GC-sniffing

For estimating the contribution of volatile compounds to bread aroma Rothe and coworkers (S) defined "aroma value" as the ratio of the concentration of some volatile compounds to the taste threshold value of the aroma. This concept was further developed by Weurman and coworkers (9) by introducing "odor value", in which aroma solutions were replaced by synthetic mixtures of volatile compounds in water. These mixtures showed the complexity of the volatile fractions of wheat bread, because none of them resembled the aroma of bread. Recently two variations of GC-sniffing were presented (10-11), in which the aroma extract is stepwise diluted with a solvent until no odor is perceived for each volatile compound separately in the GC effluent. The dilution factors obtained indicate the potency of a compound as a contributor to the total aroma. 

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]. 

There are many samples that can be injected into a gas chromatograph in order to determine what aroma active volatile is present or to quantify a particular one (Maarse and van der Heij, 1994). Unfortunately, many of the protocols that were followed in the past did not rely on meaningful standards or retention indexing, or failed to use GC sniffing or the more formal GC/O procedures to establish that the peaks detected had odor activity however, if the object of the analysis is to simply monitor one or two odorants known to contribute positively or... 

Inject the aroma sample (0.5 pi per solvent extract) in the on-column or splitless mode and simultaneously start the GC sniffing. 

Compare RI indices and aroma quality as assessed during GC sniffing (Acree et al., 1984 Ullrich and Grosch, 1987) with those in the literature (Kondjoyan and Berda-gue, 1996), and the Flavomet (http //www.nysaes.cornell.edu/flavomet). 

Focus identification on the odor-active regions as determined by GC-sniffing and RI values as published in the Flavomet (http //www.nysaes.cornell.edu/flavornet). The fragmentation pattern obtained for the compounds can be compared with those in data banks like the Wiley/NBS Registry of Mass Spectral data (McLafferty and Stauffer, 2000) or the NIST 98 library (National Institute of Science and Technology). 

Chardonnay wines in contact with Hungarian and Russian oak wood with low oak lactone contents scored well for oak wood sensory attributes. GC-sniffing analysis of these woods concluded that such other components as eugenol and the cis and trans isomers of isoeugenol, together with guaiacol and its derivatives, also contributed to the spicy , clove , cinnamon , and woody/oaky aromas. Oak lactones, on the other hand, elicited the odour descriptors sweet , vanilla , and oaky (Dfaz-Maroto et al. 2008). 

Compounds that decreased their odour intensity with oak wood toasting Odour descriptors obtained by GC-sniffing Compounds that increased their odour intensity with oak wood toasting Odour descriptors obtained by GC-Sniffing... 

Debonneville, C., Orsier, B., Flament, I., and Chaintreau, A. (2002). Improved hardware and software for quick gas chromatography-olfactometry using Charm and GC- SNIF analysis. Anal. Chem., 74, 2345-2351. 

Guichard, H., Guichard, E., Langlois, D., Issanchou, S., and Abbott, N. (1995). GC sniffing analysis - olfactive intensity measurement by 2 methods. Z. Lebensm. Unter. Forsch., 201, 344-350. 

Chemical purity and organoleptic purity are not synonymous. For example, the aldehyde (Structure 1) was discovered when a sample of the alcohol (Structure 2) was found to have the expected muguet (lily of the valley) odor (21). The alcohol was prepared from 4-f-amylcyclohexanone (Structure 3) by the scheme shown in Fig. 2. The reduction product contained mostly the desired alcohol (Structure 2) but with some of the isomeric material (Structure 4) in which the double bond had moved into the ring. Flowever, gc-sniffing revealed that neither of these was responsible for the muguet odor of the sample, but rather that it was caused entirely by a tiny trace of aldehyde (Structure 1). Unless organoleptic purity is verified by such techniques, a risk of mistaken attribution of an odor... 

The flavor dilution (FD) factors, 2 , were obtained using the aroma extract dilution method developed by Grosch and co-workers 20. 21). The extract was diluted stepwise with dichloromethane in the volume ratio of 1 1 until odorous compounds were no longer detected by GC sniffing. 

Geosmin was previously found in red beets Beta vulgaris L.) by Murray et al. (1975) and Tyler et al. (1978) and is known as a contaminant of water supplies. A very low aroma threshold of 0.021 ppb is found by Buttery et al. (1976a). By GC-sniffing, Spadone et al. (1990) characterized it as an important contributor to the Rio off-odor, with its earthy-musty odor typical of freshly-ploughed soil. 

Bobillot S., Brevard H., Feria-Morales K. and Mermoud A.F. (1998) GC-sniffing method for identification of coffee aroma profiles. 17th Int. Colloq. Chem. Coffee (Nairobi, 20-25.7.1997) (ASIC, 1998), 214—17. 

Chaintreau A. (2001) Quantitative use of gas chromatography-olfactometry the GC- SNIF method. In Techniques for Analyzing Food Aroma R. Marsili Ed. Marcel Dekker, New York, Second Edition, in press. 

Gc fractions which retained some pepper-like aroma lost this aroma after a few hours, even at low temperatures. Some success was achieved with larger bore glass capillary columns components with odors reminiscent of the pepper aroma partly survived separation in such columns, permitting gc sniffing of the effluent. However, attempts to collect several components were unsuccessful. 

In addition, the various extracts were judged for their smell. They were also investigated organoleptically by carrying out GC-sniffing. 

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