraff geranium, Spanish verbena and others. Because of the... 

Compounds used in the database were obtained from literature reports of chemical structure and odor quality (7-11). In Table 1, a list of the compounds comprising the database is given. The macrocyclic and nitroaromatic musks are of strong, medium, weak, or unspecified odor intensity the nonmusks are odorless or have an odor other than musk. Information about odor quality and intensity is contained in the activity label associated with each compound. It should be emphasized that a musk compound labeled as weak, medium, or strong refers only to the change in its odor threshold, not to any change in its odor quality. Structural classes present in the dataset are shown in Fig. 1. Natural musks, whose sources include both rare animal and plant species, are... 

A prediction set of 19 compounds (see Table 2) was used to assess the predictive ability of the 15 molecular descriptors identified by the pattern recognition GA. We chose to map the 19 compounds directly onto the principal component plot defined by the 312 compounds and 15 descriptors. Figure 5 shows the prediction set samples projected onto the principal component map. Each projected compound lies in a region of the map with compounds that bare the same class label. Evidently, the pattern-recognition GA can identify molecular descriptors that are correlated to musk odor quality. 

The odor of ambergris, urine, sandalwood, and musk are believed to be related to their distinct structures, and small structural modifications can influence decisively the odor quality and potency. There are three different classes of musk that are not related in structure ... 

A very specific relationship exists between chemical structure and odor quality this has been defined for a number of odorant classes, for example steroids and mu compounds (76). The chirality as well as the flexibility of a molecule is also important in deling the odor. A structure that can assume different conformations could interact with more than one receptor type and elicit more than one odor quality. Thus one typically observes several odor descriptors used for compounds... 

Greenberg, M.J. In Odor Quality and Qiemical Structure Moskowitz, H.R. Warren, C.B., Eds. ACS Symposium Series 148 Amoican Chemical Society Washington, D.C., 1981 pp 177-194. 

Geosmin synthesis in channel catfish aquaculture systems, 322-333 biosynthesis, 328-329 occurrence in organisms, 324,325r odor quality, 13 synthesis, 322,323/ synthetic mutant selection, 330-333 Glucosyloxyethyl methacrylate polymerization, 224,225/ synthesis and toxicity, 222,224 Glucosyloxyethyl methacrylate polymers potential applications, 226r properties, 224-227... 

Currently, large-scale synthesis of terpenoids permits production without the uncertainties associated with isolation from natural sources. However, the odor qualities of synthetic products often differ from those of compounds isolated from natural sources, since the desired natural product often is not separated from small amounts of compounds with similar physical properties but different odor quality. 

A product with a higher geraniol content and slightly different odor quality for use in fine fragrances is obtained by fractionating palmarosa oil after saponification of the geranyl esters. 

Production. (—)-Citronellol is still obtained mainly from geranium oil by saponification followed by fractional distillation. Although of high odor quality, it does not possess the true (—)-citronellol odor due to impurities. Much larger quantities of (+)- and (zb)-citronellol are used and are prepared by partial or total synthesis. 

Rychlik M, Schieberle P, Grosch W (1998) Compilation of Odor Thresholds, Odor Qualities and Retention Indices of Key Food Odorants. Deutsche Forschungsanstalt fuer Lebensmit-telchemie, Garching... 

Four studies are described here that relate physicochemical properties to odor quality as defined by maps derived by multidimensional scaling procedures. The mathematical procedures used to relate the physicochemical properties to the maps are discussed as well. 

Figure 1. Two-dimensional space for a "broad range of odorants. Compounds located close to one another have similar odor quality (from Ref. h).

These examples are merely modest beginnings at relating geometrical maps that represent similarities in odor quality with physicochemical parameters. It is now necessary to expand these mathematical techniques to more data sets with extensive use of the non-covalent bonding parameters shown in Table 1. Ultimately reliable design of flavor molecules by computer will be feasible as ve explore a wider range of molecular types, especially isomers, with the techniques described in this paper. 

The second pattern of temporal fragrance variation is the change in odor quality or quantity following pollination. Many plants entirely cease odor production within minutes (Catasetum see above) to hours (Nicotiana attenuata Euler and Baldwin,... 

Because of factors of low cost, stability, and odor quality, PEA is ideally suited for use in bar soap fragrances where its use can be up to 30—50% of the fragrance. 

Industry has standardized procedures for the quantitative sensory assessment of the perceived olfactory intensity of indoor malodors and their relationship to the deodorant efficacy of air freshener products. Synthetic malodors are used for these evaluation purposes. These malodors should be hedonically associated to the reaT malodor, and must be readily available and of consistent odor quality. These malodors should be tested in various concentrations and be representative of intensities experienced under normal domestic conditions. Panelists are trained to evaluate malodor intensity and the degree of modification. 

Contains retention indicies on 4 substrates, CAS numbers, and odor qualities for over 400 chemicals identified by GC/O in food. 

Verification requires sniffing an authentic standard to verify that the component and the standard have the same retention index and odor quality. Table G 1.8.1 shows the result obtained when sniffing the sample used in Figure Gl.8.4. 

Verification requires sniffing an authentic standard to ensure that the component and the standard have the same retention index and odor quality. 

Determination of retention indices Evaluation of odor quality... 

Comparison of mass spectra, retention indices, odor quality and odor threshold with reference compounds... 

The extract of the volatiles is separated by high resolution gas chromatography (HRGC) and the odor of the compounds is assessed by sniffing the effluent of the GC column in parallel with the FID-detection. This technique allows the detection of odor-active volatiles, the determination of their odor qualities and, most important, the combination of these sensory data with an analytical parameter, the retention index (RI). In Figure 2, the results of... 

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