Volatile compounds classes

Further, the results obtained enabled the correlation of the composition of the volatile fraction of Parmigiano-Reggiano cheese with sensory attributes [42], This subsequent investigation evidences the significance of the flavor in deflning the quality of a food product and, in addition, the contribution of the different volatile compound classes or of the individual substances to the sensory attributes. For example, esters, particularly methyl butanoate, ethyl hexanoate, and isobutyl acetate, are found to be positively related to the fragrant and fruity notes of aged cheese. Short-chain methyl-branched alcohols, secondary products of proteolysis, contribute to a positive maturation component of the aroma, in opposition to the sharp stimuli of free fatty acids (Fig. 6). 

The three classes of terpenes have different temperature profiles. These differences can be related to their boiling points, which are related to their molecular weight and their number of carbons [49]. Monoterpenes are highly volatile compounds (limonene bp763... 

Namiesnik et al. [33] have reviewed the analysis of soils and sediments for organic contaminants. They discuss methods of sample preparation and isolation-preconcentration prior to instrumental determination. Compound classes discussed include volatile organic compounds, polychlorobiphenyls, polyaromatic compounds, pesticides and polychlorodibenzo-p-dioxins and polychlorodibenzofurans. 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

A mammal may emit many volatile compounds. Humans, for instance, give off hundreds of volatiles, many of them chemically identified (Ellin etal., 1974). The volatiles include many classes of compound such as acids (gerbil), ketones, lactones, sulfides (golden hamster), phenolics (beaver, elephant), acetates (mouse), terpenes (elephant), butyrate esters (tamarins), among others. The human samples mentioned before contained hydrocarbons, unsaturated hydrocarbons, alcohols, acids, ketones, aldehydes, esters, nitriles, aromatics, heterocyclics, sulfur compounds, ethers, and halogenated hydrocarbons. Sulfur compounds are found in carnivores, such as foxes, coyotes, or mustelids. The major volatile compound in urine of female coyotes, Canis latrans, is methyl 3-methylhut-3-enyl sulfide, which accounts for at least 50% of all urinary volatiles (Schultz etal, 1988). 

Polycyclic musk fragrances (PMFs) are a major class of compounds. More than 5000 tons of polycyclic musks are synthesized worldwide annually (Kannan et al., 2005). HHCB and AHTN are two of the most frequendy used PMFs worldwide. They are semi-volatile compounds with a log of 5.4—6.3 (Ricking et al., 2003). They am poorly... 

The low thermal stability and the volatility of some of the low molecular weight stationary phases restricted their general use. Therefore, thermally stable and nonvolatile polymeric chiral stationary phases were developed by coupling the diamide phase, via the amino functionality, to a statistical copolymer of dimethylsiloxane and (2-carboxypropyl)methylsiloxane of appropriate viscosity131. The fluid polymeric phase, referred to as Chirasil-Val (Table 2), exhibits excellent properties for the enantiomer separation of a variety of compound classes over a broad temperature range141142. 

The number of volatile compounds collected from white bread by the dynamic headspace method are presented per class in Table II. The values give only a partial impression, because they depend strongly on the conditions used for isolation and detection of volatile compounds. Overall this method seems to release 1/3 of the total number of compounds published for white bread (5). So, the data obtained can only be used for studying differences compared to control samples. 

Volatile compounds are often involved in long distance attraction and are especially important as attractants and repellents (as defined by Kogan, ). One major class of volatile materials, essential oils, is comprised of complex mixtures of terpenes, phenylpropanoid derived compounds and a number of esters, alcohols, aldehydes, ketones, acids, and hydrocarbons. The constituent compounds are mostly of low to medium molecular weight and generally not highly oxygenated. Some of the biological properties of these compounds have been reviewed (17,41,46,55,56). 

