Sniffing technique

A first approach to distinguish between the odor-active compounds and the many odorless volatiles present in such aroma extracts is the application of gas chromatography/olfactometry (GCO, formerly called "sniffing-technique" [13-17]). 

Pollien, P, Ott, A., Montignon, E, Baumgartner, M., Munoz-Box, R., and Chaintreau, A. (1997). Hyphenated headspace Gas chromatography sniffing technique screening of impact odorants and quantitative aromagram comparisons. J. Agric. Food Chem., 45, 2630-2637. 

Sensory values evaluate the olfactive purity through careful trace analysis using sniffing techniques. Determine threshold value, odour value, anosmia. 

In 1966, Le Magnen proposed a designation of the organoleptic qualities of coffee. A choice of tests for the organoleptic valuation of coffee has been presented by Depledt (1968) and a sensory analysis of coffees and instant coffees has also been published by Van Roekel (1976). Vitzthum et al. (1976) were the first to use the sniffing -technique in the analysis of coffee volatiles. 

From the literature mentioned in this chapter, the GC- SNIF technique already exhibits very unique capabilities in terms of quickness and reproducibility and it opens the quantitation field to the GC-O analysis. The superiority of a technique involving a panel instead of one or two assessors is now well established. However, the exact limits are not well known, as they are still under investigation. For instance, it is still unclear in which kind of applications the GC- SNIF or OSME method is more appropriate. As GC-O is the link between chemical and sensorial analyses, it is important to flavor and fragrance research, and improvements in GC-O techniques will continue as the technology evolves and matures. 

F. Drawer and N. Christoph, Significance of the sniffing-technique for the determination of odor thresholds and detection of aroma impacts of trace volatiles. Analysis of Volatiles Methods and Apphcations (P. Schreier, ed.), De Gruyter, Berlin, 1984. J. E. R. Frijters, Some psychophysical notes on the use of the odour unit number. Progress in Flavour Research (D. G. Land and H. E. Nursten, eds.). Applied Science, London, 1979. 

Combined chromatographic-spectroscopic techniques allow complex multicomponent data to be obtained in a single experiment. Essentially, the analysis of monomers, additives, oligomers and polymer can be performed in one step on-line. Postcolumn hyphenation, which comprises spectroscopic detectors, sniffing, fraction collection or heartcutting, is well... 

The extract of the volatiles is separated by high resolution gas chromatography (HRGC) and the odor of the compounds is assessed by sniffing the effluent of the GC column in parallel with the FID-detection. This technique allows the detection of odor-active volatiles, the determination of their odor qualities and, most important, the combination of these sensory data with an analytical parameter, the retention index (RI). In Figure 2, the results of... 

A particular mention is needed for describing one analytical technique capable of detecting the exact site-specific isotope ratio. This technique, called SNIF-NMR (site specific natural isotope fractionating technique), constitutes the most specific and sophisticated method used for food authenticity determination. 

SNIF-NMR and/or IRMS techniques were often combined with trace element analyses (ICP-MS, ICP-OES, FAAS, ETAAS, GFFA) and chemometrics for the geographical characterization of wines. In a relatively old paper, Day et ah (1995) analyzed 165 grape samples collected in 1990 in four different production areas of France (Alsace, Beaujolais, Burgundy, and the Loire Valley). The combined use of isotopic and trace element data allowed an excellent classification of wine samples corresponding to... 

The composition of the volatile fraction of bread depends on the bread ingredients, the conditions of dough fermentation and the baking process. This fraction contributes significantly to the desirable flavors of the crust and the crumb. For this reason, the volatile fraction of different bread types has been studied by several authors. Within the more than 280 compounds that have been identified in the volatile fraction of wheat bread, only a relative small number are responsible for the different notes in the aroma profiles of the crust and the crumb. These compounds can be considered as character impact compounds. Approaches to find out the relevant aroma compounds in bread flavors using model systems and the odor unit concept are emphasized in this review. A new technique denominated "aroma extract dilution analysis" was developed based on the odor unit concept and GC-effluent sniffing. It allows the assessment of the relative importance of the aroma compounds of an extract. The application of this technique to extracts of the crust of both wheat and rye breads and to the crumb of wheat bread is discussed. 

