Odorous spectra

P americana is one of just a few species of insects in which both peripheral and central olfactory processing have been studied. In contrast to many short-lived lepidopterans, in which the male antenna is highly specialized for sex pheromone reception, the antennae of male cockroaches contain numerous food-responsive sensilla. In addition to olfactory sensilla, the antennae also house mechano-, hygro-and thermoreceptors, as well as contact chemoreceptors (Schaller, 1978 review Boeckh et al., 1984). Extensive ultrastructural and electrophysiological evidence has demonstrated that morphologically defined sensillum types house receptor cells of specific functional types (Sass, 1976, 1978, 1983 Schaller, 1978 Selzer, 1981, 1984 review Boeckh and Ernst, 1987). Boeckh and Ernst (1987) defined 25 types of cell according to their odor spectra, but of the 65 500 chemo- and mechanosensory sensilla on the antenna of adult male P. americana, an estimated 37 000 house cells that respond to periplanone-A and periplanone-B. 

Odor spectrum value OSV. Normalized odor data taken from each peak of the chromatogram that has been adjusted for odor compression using Stephen s Law (Acree, 1997 Ong et al., 1998). The odor chromatogram is redrawn as an odor spectrum. An odor spectrum value can be determined for each odorant in the sample. The values are independent of the method used for collecting odor data and of the concentration, and convey the relative importance of each odorant in the sample. 

The dynamic range of OSME and GC-SNIFF data is generally less than a factor of ten, whereas dilution analysis frequently yields data that cover three or four powers of ten. It has been determined, however, that compressive transforms (log, root 0.5, and so on) of dilution analysis data are needed to produce statistics with normally distributed error (Acree and Barnard, 1994). Odor Spectrum Values (OSVs) were designed to transform dilution analysis data, odor units, or any potency data into normalized values that are comparable from study to study and are appropriate for normal statistics. The OSV is determined from the equation ... 

TABLE 2.1 Average odor spectrum values of the active odorant compound in Amontillado wines.0 Reprinted with permission from Moyano et al. (2010). Copyright 2010. American Chemical Society. 

Figure 2. Odor spectrum gas chromatogram of the "high Brett" wine. GC/MS GCO identification on an OVlOl column of the 15 most potent odor potent compounds.

Comparing the odor spectrum gas chromatograms of the three wines, in Figure 3, a general effect was observed. Floral, fruity compounds were the dominant odorants in the "no Brett" wine while rancid, plastic odors accounted for 1/3 or less of the odor activity in the "medium Brett" wine, the floral, fhiity compounds decrease to 1/2 or less of the odor activity while the rancid, plastic compounds increase to 2/3 in the "high Brett" wine, the rancid, plastic compounds were the dominant odorants while the floral, fhiity compounds were far less dominant. The floral odorant identified as 2-phenyl ethanol was the dominant compound in "no Brett" and "medium Brett" wines in the "high Brett" wine, it was equally as dominant as isovaleric acid and the unknown compound. The fiuity odorant B-damascenone was equally dominant among the three wines for this reason, it should not be considered as a contributor to "Brett" aroma. 

Figure 3. Odor spectrum gas chromatograms on an OVIOI column - the top 15 odor active compounds (a) "no Brett", (b) "medium Brett", (c) "high Brett". Numbers on the chromatogram refer to the chemical structures in figure 4.

IRMS LC MDGC MS MSA NIF NMR OAV OSV PCA RAS RP SDE SFE SIM SNIF SPME TIC TLC Stable Isotope Ratio Mass Spectrometry Liquid Chromatography MultiDimensional Gas Chromatography Mass Spectrometry Multivariate Sensory Analysis Nasal Impact Frequency Nuclear Magnetic Resonance spectroscopy Odor Activity value Odor Spectrum Value Principal Component Analysis Retronasal Stimulation Reversed Phase Simultaneous steam Distillation Extraction Supercritical Fluid Extraction Selected Ion Monitoring Surface of Nasal Impact Frequency Solid Phase Micro Extraction Total Ion Current Thin Layer Chromatography... 

