Olfactory discrimination ability for homologous series of aliphatic alcohols and aldehydes

We tested the ability of human subjects to distinguish between members of h omologous series of aliphatic alcohols (ethanol to n-octanol) and aldehydes (n-butanal to n-decanal). In a forced-choice triangular test procedure 20 subjects per series were repeatedly presented with all 21 binary combinatio ns of the seven stimuli and asked to identify the bottle containing the odd stimulus. We found (i) that as a group, the subjects performed significant ly above chance level in all tasks but two with the alcohols and all tasks but four with the aldehydes, and thus were clearly able to discriminate bet ween most of the odor pairs presented; (ii) marked interindividual differen ces in discrimination performance, ranging from subjects who were able to s ignificantly distinguish between all 21 odor pairs of a series to subjects who failed to do so with the majority of tasks; and (iii) a significant neg ative correlation between discrimination performance and structural similar ity of odorants in terms of differences in carbon chain length for both hom ologous series. This suggests that carbon chain length may be one of presum ably several determinants of the interaction between stimulus molecule and receptor, and thus may be a molecular property affecting odor quality of al iphatic alcohols and aldehydes.