Sensory analysis sniffing techniques

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. 

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... 

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 (5) of the D.C.I. System and the rotary valve (4) was not switched (analysis using the Desorption - Concentration mode). Thus, 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 measured as similarity or dissimilarity to Black Truffle aroma. 

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). 

GC can be safely and routinely used for essential oils of known composition whose constituents already have been elucidated by hyphenated techniques like GC/MS, GC/FT-IR, NMR, and so on. The use of GC alone for the analysis of new or uncommon essential oils is recommended only for reference information leading to tentative identification of the major constituents. This information also requires support by sensory evaluation. Quantitative determination of the separated constiments must be achieved by GC. Odor evaluation of the eluted components from a GC column is possible through the introduction of a sniffing port fixed to the end of the column via an all-glass splitting device. This allows the analyst to sniff the compound eluted while it simultaneously appears as a peak on the integrator/recorder. 

GC in combination with olfactometric techniques (GC-0) is a valuable method for the selection of aroma-active components from a complex mixture (7). Experiments based on human subjects sniffing GC effluents are described as GC-0. This technique helps to detect potent odorants, without knowing their chemical structures, which might be overlooked by the OAV concept (ratio of concentration to threshold) if the sensory aspect is not considered from the very beginning of the analysis. Experience shows that many key aroma compounds occur at very low concentrations their sensory relevance is due to low odor thresholds. Thus, the peak profile obtained by GC does not necessarily reflect the aroma profile of the food. 

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