Olfactory discrimination ability for homologous series of aliphatic ketones and acetic esters.

ABSTRACT

We tested the ability of human subjects to distinguish between members of homologous series of aliphatic ketones (2-butanone to 2-decanone) and acetic esters (ethyl acetate to n-octyl acetate). In a forced-choice triangular test procedure, 20 subjects per series were repeatedly presented with all 21 binary combinations of the seven stimuli and asked to identify the bottle containing the odd stimulus. We found (a) that as a group, the subjects performed significantly above chance level in all tasks but three with the ketones, and all tasks but six with the acetic esters, and thus were clearly able to discriminate between most of the odor pairs presented; (b) marked interindividual differences in discrimination performance, ranging from subjects who were able to significantly distinguish between all 21 odor pairs of a series to subjects who failed to do so with the majority of tasks; and (c) a significant negative correlation between discrimination performance and structural similarity of odorants in terms of differences in carbon chain length for both homologous series. In line with findings of two previous studies using homologous series of aliphatic alcohols, aldehydes, and carboxylic acids, our results suggest that carbon chain length may generally be an important determinant of the interaction between stimulus molecule and receptor, and thus may generally be a molecular property affecting odor quality of aliphatic substances.