Progress 10/01/03 to 09/30/06
Outputs
Three experiments were completed during the reporting period. They are in press in abstract form, will be presented at the April 2007 meeting of the Association for Chemoreception Sciences (AChemS) and will be published in abstract form in the journal Chemical Senses. First, using high-resolution time-intensity tracking over 50 seconds, we found that times to initial (intensity reaction time) and maximum intensity did not differ for retronasal and orthonasal smelling, but times to final intensity were shorter for retronasal smelling. For both retronasal and orthonasal smelling, initial and final intensity were less than maximum intensity. An unexpected observation was that 1/3 of the subjects tracked intensity up and down during breathing cycles. These data are important because they confirm, using a more precise technique, our previous observation that intensity of smells increases before a decrease occurs. Consequently, design of foods and beverages must include
consideration of this temporal pattern. The difference between those who report a smooth change in intensity and those who report breathing-cycle-locked intensity, which could be revealed only by the type of high-resolution technique that was employed, is interesting, and requires more study. Second, we found that many odorants that are known to be trigeminal stimuli nonetheless cannot be identified if only smelling inside the oral cavity is permitted, The one exception was menthol, the active ingredient in peppermint, which could be identified when restricted to the oral cavity. These observations indicate that if quality-specific trigeminal (chemisthetic) impact in the oral cavity is intended for foods that contain many common trigeminal stimuli, it will be necessary to depend upon non-vapor-phase input. In contrast, for menthol-like odorants, a peppermint perception will regularly begin in the oral cavity. In a third study we found that vapor-phase presentations of several common
fatty acids could not be identified either retronasally or orthonasally. This is important because these common food-components, although volatile, apparently depend for their flavor upon gustatory input. In addition, a chapter on retronasal olfaction is in press in the Encyclopedia of Neuroscience, and the results of two experiments listed in a previous report that has been published in abstract form have now been submitted for publication as full manuscripts. A fourth experiment, examining orthonasal and retronasal interactions, in still underway.
Impacts
It is expected that the designs of foods will be adjusted to take into account our reports on the time-course of odors that originate inside the mouth and the role of oral-cavity-responses in smelling. Our several publications during 2005 on smelling food odors from inside the mouth (retronasal smelling) have lead the scientific community to invite the investigator, B. P. Halpern, to prepare a chapter on differences between retronasal and orthonasal smelling for the journal ChemoSense, and to invite him to present talks on this research at the University of Arizona in Tucson and to the Cornell University Food Science Seminar.
Publications
- Halpern, B.P. 2007. Food and Fragrances: Retronasal olfaction. In: L. Squire, ed., Encyclopedia of Neuroscience, Elsevier. In press.
- Lee, J. and Halpern, B.P. 2007. Time-intensity tracking of retronasal smelling. Chem. Senses (abstract). In press.
- Tamburrino, R.M. and Halpern, B.P. 2007. Identification of air-phase fatty acids: both retronasal and orthonasal failure. Chem. Senses (abstract). In press.
- Parikh, V., Lee-Lim, A.P., and Halpern, B.P. 2007. Retronasal and oral-cavity identification of trigeminal odorants. Chem. Senses (abstract). In press.
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Progress 01/01/05 to 12/31/05
Outputs
Five experiments were completed during the reporting period; four were published in abstract, thesis, or full journal article form. First, we found that, over 60 seconds, adaptation of orthonasal and retronasal smelling were similar, although orthonasal intensity increased before decreasing, while retronasal intensity only decreased over time. This is important because it indicates that retronasal measurements must be made when foods are designed, and that orthonasal measurements are not sufficient. We also saw that matching orthonasal and retronasal intensities by a non-time-intensity procedure did not predict time-intensity intensity. This is a useful technical observation. Secondly, we found that some odorants, for example peppermint, can be both detected and identified when restricted to the oral cavity but that odorants with no trigeminal component can be neither detected nor identified if restricted to the oral cavity. However, the same non-trigeminal odorants
were readily identified when retronasal smelling was permitted. These observations indicate that effects of odorants on the trigeminal system, in addition to olfactory stimulation, must be considered when evaluating odorants. Also, we found that a nose-clip and exhaling through the mouth were sufficient to prevent retronasal smelling. This verifies our own and many previous studies that have used that technique.