Approximately 75 volatile compounds have been identified in juices prepared from plums Prunus domestica) [35]. Lactones from Ce to C12 are the major class of compound in plums [78]. The distribution of plum lactones differs from that found in peaches in that the C12 y-lactones are found in higher concentrations than the corresponding Cio y-lactones and d-decalactone (Fig. 7.2) [78]. GC sniffing has uncovered benzaldehyde, linalool, ethyl nonanoate, methyl cin-namate, y-decalactone and d-decalactone as volatile compounds contributing to plum juice aroma (Table 7.2, Figs. 7.1, 7.2, 7.4, 7.5) [35]. 

The root of parsnip Pastinaca sativa) is eaten boiled or baked. The major classes of compounds identified in raw and cooked parsnip are monoterpenoids, aliphatic sulfur compounds, and 3-alkyl-2-methoxypyrazines [35]. To the best of our knowledge, no investigations have been performed to elucidate the character-impact compounds in parsnip by modern GC-O techniques however, it has been suggested that volatile compounds such as terpinolene, myristicin and 3-sec-butyl-2-methoxypyrazine maybe important contributors to the flavour of parsnip owing to either their high concentrations or their low threshold values, or both [35]. 

Later, the chemical characterisation of the volatiles from yellow passion fruit essence and from the juice of the fruit was done by GC-MS and GC-olfactom-etry (GC-O) [27]. Esters were the components found in the largest concentrations in passion fruit juice and essence extracted with methylene chloride. Analysis by GC-O yielded a total of 66 components which appeared to contribute to the aroma of passion fruit juice and its aqueous essence. Forty-eight compounds were identified in the pulp of Brazilian yellow passion fruits (Passiflora edulis f. flavicarpa) [48]. The predominant volatile compounds belonged to the classes of esters (59%), aldehydes (15%), ketones (11%), and alcohols (6%). 

In another investigation, the volatile compounds were isolated [19] using a Porapack Q trap by vacuum for 2 h and were then eluted with hexane. The esters were the chemical class of compounds that predominated in the samples among 21 volatile compounds detected. Ethyl butanoate, ethyl 2-methylbutano-ate, 1-butanol, ethyl hexanoate, 3-hydroxy-2-butanone, ethyl octanoate, acetic acid, linalool, palmitic acid, and oleic acid were identified in cupuacu pulp by solid-phase extracton [15]. 

A concerted effort was made to develop general methods that could be applied to several substances within the same compound class. This approach was reasonably successful for pesticides, aldehydes, and organolead compounds. The outcome was satisfactory for substances with similar properties however, special treatment was necessary for single compounds within a class that were unusually reactive or volatile. 

The study of the parfait method reported here shows that it does not recover all classes of trace contaminants in water with equal efficiency. Volatile compounds are readily lost in this method. Contamination of eluates during elution of the ion-exchange beds is also a major problem. Even if this contamination were acceptable, the elution of these beds is not complete, as illustrated by the behavior of trimesic acid and glycine. Porous Teflon, on the other hand, offers a means to quantitatively and cleanly recover a set of water contaminants, albeit a set that was not the primary objective of the original parfait method. 

The volatile compounds formed by the Maillard reaction are only one group of flavor compounds in foods. Schutte (1) presents a brief summary of the major classes and their modes of formation from precursors. Some of them can be formed by different pathways. An example is the furans, which can be formed by non-enzymatic browning reaction but also by biotransformation. 

Almost all classes of compounds non-selective Flame ionization detector Non-halogenated volatile compounds (EPA 8015) Phenols (EPA 8041) PAHs (EPA 8100) —All other chemical compounds present in the sample will interfere with the target analytes. —TPH analyses are affected by naturally occurring organic compounds in soils with high humic substance content. 

