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

We tested the ability of human subjects to distinguish between members of h omologous series of aliphatic ketones (2-butanone to 2-decanone) and acetic esters (ethyl acetate to n-octyl acetate). In a forced-choice triangular t est 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 per formed significantly above chance level in all tasks but three with the ket ones, and all tasks but six with the acetic esters, and thus were clearly a ble to discriminate between most of the odor pairs presented; (b) marked in terindividual differences in discrimination performance, ranging from subje cts 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 an d structural similarity of odorants in terms of differences in carbon chain length for both homologous series. In line with findings of two previous s tudies using homologous series of aliphatic alcohols, aldehydes, and carbox ylic acids, our results suggest that carbon chain length may generally be a n important determinant of the interaction between stimulus molecule and re ceptor, and thus may generally be a molecular property affecting odor quali ty of aliphatic substances. (C) 2001 Elsevier Science B.V. All rights reser ved.