Sensory examination of the effluent from the column of a gas chromatograph by "nasal appraisal" has been introduced into flavor analysis by Fuller et al. (22). Since that time this technique known as "GC-effluent sniffing" has been used in aroma analysis to locate the positions of odorants in a gas chromatogram. It was first... 

The techniques used for the separation of volatiles have been further improved. HPLC and high resolution gas chromatography (HRGC), the latter in combination with effluent sniffing, have been introduced into aroma analysis of bread (25). 

The important odor compounds can be evaluated by the GC-effluent sniffing of a series of dilutions from the original aroma extract. Two variations of this technique were developed by Acree et al. (28, 29) and by us (30-37). 

Sensory Validation of Sampling and GC Techniques. The sensory evaluation was carried out by a panel of three judges (employees of Pebeyre Ltd.). For this study, an external odor port was attached to the gas vent of the D.C.I. system. After the thermal desorption of the volatiles from the trap, the rotary valve was positioned so that the unresolved aroma isolate went to our sniffing port. The response was mesured as similarity or dissimilarity to canned black truffle aroma. 

Site-specific measurement of isotope ratios can be made using site-specific natural isotope fractionation-nuclear magnetic resonance (SNIF-NMR). This was first proposed in 1981 by Martin and Martin [30], who then applied it to the adulteration of food (wine) in 1988 [31]. This technique allows D H ratios for specific H atoms within a molecule to be measured and can provide additional... 

Odor-active components in cheese flavor, many of which are derived from milk lipids, can be detected using GC-olfactometry (GC-O). GC-0 is defined as a collection of techniques that combine olfactometry, or the use of the human nose, as a detector to assess odor activity in a defined air stream post-separation using a GC (Friedich and Acree, 1988). The data generated by GC-0 are evaluated primarily by aroma extract dilution analysis or Charm analysis. Both involve evaluating the odor activity of individual compounds by sniffing the GC outlet of a series of dilutions of the original aroma extract and therefore both methods are based on the odor detection threshold of compounds. The key odourants in dairy products and in various types of cheese have been reviewed by Friedich and Acree (1988) and Curioni and Bosset (2002). 

In a recent study by Landy et al. on odorous substances in paper-based packaging materials, the main volatile substances that caused odour of an offset printed product were identified by olfactometry. In this technique solvent-free extraction using microfibres was successfully applied. The extract was introduced in a gas chromatograph connected to a sniffing port. The odour was then evaluated by a trained assessor. 

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... 

Gas chromatography-olfactometery (GC-O) provides a sensory profile of odor active compounds present in an aroma extract by sniffing the GC effluent. Several techniques have been developed to collect and process GC-O data and to estimate the sensory contribution of individual odor active compounds, including dilution analysis (29, 30), time intensity (31), and detection frequency (32) methods. GC-O has successfully been used to evaluate the odor active compounds of olive oil (33), soybean oil (34), and fish oil enriched mayonnaise (35). 

Volatile solvent abuse or glue sniffing, is common among teenagers, especially males. The success of the modem chemical industry provides easy access to these substances as adhesives, dry cleaners, air fresheners, deodorants, aerosols and other products. Various techniques of administration are employed viscous products may be inhaled from a plastic bag, liquids from a handkerchief or plastic bottle. The immediate euphoriant and excitatory effects are replaced by confusion, hallucinations and delusions as the dose is increased. Chronic abusers, notably of toluene, develop peripheral neuropathy, cerebellar disease and dementia damage to the kidney, liver, heart and limgs also occurs with solvents. Over 50% of deaths from the practice follow cardiac arrhythmia, probably caused by sensitisation of the myocardium to catecholamines and by vagal inhibition... 

G. Remaud (1993) Technical improvements of SNIF-NMR application to mustard oil. In 2" European Symposium Food Authenticity - Isotope Analysis and Other Advanced Analytical Techniques, 20-22 October 1993, Eurofins, Nantes (France)... 

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