Posterior evaluation of odour intensity in gas chromatography–olfactometry: comparison of methods for calculation of panel intensity and their consequences

Abstract

Four methods of panel intensity calculation were compared for 13 compounds, studied on five concentration levels using gas chromatography-olfactometry. All the methods produced sigmoidal dose-response functions or fractions of sigmoid, when the missing observations were replaced with zero. In contrast, panel intensities calculated only from the reported percepts provided predominantly linear plots. The linearity of such calibration curves can be additionally improved, either by employing a panel of similar dynamic range or by replacing missing observations with predicted (censored) values. Strong scale differences were observed. The panel intensity of methyl benzoate changed rapidly over a very small range of concentrations. Conversely, a very small change of panel intensity was observed for sotolon in a concentration range of three orders of magnitude. Such differences relate closely to the Stevens' slope, in the form of exponential growth function. A systematic decrease of panel intensity was observed for some volatiles at the highest concentration levels. Some of these observations could be explained with the help of current neurobiological knowledge.

Gas chromatography-olfactometry

“…However, the results from the two methods were found to be strongly correlated [23,33,37]. Log-linear and logistic relationships between concentration and posterior odour intensity have been demonstrated [23,48]. Odour intensity responses recorded were also found to correlate reasonably well with odour intensities determined using sensory evaluation [23].…”

“…Many different scale types have been used, including category scales and unstructured line scales. Category scales have ranged from simple three point scales [48] to five point [49] and nine point scales [23,37]. Guichard et al [8] compared a sliding 60 cm scale and a finger span scale.…”

Critical comparison of selected olfactometric methods for the determination of impact odorants. Proposal of a new representation of olfactometric results

“…A last group is constituted of the hybrid methods between DF and intensity methods such as the posterior intensity 8 or VIDEO-Sniff (Vocabulary-Intensity-Duration of Elementary Odours) 9 methods. [10][11][12][13][14][15][16] Parameters like time consumption, panel training and statistical validity of the results were most of the time considered. 3 Comparison of olfactometric methods performance has already given rise to several studies.…”

Identification of odour‐active compounds in dried and roasted nori (Porphyra yezoensis) using a simplified gas chromatography–SNIF technique

“…At the same time, if the intensity was less than 20, the region was assigned as a noise. [8] Using this method, we obtained a composite aromagram based on detection frequencies and total intensities. Based on our criteria, if the detection frequency was no less than 6 and the total intensity was more than 120 (20 Â 6), the aroma event was assigned to be an odour-active event.…”