Odor components

Aroma chemicals are isolates, or chemically treated oils or components of oils. Some components are removed physically, others chemically. In most cases, they are further purified by distillation. For example, Bois de Rose (rosewood) oil may be distilled to isolate linalool, which may be then further treated chemically to yield derivatives such as linalyl acetate, an important fragrance ingredient and a primary component in its own right of lavender and lavandin oils. Vetiver oil Haiti, although containing only 70% alcohols, is treated with acetic anhydride, then carefully distilled to include valuable odor components in the distillate, even though they may not be esters. 

OT,-methionine propane odorant natural gas odorant components water repeUants prevulcanization inhibitor flocculent... 

When it comes to indoor air quality, interaction of people with their gaseous surroundings is the most important factor. In rooms with poor air exchange, the presence of people causes a steady deterioration in air quality. Air quality may be understood here and henceforth as a numeric measurement for the content of unhealthy and odorous components (air comfort). Additionally, building materials... 

Equation (4.20) expresses that the total resistance to mass transfer across the air-water boundary is equal to the sum of the resistances across the liquid film and the gas film. The importance of the magnitude of Henry s constant is, in this respect, evident. For high values of HA, e.g., exemplified by 02, the resistance mainly exists in the water film, and turbulence in a sewer will, therefore, enhance the water-air transfer process. The importance of turbulence in the water phase is reduced for odorous components with a relatively low HA value, and turbulence in the air phase will correspondingly increase the release rate (Table 4.1). As seen from Equations (4.20) and (4.21), these facts also depend on the k1A/k2A ratio that varies according to system characteristics. 

The release of odorous components (i.e., the water-air mass transfer aspects) is dealt with in Chapter 4, and the behavior of sulfur (hydrogen sulfide) was, in this respect, exemplified. Figure 4.4 gives not just an understanding of the release phenomena but also an overall view of the pathways and sinks of sulfur components under sewer conditions. 

Ackman R, Hingley J, MacKay K (1972) Dimethyl sulfide as an odor component in Nova Scotia fall mackerel. J Fish Res Bd Can 29 1085-1088... 

A third ICIPE study focuses on identifying tsetse repellents. Field biologists recognized long ago that tsetse flies bite some wild animals but not others. We now know that flies shun such animals as waterbucks, elands, and zebras, because the odors of these mammals contain fly repellents. This discovery precipitated a search for odor components that deter tsetse and led eventually... 

A method is proposed to assess the Odom Potential of slurries and sludges by sampling in the liquid phase, followed by extraction of odorous components under reproducible conditions. The approach has inherent advantages in providing speedy and less costly information for the prediction of odour nuisance, scheduling land disposal, and for comparing methods of sludge treatment and stabilisation. 

BARTH, C.L., HILL, D.T. POLKOWSKI, L.B. (1974). Correlating odor intensity index and odorous components in stored dairy manure. Transaction of the American Society of Agricultural Engineers 17 (4), 742-744. 

The response of vertebrates to olfactory stimulation is affected by previous experience but behaviour can be specifically affected by odours (pheromones) (4). The olfactory system has been shown to detect specific components within complex mixtures and analytical chemistry techniques have been used to identify these active components (5). We have assessed the application of these methods to the problems of agricultural odours in an attempt to develop techniques applicable to both slurries and air samples. The identification of the odorous components might allow specific treatment methods to be developed. In addition, the designation of a range of indicator compounds might be useful in practice for monitoring abatement of odour nuisances. 

SPOELSTRA, S.F. (1980) Origin of objectionable odorous components in piggery wastes and the possibility of applying indicator components for studying odour development. Agriculture and Environment, 5(3), 241-260. 

Another experiment used cod liver oil, crude krill extract, and the krill odor components trimethylamine and pyrazine, with phenylethanol (rose odor) as control. Several procellariiform species were attracted to krill extract. The krill odor components attracted giant petrels, cape petrels, blue petrels, Antarctic petrels, Kerguelen petrels, and black-browed albatrosses. Cape petrels were more attracted to trimethylamine than to pyrazine and cod liver oil hut blue petrels responded most to cod liver oil (Nevitt, 1999). 

The short-tailed fmit bat, Carollia perspicillata, discriminates the odor of ripe from that of green bananas. Odor cocktails of banana odor components were distinguished from the whole odor of banana (Laska, 1990). The two most common esters of banana odor are isopentyl acetate and isobutyl acetate. Nearly all fruit odors contain ethyl acetate. Isopropyl acetate and 2-pentanone are characteristic of putrefying fruits. 

Motion pictures still lack the odor dimension. Experimental scent movies are improving. The Science City in Paris features a small theater that screens films with an odor component. Scent cans on a carousel rotate in position, get activated, and an air stream blows odors toward the viewer at the appropriate scene. A more recent computer-controlled mixing apparatus can provide many more odor combinations. 