Analytical methods for the analysis of volatile compounds in the environment have been extensively reviewed.85 87 159 160 The volatility of this class of compounds—industrial solvents, emissions from the petrochemical industry and from combustion engines—suggests that GC should be used for their determination. Solvent-free sample preparation techniques, such as P T (dynamic HS), static HS, and SPME or SBSE, in which the analytes are isolated from the aqueous matrix and simultaneously preconcentrated, are preferred. They also have the advantage that extraction solvents that could interfere with early-eluting, volatile analytes are avoided. If solvent extraction of volatile compounds... 

Heyns et al. (9) have conducted one of the most extensive studies utilizing glucose that was pyrolyzed at 300°C for four hours or at 500°C for three hours under nitrogen. Approximately 130 compounds were observed. They found that the higher pyrolysis temperature resulted in the formation of aromatic hydrocarbons. Other compound classes identified included aliphatic aldehydes and ketones, furans and oxygenated furans, alcohols, lactones, volatile and nonvolatile acids, and oligosaccharides. 

Molasses. A large number of volatile and nonvolatile compounds have been identified in the flavor fractions of various types of molasses (51-621. Compound classes identified include aliphatic and aromatic acids, aldehydes, phenols, lactones, amines, esters, furans, pyrazines, and sulfides. Most of these compounds can arise from carbohydrate degradation through a number of traditional pathways especially because residual nitrogen-containing sources are present. 

Crackers are generally subdivided into three basic categories saltines or soda crackers (also known as cream crackers in the United Kingdom), sprayed crackers, and savory crackers (Hoseney, R.C. Wade, P. Findley, J.W. 1988 Soft wheat products in press). They are a class of baked product with a unique flavor and texture. Crackers are usually made of wheat flower, water, fat, yeast and salt by a process that combines fermentation, baking and dehydration to yield a thin low moisture product. Saltines are the simplest cracker with a typical "cracker-like aroma. This paper reviews the basic flavor chemistry of saltine crackers and presents preliminary data on the extraction of volatile compounds from these crackers. 

Electrospray M+,M++,M+++, etc. ng-pg Non volatile compounds interfaces w/ LC Forms multiply charged ions Limited classes of compounds Little structural information... 

Many materials used for food and beverage packaging have characteristic odors or sensory active compounds (Torri et ah, 2008). The intensity and description of the odor may be affected by the number and type of volatile compounds that are released under environmental conditions at the time of evaluation. Chemical composition of the material and polymer morphology may play a role in the sensory characterization. Sensory descriptors do not define a specific chemical compound but may be related to different compounds, a blend of compounds, and even a limited concentration range of a compound or class of compounds. For example, frans-2-nonenal in water changes in sensory (taste) description from "plastic (0.2 gg/1) to "woody" (0.4-2.0 p.g/1), "fatty" (8-40 pg/1), and "cucumber" (1000 gg/1) (Piringer and Ruter, 2000). Such terms are descriptive of the sensation and perception by human response to the chemical stimuli (Table 2.1). 

Table 10.2. Percentage of major classes of volatile compounds at three stages of maturity.

Method 7 Significant correlations exist between ionic radii in the solid state -or radii of electron orbitals of ions -and the sublimation enthalpies for various compound classes, especially for the halides. It is possible to calculate the standard sublimation enthalpy of transactinide compounds from their calculated ionic radii by making use of a radii-volatility correlation and of corresponding radii of the homologues [44], However, in this procedure it is important to use consistent sets of radii for all homologues, see e.g. Figure 7. 

Chemical vapor transport is used to synthesize thin films of materials on a substrate. The film can be the same composition as the substrate or different. In order to proceed with chemical vapor transport, the constituent elements of the compound to be deposited as a thin film must be brought into the vapor phase. Given that many of the thin films of commercial importance involve elements with little or no practical vapor pressure, a lot of attention has been focused on preparing volatile compounds that contain the elements needed in thin-film preparations. Most chemical supply companies carry these compounds as stock items. The major classes of compounds include metal alkyl, metal carbonyl, metal alkoxide, metal 3-diketonates, and organometallics. Examples of each are given in Table 3.1. 

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