The biocatalytic production of flavor naturals that determine chemosensory percepts of foods and beverages is an ever challenging target for academic and industrial research. Advances in chemical trace analysis and post-genomic progress at the chemistry-biology interface revealed odor qualities of nature's chemosensory entities to be defined by odorant-induced olfactory receptor activity patterns. Beyond traditional views, this review and meta-analysis now shows characteristic ratios of only about 3 to 40 genuine key odorants for each food, from a group of about 230 out of circa 10 000 food volatiles. This suggests the foodborn stimulus space has co-evolved with, and roughly match our circa 400 olfactory receptors as best natural agonists. This perspective gives insight into nature's chemical signatures of smell, provides the chemical odor codes of more than 220 food samples, and beyond addresses industrial implications for producing recombinants that fully reconstruct the natural odor signatures for use in flavors and fragrances, fully immersive interactive virtual environments, or humanoid bioelectronic noses.

The recognition of odorants by olfactory receptors represents the first stage in odor discrimination. Here, we report the generation of an expression library containing a large and diverse repertoire of mouse olfactory receptor sequences in the transmembrane II-VII region. From this library, 80 chimeric receptors were tested against 26 odorants after transfection into HEK-293 cells. Three receptors were identified to respond to micromolecular concentrations of carvone, (-) citronellal, and limonene, respectively. We also found that the mouse I7 receptor, unlike the rat I7 receptor, prefers heptanal instead of octanal, as a result of a single valine-to-isoleucine substitution. This finding represents the beginning of a molecular understanding of odorant recognition. The identification, on a large scale, of cognate receptor-odorant interactions should provide insight into olfactory coding mechanisms.

Bitter taste generally causes aversion, which protects humans from ingesting toxic substances. But bitter flavors also contribute to the palatability of food and beverages, thereby influencing nutritional habits in humans. Although many studies have examined bitter taste, the underlying receptor mechanisms remain poorly understood. Anatomical, functional and genetic data from rodents suggest the existence of a family of receptors that are responsive to bitter compounds. Here we report that a human member of this family, TAS2R16, is present in taste receptor cells on the tongue and is activated by bitter beta-glucopyranosides. Responses to these phytonutrients show a similar concentration dependence and desensitization in transfected cells and in experiments assessing taste perception in humans. Bitter compounds consisting of a hydrophobic residue attached to glucose by a beta-glycosidic bond activate TAS2R16. Thus, TAS2R16 links the recognition of a specific chemical structure to the perception of bitter taste. If the ability of TAS2R16 to detect substances with common molecular properties is typical of the bitter receptor family, it may explain how a few receptors permit the perception of numerous bitter substances.