Aroma activities of volatile compounds obtained by GCO dilution analyses were represented as Charm values, and the relative intensities of component odorants were represented in terms of the odor spectrum value (OSV) [14]. Each Charm value was rounded off to two significant figures in order to reflect the actual resolution of the dilution analysis. Acidic, buttery-oily, green-black currant, green-earthy, nutty-roast, phenolic, smoke-roast, soy sauce, sweet-caramel, and sweet-fruity were the aroma descriptions used in all GCO experiments to describe potent odorants. These descriptions were chosen from the results of a single preliminary free choice GCO analysis using a lexicon of words commonly used for coffee evaluation. 

Odor spectrum value (OSV) is the normalized Charm value modified with an approximate Stevens s law exponent ( = 0.5). 

Table 4 Potent Odorants (Above 50% Odor Spectrum Value) Found in the Headspace Volatiles of Roasted Coffee Beans Using the Dynamic Solid-Phase Microextraction Sampling Method...

Figure 8 Two-dimensional scatter plots of the factor loading (A) and principal component score (B) using the total Charm values of 10 aroma descriptions (above 50% OSV). E, Ethiopia T, Tanzania I, Indonesia. Numbers (26, 23, and 18) refer to roast degrees. OSV, odor spectrum value.

To obtain responses closer to the perceived odor intensities, Friedrich and Acree proposed the transformation of the CharmAnalysis or OAV into an odor spectrum using Stevens law (9,10). However, a median value of 0.5 was used as a Stevens exponent, whereas this number may vary significantly from one compound to another [e.g., 0.24 for guaiacol (23)]. 

In a 250 ml Erlenmeyer flask covered with aluminum foil, 14.3 g (0.0381 mole) of 17a-acetoxy-3j5-hydroxypregn-5-en-20-one is mixed with 50 ml of tetra-hydrofuran, 7 ml ca. 0.076 mole) of dihydropyran, and 0.15 g of p-toluene-sulfonic acid monohydrate. The mixture is warmed to 40 + 5° where upon the steroid dissolves rapidly. The mixture is kept for 45 min and 1 ml of tetra-methylguanidine is added to neutralize the catalyst. Water (100 ml) is added and the organic solvent is removed using a rotary vacuum evaporator. The solid is taken up in ether, the solution is washed with water and saturated salt solution, dried over sodium sulfate, and then treated with Darco and filtered. Removal of the solvent followed by drying at 0.2 mm for 1 hr affords 18.4 g (theory is 17.5 g) of solid having an odor of dihydropyran. The infrared spectrum contains no hydroxyl bands and the crude material is not further purified. This compound has not been described in the literature. 

Carvone is an unsaturated ketone responsible for the odor of spearmint. If car-vone has M+ = 150 in its mass spectrum and contains three double bonds and one ring, what is its molecular formula ... 

Our understanding of the physicochemical properties of pyrazines has deepened. The internal rotation and IR spectrum of 2,5-pyrazinedicarboxamide were studied by quantum chemical calculations <05TC73>, and ab initio MO calculations at the MP2/6-31++G( ) level were used to explain the electronic and vibrational properties of complexes of pyrazine and HX linear acids <05JMS2822>. MM and MO calculations were used to investigate the conformational and electronic properties of odor-active pyrazines <05JMS169>, and NMR, IR, X-ray, and DFT methods were used to examine the structures of pyridol l,2-a pyrazinium bromide <05JMS7>. 

Fig. 21.11. Mass spectra of the unknown off-flavor compound after spectral subtraction from the co-eluting peak and the matching spectrum from the NIST library. (Redrawn/redrawn from J. Chromatogr., 351, R.A. Sanders, and T.R. Morsch, Ion profiling approach to detailed mixture comparison. Application to a polypropylene off-odor problem, 525-531, Copyright (1986) with permission from Elsevier.)...

Figure 4. Sensitivity spectrum of the antennal olfactory receptor system in several phytophagous insect species to the green odor components. BAG amplitudes in response to the iruiividual components are visualized in the areas of circles. Data were derived from Refs. 18 (a), 19 (b), 17 (c), and 20 (d).

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