Odors compounds

Flexible multilayer packaging materials obtained by an extrusion coating process are widely used for food, cosmetics or medicines. The low molecular weight compounds formed during processing can impart undesirable odors and tastes to the content of the packaging. The odor- responsible compounds 

Odor compounds may also be released from the plastic materials used in cars. The variety of plastics and possible chemical compounds is broad, which makes the identification of odor causing compounds an extremely comphcated task. An effective and rapid screening of VOCs and semi-VOCs from materials used in automobiles was developed by utihzing the SPME technique [28]. The low molecular weight compoimds extracted from five different automobile materials included different benzene derivatives, aldehydes, esters, biphenyls, phthalates, butylated hydroxytoluene, phenols, alcohols, styrene, triethylene-diamine, carboxylic acids and ketones. A considerable munber of VOCs and semi-VOCs were detected, indicating that more attention should be paid to the selection of materials and additives for automotive parts. 

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Nickel(O) forms a n-complex with three butadiene molecules at low temperature. This complex rearranges spontaneously at 0 °C to afford a bisallylic system, from which a large number of interesting olefins can be obtained. The scheme given below and the example of the synthesis of the odorous compound muscone (R. Baker, 1972, 1974 A.P. Kozikowski, 1976) indicate the variability of such rearrangements (P. Heimbach, 1970). Nowadays many rather complicated cycloolefins are synthesized on a large scale by such reactions and should be kept in mind as possible starting materials, e.g. after ozonolysis. 

Cmde oils from these processes are often of insufficient quaUty to be used directly, particularly for edible products. Impurities such as pigments, phosphatides, volatile odorous compounds, and certain metals must be removed by further processing. 

Many odorous compounds may be converted to compounds with higher odor thresholds or to nonodorous substances. An example of conversion to another compound is the oxidation of H2S, odor threshold 0.5 ppb, to SO2, odor threshold 0.5 ppm. The conversion results in another compound with an odor threshold three orders of magnitude greater than that of the original compound. 

The most common application of carbon adsorption in municipal water treatment is in the removal of taste and odor compounds. Figure 12 provides an example of a process flow diagram for a municipal water treatment plant. In this example water is pumped from the river into a flotation unit, which is used for the removal of suspended solids such as algae and particulate matter. Dissolved air is the injected under pressure into the basin. This action creates microbubbles which become attached to the suspended solids, causing them to float. This results in a layer of suspended solids on the surface of the water, which is removed using a mechanical skimming technique. Go back to Chapter 8 if you need to refresh your memory on air flotation systems. 

In regard to the distribution of the essential oil from one organ of the plant to another, it has been established that there is a circulation of the odorous compounds from the green portions of the plant into the flowers. 

Juttner, F. (1995). Physiology and biochemistry of odorous compounds from fresh-water cyanobacteria and algae. Water Sci. Technol. 31(11) 69-78. 

Jasmonates are important odorant compounds. For the synthesis of new substances of this type, Giersch and Forris developed a domino Claisen/ene/retro-ene process which allows the acid-catalyzed transformation of sorbyl alcohol 4-285 and the cyclic acetals 4-286 into the cycloalkenone 4-292 with the proposed intermediates 4-287 to 4-291 (Scheme 4.61) [97]. A similar domino process had been described by Srikrishna and coworkers [98]. Acyclic acetals gave only the Claisen rearrangement products. 

Possible differences are also well illustrated by 3-thio- and 3-methyl-thiohex-anols and their esters (Table 1). Among these compounds, there is a tendency for the (R) enantiomers to have a typical, fruity aroma. However, for 3-methylthiohexanol (an aroma component of yellow passion fruit) this situation is reversed the (S) enantiomer had the characteristic fruity aroma ( exotisch, fruchtig ).52 For the separation of enantiomers of odorous compounds, enan-tioselective GLC with chiral stationary phases, and MGDC techniques using a conventional capillary column and an enantioselective column are commonly used.53... 

NAPCA (National Air Pollution Control Association). 1969. Air Pollution of Odorous Compounds. NAPCA, Washington, DC. P. 158. 

The concept of mole fraction of a component used in Equation (4.1) is a convenient measure of concentration when dealing with trace quantities and dilute solutions, often experienced in environmental systems. This is especially the case with transport phenomena and equilibrium between phases, where it results in simple quantitative expressions. The phenomena of interest when dealing with the exchange of odorous compounds and oxygen between wastewater and a sewer atmosphere are, in this respect, relevant examples. 

As previously mentioned, the simple equilibrium approach requires that the relevant volatile compounds exist in a nondissociated molecular form in the water phase. For several substances, this is not the case. Hydrogen sulfide is, as an odorous compound, an important example, with sulfide chemical species related according to the following equilibrium ... 

As can be seen from Table 4.1, all three situations are relevant for odorous compounds. Concerning the air-water oxygen transfer (reaeration), resistance primarily exists in the liquid film. 

ODOROUS COMPOUNDS IN SEWER NETWORKS 4.3.1 Occurrence of Odorous Substances in Sewers... 

Only a few studies have been concerned with measurements of specific odorous compounds in sewer systems. Hwang et al. (1995) have analyzed the influent wastewater in a study of malodorous substances in wastewater at different steps of sewage treatment (Table 4.3). 

Although the results in Table 4.3 only represent examples, they are interesting for several reasons. First of all, the table shows that several of the odorous compounds may appear in wastewater from a sewer system in relatively high... 

Release of odorous compounds including hydrogen sulfide from the wastewater into the overlaying atmosphere is a fundamental process for evaluating odor problems. As long as an odorous compound remains in the water phase, odor problems do not exist. 

For sewer systems, three major transport phenomena for odorous compounds may be important ... 

Emission in terms of mass transfer of an odorous compound requires information as shown in Section 4.2. The determination of the overall mass transfer coefficient, KL or K(j [cf. Equations (4.18) and (4.19)] is crucial in this respect. As previously mentioned, KL and Equation (4.18) are typically applied. 

Hwang, Y., T. Matsuo, K. Hanaki, and N. Suzuki (1995), Identification and quantification of sulfur and nitrogen containing odorous compounds in wastewater, Water Res., 29(2), 711-718. Jensen, N.Aa. (1994), Air-water oxygen transfer in gravity sewers, Ph.D. dissertation, Environmental Engineering Laboratory, Aalborg University, Denmark. 

The first three aspects are related to the release of volatile substances into the gas phase of the sewer and from there into the urban atmosphere. These volatile compounds are H2S and organic odorous compounds produced under anaerobic conditions in the wastewater or associated biofilm and sediment. 

Odor evaluation, in perfumes, 18 379 Odor impacts, air pollution dispersion modeling for, 26 725 Odorous compounds controlling, 10 75 in wastewater, 26 723t Odor panels, 26 724 Odor pollution, 26 669 Odor removal, adsorbents for, 1 611 Odors... 

FleldTest (Study the reniowaJ efficiencies of facnratiiefryde, aocbon monoxide, odorous compounds and biological aerosols... 

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