Retronasal Habituation: Characterization and Impact on Flavor Perception using Time-Intensity
Pellegrino, R., A. Atchley, S. Ali, J. Shingleton, and C. R. Luckett.  2018.  Chemical Senses, Volume 43, Issue 4, 23 April 2018, Pages e1e136.

Abstract:
Olfactory habituation results from prolonged exposure to an odor, leading to perceptual changes defined by several characteristics. To date, human habituation research has focused on orthonasal olfaction which is perceived externally while ignoring internal routes of odor perception related to flavor. In our study, we conducted two experiments to characterize retronasal olfactory habituation and measured its impact on flavor perception. In Experiment 1, 22 participants rhythmically breathed a food odor (lime), non-food odor (lavender), and blank (propylene glycol) that was presented using an orally-adhered strip, while rating the odor intensity using the time-intensity procedure. After a 10-minute exposure, the participants ate a lime-flavored gummy and rated the lime flavor. In Experiment 2, the same procedure was performed for a low-level lime odor, a simple (lime oil) and complex (lime oil + sucrose + citric acid) beverage as the flavor stimuli. Our results demonstrated two known principles of habituation for retronasally presented odors: 1) prolonged exposure lead to decreased perception, 2) weaker stimuli lead to more rapid habituation. Additionally, we found that the non-food odor habituated slower than the food odor; however, the participants seemed to recover simultaneously upon food and beverage consumption leading to no change in flavor perception.