Impacts
It is expected that the designs of foods will be adjusted to take into account our reports on the time-course of odors that originate inside the mouth and the role of oral-cavity-responses in smelling. Our several publications during 2005 on smelling food odors from inside the mouth (retronasal smelling) have lead the scientific community to invite the investigator to prepare a chapter on retronasal olfaction for a forthcoming 'New Encyclopedia of Neuroscience'. The development of greater understanding of taste in the human mouth can positively affect development and consumption of foods that can not only satisfy preferred tastes, but can provide nutritional advantages.
Publications
- Halpern, B.P. 2004. When are oral cavity odorants available for retronasal olfaction? In: K. D. Deibler and J. Delwiche, eds., Handbook of Flavor Characterization: Sensory, analysis, Chemistry, and Physiology (pp. 51-63). New York: Marcel Dekker.
- Halpern, B.P. 2004. Retronasal and orthonasal smelling. ChemoSense, 6 (3), 1-7. 2004.
- Shangari, G.K. and Halpern B.P. 2005. Intensity of retronasal and orthonasal odorants: time-intensity tracking. Chem. Senses, 30 (3), 278 (abstract).
- Dragich A.M. and Halpern B.P. 2005. Retronasal smelling: an oral cavity component. Chem. Senses, 30, A202 (abstract).
- Sood S. and Halpern, B.P. 2005. Time and intensity patterns of orthonasal and retronasal smelling. Chem. Senses, 30, A152 (abstract).
- Sood, S. 2005. Comparing Time-Intensity Patterns for Orthonasal and Retronasal Smelling. Honors Thesis, Department of Neurobiology and Behavior, College of Arts and Sciences, Cornell University. Research Advisor: B. P. Halpern.
- Sun, B.C., and Halpern, B.P. 2005. Identification of Air-Phase Retronasal and Orthonasal OdorantPairs. Chem. Senses, 30, 1-14.
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Progress 01/01/04 to 12/31/04
Outputs
Two major studies were completed during the reporting period. A. Retronasal smelling: an oral cavity component. The smell component of flavor from foods inside the mouth is often assumed to be purely olfactory. We thought that part of the odor of foods inside the mouth (retronasal input) might use another sensory system, the trigeminal system. This possibility, that some part of responses to food extracts inside the mouth was due to the trigeminal sensory system rather than the olfactory system, was tested by comparing ability to identify the air phase component of food extracts during normal retronasal smelling (exhaling through the mouth) with ability to identify the air phase component of food extracts when only the oral cavity could be stimulated. We found that peppermint odorant could be identified within the mouth, but other odorants, anise, cinnamon, coffee, orange, and strawberry, could not. This suggested that only odorants that were known to be effective
trigeminal stimuli, such as menthol-containing-peppermint, were likely to provide flavor recognition from stimulation in the mouth. However, sometimes stimuli that we cannot identify can nonetheless contribute to flavor. To test this possibility, we measured the ability to discriminate between the odorants and their solvents. Both peppermint and orange could be discriminated by all subjects. Also, about one-fifth of the subjects could discriminate all the odorants. We conclude that some odorants in the mouth can contribute to flavor in most people separately from input through the olfactory system, and that in a sub-population of people, most odorants have an oral cavity role in flavor, even if they cannot be described. This has important implications both for designing foods and for selecting methods to test foods. B. Time and intensity patterns of orthonasal and retronasal smelling Perceived intensity of odorants delivered by smelling through the nostrils (orthonasal route) or from
inside the mouth (retronasal route) was measured over time. We found that intensity developed more slowly from retronasal compared to orthonasal input, and that, over the first 30 seconds of smelling, there was no consistent loss of smell intensity. These results were important for two reasons. From an applied point of view, the slower development of intensity is relevant because if new or modified foods are tested only using orthonasal input, as is often the case, users' perceptions of the food will not develop at the measured rate when the food or drink is inside the mouth, and consequently the formulations may be incorrect. At a basic science level, there may be differences between orthonasal neural processing, or between odorant access times as a function of flow direction. The absence of intensity loss differs from the usual description that smell intensity decreases over time. It appears that this decrease, which certainly occurs over long periods of time, does not occur with
food-derived odors over 30 seconds. This is important because during eating and drinking, successive sips or bites are separated by less than 30 seconds, and therefore, interactions should be expected.
Impacts
Manufactured foods are designed to provide predictable flavor experiences, and plant and animal varieties are selected for similar outcomes. Knowing that odors in the oral cavity contribute to flavor differently from odors smelled through the nose, develop slowly, and persist for a least 30 seconds, provides valuable guidance in developing foods, or breeding and selecting varieties of plants and animals.
Publications
- No publications reported this period
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