Mixture Perception of rORI7 Agonists with Similar Odors

The straight-chain aldehyde hexanal has a distinct "green-grassy” smell quite different from the similar "citrus-waxy”-smelling homologues heptanal to undecanal (Kittel et al., Chemosens Percept 1:235-241, 2008). Two prior studies demonstrated the absence of cross-adaptation between hexanal and three other homologues (Kurtz et al., Chemosens Percept 3:149-155, 2010) but a significant mixture suppression between the dissimilar-smelling odorants hexanal and octanal (Kurtz et al., Chemosens Percept 4:186-194, 2009). In contrast, this study of similar-smelling octanal and decanal showed little mixture suppression. In contrast to the hexanal and octanal adaptation, data from Kurtz et al. (Chemosens Percept 3:149-155, 2010) showed a significant cross-adaptation between octanal and decanal. The differences observed between mixture suppression and adaptation suggest that these two phenomena are processed separatel

Reference Matching of Dissimilar Binary Odor Mixtures

Hexanal (C6) and octanal (C8) exhibit two different odor qualities at all concentrations: C6 is perceived as green, while C8 is perceived as citrus. This paper examines the odor perception (quality + intensity) of C6-C8 binary mixtures by varying the concentration ratios within the mixtures and using an odor reference-matching task to estimate perceived intensity. Three perceptible concentrations of C6 and C8, low (L), medium (M), and high (H), were prepared. Subjects were trained to match the quality and intensity of blind samples of these standards with their appropriate reference. Mixtures were composed of a focal or "figure” odorant (indicated below in bold) of the same odor quality as the references and a second odorant defined as the "ground” odorant. In subsequent sessions, subjects were asked to evaluate their perception of the quality of the focal odorant in a C6-C8 mixture. Stimuli for C6 matching tasks, where C6 was both the reference and the figure, were: 6L-8M, 6M-8L, 6M-8M, 6M-8H, and 6H-8M. The C8 matching tasks were the same, except that the roles of C6 and C8 were reversed. When the figure odorant was stronger than or iso-intense to the ground odorant, mixtures were often matched to a less intense reference, indicating suppression (compensation) of the figure by the ground odoran

Free-Choice Profiling of OR-I7 Agonists and Homologues Using GCO

Straight chain aldehydes C-7 to C-10 excite olfactory receptor I-7 (OR-I7), while aldehydes C-6, C-11, and C-12 do not. Odorants C-6 to C-12 were analyzed using free-choice profiling to determine differences in olfactory perceptions. A panel of 12 subjects, two male and ten female, analyzed a set of seven saturated straight chain aldehydes of increasing length (C-6 to C-12). Panelists were trained with pure standards and tested in two trials using a seven-odorant probe delivered via gas chromatography-olfactometry. Generalized procrustes analysis of the panelists' scores provided information on differences of perceived odor quality. C-6 was characterized by green and grassy aromas, while C-7 to C-12 were characterized as citrus aromas with additional odor notes varying from floral, fresh, and soapy (C-7) to nutty, oily, and rancid (C-12). Differences in odor quality suggest that several different olfactory receptors including OR-I7 are involved in the processing of aldehydes C-6 to C-1

Taste-Odor Integration in Espresso Coffee

Espresso coffee samples were freshly prepared with 10% sucrose, 0.0143% sucralose (equivalent in sweetness to 10% sucrose), or unsweetened, each with and without nondairy creamer. A sensory panel rated the intensities of "malty,” "caramel,” "roasty,” and "coffee-like.” The concentrations of flavor chemicals associated with the latter three sensations (Furaneol, 2-ethyl-3,5-dimethyl [EDM] pyrazine, and 2-furfuryl thiol, respectively) were determined by gas chromatography, using solid-phase microextraction sampling of coffee headspace. Furaneol and furfuryl thiol were essentially unaffected by creamer addition, but the more nonpolar EDM pyrazine was greatly reduced. The malty, caramel, roasty, and coffee-like flavor intensities were not significantly affected by creamer addition. This appears to be a case of disconnect between the absence of an odorant and perception. Furaneol, furfuryl thiol, and EDM pyrazine concentrations were unaffected by adding either sweetener. The malty sensation was the same with and without added sweetener. The roasty and coffee-like ratings both decreased to similar extents in the samples with the two added sweeteners. The ratings for caramel were considerably increased, again to a similar extent, by both sweeteners. Since the added sweeteners were both nonvolatile, this is clearly a case where taste affected odor perceptio

