Our goal was to determine whether people could learn to discriminate between a five-compound odor mixture with all compounds at the same perceived intensity and that same mixture with any one of the five compounds removed. We first selected, for each panelist separately, concentrations of each of four compounds that were equivalent in intensity to 5 ppm acetylpropionyl. We then constructed, for each participant, a mixture of the five compounds matched in intensity. Panelists then participated in 20 sessions consisting of a series of A-not-A tests with corrective feedback. Panelists, as a group, were able to discriminate between the full five-compound mixture and mixtures with any one of the five compounds removed after 60 trials. However, low d′ values indicated that the mixtures were extremely difficult to discriminate. Only 60% of the panelists were able to discriminate between the complete mixture and the n-1 mixtures even after 200 trials. Practical applications: When compounds are at a similar perceived intensity, using omission testing, as a method for determining the important odorants in a mixture is very likely to indicate that compounds are not important, when, in fact, they are.
Bibliographical noteFunding Information:
The author would like to thank Jean-Paul Schirle-Keller for conducting the chemical analyses of the mixtures. Also thank Aaron Rendahl, Amy Ko, Xuan Wang, and Yi Liu for their help with the statistical analyses. This work was supported by the Sensory Center in the Department of Food Science and Nutrition at the University of Minnesota; and by the Minnesota Agricultural Experiment Station Project MN 18-081.