Discrimination of Complex Odor Mixtures: A Study Using Wine Aroma Models

There are key unanswered questions when it comes to odor mixture discrimination. This study was designed to assess some of those questions regarding configural odor mixture discrimination in humans. We collected data to address the following two questions: 1) What odor features do humans notice when attempting to discriminate between subtly different odor mixtures? 2) Are odor mixtures easier to discriminate when an odorant is added, compared to when a component is removed? Using modern aroma chemistry techniques, an odor mixture resembling a generic white wine was constructed. This wine odor mixture was modified using a series of 3 esters which are commonly found in white wines that vary in chain length and branching. Participants performed a sequence of discrimination tasks for the addition / subtraction of modifiers to the base wine at different concentrations. Only one of the esters (ethyl-propanoate) led to a discriminable odor mixture. As concentration of the modifying odorant was increased, discrimination of odor mixtures was first reported because of changes in odor mixture familiarity and then intensity. We found similar sensitivity odor mixture discrimination regardless of addition or subtraction of modifying compounds, suggesting that perceptual stability of odor mixtures is equally dependent on both imputing missing information (pattern completion) and disregarding extraneous information.