A Gas Chromatograph-Pedestal Olfactometer (GC-PO) for the Study of Odor Mixtures

Gas chromatography - Olfactometry (GC-O) purifies odorants and delivers them as 1 to 2 second doses to an olfactometer where their odor properties (quale and intensity) can be studied independent of other odors. Adding an odor to the olfactometer air before combining it with the GC effluent creates an odor pedestal upon which an odorant eluting from the GC can be studied to provide insight into mixture perception. This paper describes the development and testing of a gas chromatography - pedestal olfactometer (GC-PO) that produces a Gaussian shaped distribution of one odorant in a background of constant odor composition (the pedestal). A constant pedestal composition was generated by a dynamic headspace released from poly(ethylene) glycol (PEG) solutions into the humidified air of a gas chromatograph-olfactometer (GCO). A magnetic stirrer kept the solvent at the interface in equilibrium with the remainder of the solution producing a constant (+ 10%) pedestal concentration. The resulting pedestal was then combined with a GC effluent and sent to the sniff port of the GC-O. Hexanal, octanal and decanal were analyzed by gas chromatography-mass spectrometry to test the performance and stability of the pedestal. Volatile concentrations of compounds released in the pedestal of GC-PO were linear, constant and could be turned on and off without any detectable background or residual odo

Functional odor classification through a medicinal chemistry approach

Crucial for any hypothesis about odor coding is the classification and prediction of sensory qualities in chemical compounds. The relationship between perceptual quality and molecular structure has occupied olfactory scientists throughout the 20th century, but details of the mechanism remain elusive. Odor molecules are typically organic compounds of low molecular weight that may be aliphatic or aromatic, may be saturated or unsaturated, and may have diverse functional polar groups. However, many molecules conforming to these characteristics are odorless. One approach recently used to solve this problem was to apply machine learning strategies to a large set of odors and human classifiers in an attempt to find common and unique chemical features that would predict a chemical’s odor. We use an alternative method that relies more on the biological responses of olfactory sensory neurons and then applies the principles of medicinal chemistry, a technique widely used in drug discovery. We demonstrate the effectiveness of this strategy through a classification for esters, an important odorant for the creation of flavor in wine. Our findings indicate that computational approaches that do not account for biological responses will be plagued by both false positives and false negatives and fail to provide meaningful mechanistic data. However, the two approaches used in tandem could resolve many of the paradoxes in odor perception

Final Report to the Viticulture Consortium-Eastern Grants Program January 2004: Water and Nitrogen Management to Reduce Atypical Aging of Wine

A report on the use of water and nitrogen management to reduce atypical aging of wine

Impact of Brettanomyces Yeast on Wine Flavor: Sensory Description of Wines with Different

Growth of the yeast Brettanomyces/Dekkera in wine can drastically alter the aroma characteristics to the point where all varietal and regional flavor characteristics are overwhelmed by the flavors produced by these yeasts. To avoid spoilage it is important to know more about the aromas formed by these yeasts and be able to detect the changes in aroma early so that further growth of the yeast and further aroma modification can be avoided. Two groups of commercial wines with suspected "Brett" character were evaluated by two trained panels of judges. The first group included four Cabernet Sauvignon and two Pinot Noir wines; the second included four Cabernet Sauvignon wines. All were evaluated by sensory descriptive analysis and GC/MS 4-ethyl phenol analysis. Characteristic "Brett" aromas such as plastic, burnt plastic, Band-aid (TM), cow manure, barnyard, and horse sweat were summarized by the first group of tasters as 'plastic.' For the second group 'plastic' included only pastic, burnt plastic, and Band-aid (TM) odors. Dry manure and sweaty/animal were separate descriptors. In both groups, the wines were differentiated by univariate analysis of variance (ANOVA) and multivariate discriminant analysis (DA) by two descriptors: plastic and fruity. The greatest fruit character and lowest plastic scores defined the younger Cabernets, and the opposite was true for the older wines. There was little difference between the two Pinot Noirs for either descriptor. The a priori "Brett" observations from the winemakers proved to be a consistent predictor of Brett character for all wines. The observations also agreed with the 4-ethyl phenol concentrations and the post-hoc plastic mean scores from the ANOVA analyses. The "strong Brett" wines were the older vintage wines with higher 4-ethyl phenol concentrations, higher plastic and lower fruity mean scores. Wines with "maybe some" and "no Brett" had the lower 4-ethyl phenol concentrations and more fruit with less plastic scores. This investigation shows that aroma modifications by Brettanomyces yeasts can be reliably detected and quantified with trained tasters. Further investigations into the chemical basis of the 'Brett' aromas will allow us to use chemical indicators to detect activity of these yeasts early