Laska, M. (1990). Olfectory sensitivity to food odor components in the short-tail fruit bat,... 

Three 3-alkyl-2-methoxypyrazines (24b, 24c, and 24d) are detected as odor components in the monarch butterfly, Danaus plexippus (Table III). The wide variability in pyrazine content observed with this insect is correlated with similar variability in the larval food plants, Asclepias sp. It seems possible that the pyrazines may be one of the factors implicated in the food choice mechanism (69). 

The aposematic beetle, Metriorrhynchus rhipidius, contains three pyrazines as warning odor components and two amides as bitter principles (Tables III, V, and VIII) (97). Of the three components with the beetlelike odor, the most characteristic is 2-methoxy-3-isopropylpyrazine (24b). The other two components are 2-methoxy-3-methylpyrazine (24a) and 2-methoxy-3-sec-butylpyrazine (24d). It would seem likely that these compounds will occur in the defensive systems of the aposematic beetles. The two amide components, detectable in the hemo-lymph exuded by adult beetles, are 3-phenylpropanamide (130) and l-methyl-2-quinolone (57), the latter being the major component. It seems likely that these bitter principles contribute to distastefulness to potential predators. 

Many cyclic sesquiterpene alcohols are key odor components in essential oils, for example, cedrol in cedarwood oil, the vetiverols in vetiver oil, and the santalols in sandalwood oil. Since these alcohols have not yet been synthesized on an industrial scale, they are described under the oil in which they occur (Chapter 3). Some of their derivatives, however, are discussed in this section. 

Diallyl disulfide [2179-57-9] is an essential odor component of garlic oil [233]. 

The major constituents of common caraway oil are (+)-limonene and (+)-car-vone, which together may make up more than 95% of the oil. (+)-Carvone is the essential odor component. 

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).

Figure 7. Intensity of neural activity in 23 olfactory receptor cells in the antenna of the Colorado beetle, in response to tTins-2-hexen-I-ol (t-2-H-I-ol), cis-3-hexen-I-ol (c-3-H-I-ol), and Uins-2-hexenal (t-2-H-al). The increase of neural activity in response to individual green odor components is visualized in the areas of circles...

Investigations in our laboratories have been concerned with characterizing odor components produced by irradiating approximately 15-pound batches of ground, raw, lean beef, vacuum-packed in sardine cans and enzyme-inactivated 4). Irradiation at 5 megarads was carried out either in the M.I.T. cobalt-60 source before removing volatile constituents by distillation, or concurrent radiation-distillation at 5 megarads was carried out by procedures described elsewhere 15,17). 

Table V. Relative Proportions Of Possible Indispensable Off-Odor Components in Nonirradiated and Irradiated Beef...

The epoxidation of dehydrolinalyl acetate 35 provides the corresponding epoxide 36 (75 %) which can lead to karahanaenone 38, a key odorous component of hop oil621. The epoxide 36 can be converted to the keto acetate 37 (82%) by an electrogenerated acid (EG Acid)-catalyzed rearrangement. Hydrogenation followed by alkaline hydrolysis of 37 gives 6-hydroxy-2,6-dimethyl-7-octen-3-one (86%) and subsequent thermal dehydration at 200 °C affords 38 (Scheme 3-12). 

At first glance, labeled-line coding of olfactory signals may seem in contrast to the ensemble or across-fiber code (Shepherd, 1985) where complex mixtures of odorants or even individual odorant components are perceived as patterns of activity across an ensemble of neurons and AL glomeruli. However, recent experiments examining odor coding of individual ORNs in Drosophila and mammalian olfactory systems demonstrate that individual ORNs are capable of a wide spectrum of responses. In the fly, a particular odor can excite one neuron while inhibiting another, and a particular neuron can be excited by one odor and... 

Flavour is a complex sensation, made up principally of smell and taste, but touch and hearing contribute as well. The human senses of smell and taste differ in sensitivity, between each other and depending on the nature of the component eliciting the sensation. Substances may have no impact at all (such as oxygen or carbon monoxide) or exhibit very low thresholds (such as 2 X 10 14g mL 1 water for the odour of bis-2-methyl-3-furyl disulfide).204 In general, odour thresholds are much lower than taste thresholds and so flavour tends to be dominated by odorous components, by substances able to reach the olfactory epithelium high up in the nose, that is, substances with at least some volatility. Hence, the emphasis on the volatile compounds derived from the Maillard reaction. 

Some plant volatiles, however, are highly specific and composed of compounds not found in unrelated plant species.46 Allyl isothiocyanate, a specific odor component, is a breakdown product of glucosinolates in oilseed rape, B. napus. This compound attracts the crucifer flea beetle, Phyttotreta cruciferae, which is consistently found feeding in oilseed rape or canola fields.50... 

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