Previous studies indicate that the most common result of mixing two odors is the decreased olfactory perception of one or both components in the mixture. An excellent example of this phenomenon is provided by the masking of an unpleasant odor by a pleasant odor. This study hypothesized that dimethyl sulfide (DS; a major chemical component of oral malodor) might be masked by citronellal, a monoterpene aldehyde that produces an intense lemon aroma. To investigate this hypothesis, mice were chosen as odor sensor animals. Mice were trained in a Y maze to discriminate between DS (10 ppm in aqueous solution) and water. A series of generalization tests revealed that these trained "odor sensor" mice could also distinguish between 1 ppm DS and water, but not between 0.1 ppm DS and water. The mice were then confronted with the original choice of 10 ppm DS and water, but now in the presence of various concentrations of citronellal. The mice failed to detect the odor of DS when confronted with 30 ppm citronellal. The mice were similarly confused when confronted with citral (90 ppm) or limonene (3000 ppm). This study is the first to show that citrus odorants can mask the odor of DS, altering the behavioral responses of trained odor sensor mice.
