Variation in odor thresholds for l-carvone and cineole and correlations with suprathreshold intensity ratings

Specific anosmias have been reported for l-carvone and cineole, two compounds of importance in food flavor perception. Detection thresholds were assessed in groups of 50+ individuals by ascending forced-choice tests conducted in quadruplicate. Wide individual differences in thresholds were observed. Within the same session, threshold correlations were in the range of +0.8 to +0.9, showing good short-term reliability. Correlations with suprathreshold ratings were moderate (in the range of r = -0.5) after subtraction of false positive ratings for blank samples. However, a cineole mixture experiment failed to show any differences between subgroups that were previously classified as high or low sensitivity on the basis of threshold measurements. Re-testing selected groups after a period of months showed considerable within-individual variation in the thresholds, especially for l-carvone. These results call into question the stability and utility of threshold classification for these two compounds.