Integration of retronasal olfaction and taste: Volatile-enhanced Sweetness

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DESCRIPTION (provided by applicant): This project studies a novel way to create sweet taste that has the potential to reduce consumption of sugars and artificial sweeteners; this novel sweetness is created from odorants. Odorants (volatiles) reach the olfactory receptors by two routes. Sniffing brings odorants from the outside world into the nose where they stimulate the olfactory receptors at the top of the nasal space (orthonasal olfaction). When foods emitting odorants are chewed and swallowed, those odorants are forced up behind the palate and into the nasal space from the back (retronasal olfaction). The brain integrates taste and retronasal olfaction to create flavor. This integration has unusual properties; under some conditions, taste and retronasal olfaction can intensify one another. The food industry has long known that tastes could intensify sensations produced by volatiles (e.g., sugar added to grape juice intensifies the sensation of grape). More recently, chemosensory scientists have learned about the reverse: volatiles can intensity taste, and different volatiles intensify different tastes (e.g., strawberry volatiles enhance sweet; soy sauce volatiles enhance salty). The long-term goal of the proposed research is to understand the perceptual rules underlying volatile-enhanced taste. Volatile-enhanced taste was originally thought to be relatively uncommon, but mathematical analyses of data from tomatoes and strawberries identified more than 30 volatiles contributing to sweetness independently of sugar content. Interestingly, experts in horticulture had already observed that tomato puree "spiked" with certain volatiles tasted sweeter; however, this observation was essentially invisible to the chemosensory community. The present project continues to integrate horticultural and chemosensory science in order to quantify volatile- enhanced sweet. Loss of volatiles after harvest is a serious commercial problem that has led to a rich body of post-harvest science relevant to volatile-enhanced sweetness. Altering volatiles while holding other constituents relatively constant offers experimental techniques to quantify the intensity of the sweetness due to the volatiles. Three sources of volatile alteration will be used in the present project: (1) tomato mutations produce known volatile losses, (2) chilling tomatoes is known to reduce volatiles and (3) exposure to lights of particular wavelengths alters volatiles (sometimes increasing them). Sweetness is typically quantified in food science by scales that can only place items in order of sweetness but the sweetness scales used in this project will allow comparisons of sweetness intensity among items and also comparisons of sweetness perception by different groups (e.g., women and men).