Odor primary

The relationship between molecular stmcture and sensory properties is very unclear for compounds with odor. It seems likely that there is a set of odors that could be called primaries, but a widely accepted Hst of such primary odor quahties has not been devised. Molecular size and shape have been used to... 

Olfactory receptors have been a subject of great interest (9). Much that has been postulated was done by analogy to the sense of sight in which there are a limited number of receptor types and, as a consequence, only three primary colors. Thus attempts have been made to recognize primary odors that can combine to produce all of the odors that can be perceived. Evidence for this includes rough correlations of odors with chemical stmctural types and the existence in some individuals having specific anosmias. Cross-adaptation studies, in which exposure to one odorant temporarily reduces the perception of a chemically related one, also fit into this hypothetical framework. Implicit in this theory is the idea that there is a small number of well-defined odor receptors, so that eventually the shape and charge distribution of a specific receptor can be learned and the kinds of molecular stmctures for a specified odor can be deduced. 

Amoore, J. E., Pelosi, P., and Forrester, L. J. (1977). Specific anosmias to 5a-androst-16-en-3-one and Chemical Senses and Flavour 1,401-425. 

It has been suggested that these anosmias refer to a primary odor classification. These olfactory sensitivity differences could potentially contribute significant differences in flavor perception among individuals for a given product. 

Schieberle, P. 1991. Primary odorants of pale lager beer. Z. Lebensm.-Unters. -Forsch. A 193 558-565. 

In light of this evidence glomeruli can be considered identifiable structures that are focal areas of primary odor processing. Their numbers provide an indication... 

Electronic nose technology relies on the use of solid-state sensors, which can either be chemoresistors, chemodiodes, or electrodes. Primary odors are... 

Table 7-14 Primary Odors for Humans and Compounds Eliciting These Odors...

Schieberle, P. (1991). Primary odorants in popcorn. J. Agric. Food Chem., 39, 1141-1144. 

Amoore, J.E. (1977). Specific anosmia and concept of primary odors. Chem. Senses Flavor, 2, 267-281. 

Anosmia, the inability to smell, can be divided into two classes. General anosmia, the inability to smell any odors at all, usually is the result of disease or accident. More common is specific anosmia, in which an individual either cannot detect a specific chemical substance that most people can detect or displays a threshold of detection for it which is significantly above the normal range. At one time, specific anosmias were finked to the concept of primary odors (13), but confirmation of the combinatorial mechanism of olfaction has put paid to this concept. Interestingly, it has been demonstrated that exposure to the substance can affect anosmia and individuals can begin to smell materials to which they were previously anosmic. This effect has been demonstrated for androstenone, amyl acetate, geranyl nitrile, and isoborneol (14—18). 

Gasser, U., Grosch, W. Primary odorants of chicken broth. Z. Lebensm. Lfnters. Forsch. 1990, 190. 3-8. 

Many microbial metabolites are volatile compounds and in terms of their sensory properties can be broken into two broad categories odorants and tastants (Table 1). Tastants include salty, sour, sweet, and bitter compounds such as amino acids, peptides, and sugars. Primary odorants typically are quite volatile and include carbonyl compounds, esters, and terpenes. There is considerable overlap between the two categories lactones, for example, have both taste and odor properties. In keeping with the theme of this symposium, volatile aroma substances will be the primary focus. 

PRIMARY ODORANTS TASTANTS ODORANTS PRIMARY TASTANTS... 

In this work, we have chosen three substances with a high component of odor intensity for each one of primary odor types, and three of low intensity. In Table 6, selected molecules along with their odor intensities, are listed. As we can see, molecules with comparable odor intensity values need not have structural similarity. This has to be taken into account in any theoretical study about this field. 

Similarity measures had been computed using overlap, Coulomb operators and triple density algorithms. Next, some of the obtained results for each one of the primary odor subsets are presented. 

Anthonomus rubi and Oxyops vitiosa) unpublished data, Gregory S. Wheeler personal communication). Primary odorants marked with bold. E-DMNT 3 -4,8-dimethyl-l,3,7-nonatriene, enantiomers not tested. 

Volatile components of natural and roasted hazelnuts have been investigated by several researchers [7,88,90-98]. Among several volatile aroma-active compounds detected in roasted hazelnut, 5-methyl-( )-2-hepten-4-one (fllbertone) has been reported as the primary odorant (nutty-roasty and hazelnutlike) [88,93,94,96]. Alasalvar et al. [98] studied the comparison of natural and roasted Turkish Tombul hazelnuts and found a total of 39 compounds in natural hazelnut and 79 compounds in roasted hazelnut. These included ketones, aldehydes, alcohols, aromatic hydrocarbons, terpenes, furans, pyrroles, pyrazines, and acids. Pyrazines, pyrroles, terpenes, and acids are detected in roasted hazelnut only. The combination of several volatile aroma-active components that increases upon roasting may contribute to the distinctive and unique flavor of roasted hazelnut. Pyrazines together with ketones, aldehydes, furans, and pyrroles may contribute to the characteristic roasted aroma of hazelnut. Detail information about flavor and volatile compounds in major tree nuts are detailed in Chapter 7. 

As a consequence the minimvun number of monoosmatic components required to encode an odor quality is two. This seems to rule out the concept of primary odors. However, taking into account the relative intensities of the monoosmatic components one could expect that an odor profile with two monoosmatic components of which one dominates decisively would signal an odor queility approaching the simplicity of a primary odor. 

Thus, Amoore suggests that, if we have a specific olfactory receptor for a given odorant then that odorant might be naturally given off by the body. The sweaty odor of isovaleric acid is probably part of the foot odor and is produced by the action of skin bacteria on apocrine secretion (see below). Pyrolline, the spermous odor, has been shown to be produced by enzymatic breakdown of the polyamines in semen (40). Androst-16-en-3-one, the urinous primary odor, has axillary-like odor the related androstenol, which is found in urine, is perceived as a musky odor to some individuals (41). Both steroids are found in axillary sweat and may be formed as metabolites of apocrine secretion. Chemicals which fit the malty anosmia have not as yet been reported from human odor sources. The natural musks, such as cycloheptadecenone (civet), were first obtained from animal scent glands. 

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