Hedonic Judgments of Chemical Compounds Are Correlated with Molecular Size

Different psychophysical works have reported that, when a wide range of odors is assessed, the hedonic dimension is the most salient. Hence, pleasantness is the most basic attribute of odor perception. Recent studies suggest that the molecular size of a given odorant is positively correlated with its hedonic character. This correlation was confirmed in the present study, but further basic molecular features affecting pleasantness were identified by means of multiple linear regression for the compounds contained in five chemical sets. For three of them, hedonic judgments are available in the literature. For a further two chemical sets, hedonic scores were estimated from odor character descriptions based on numerical profiles. Generally speaking, fairly similar equations were obtained for the prediction of hedonic judgments in the five chemical sets, with R2 values ranging from 0.46 to 0.71. The results suggest that larger molecules containing oxygen are more likely to be perceived as pleasant, while the opposite applies to carboxylic acids and sulfur compounds

Categorical Dimensions of Human Odor Descriptor Space Revealed by Non-Negative Matrix Factorization

In contrast to most other sensory modalities, the basic perceptual dimensions of olfaction remain unclear. Here, we use non-negative matrix factorization (NMF) – a dimensionality reduction technique – to uncover structure in a panel of odor profiles, with each odor defined as a point in multi-dimensional descriptor space. The properties of NMF are favorable for the analysis of such lexical and perceptual data, and lead to a high-dimensional account of odor space. We further provide evidence that odor dimensions apply categorically. That is, odor space is not occupied homogenously, but rather in a discrete and intrinsically clustered manner. We discuss the potential implications of these results for the neural coding of odors, as well as for developing classifiers on larger datasets that may be useful for predicting perceptual qualities from chemical structures

Chemo-sensory approach for the identification of chemical compounds driving green character in red wines

The present work seeks to define the “green character” of red wines and characterise the groups of molecules potentially involved in that perception. Fifty-four wines were screened by wine experts for different levels of green character. Six different phenolic fractions were obtained by liquid chromatography (LC) and further submitted to sensory and chemical characterisation. The volatile fraction was screened by semipreparative LC, Gas Chromatography-Olfactometry (GC-O) and quantitative analysis. The green character was linked to vegetal aroma, astringency, green and dry tannins according to experts of the Somontano region. Non-volatile fractions containing tannins with mean degree of polymerisation of ten and smaller anthocyanin-derivative pigments (<tetramers) imparted astringency-related sensations such as dryness and stickiness, respectively. No specific aroma compounds were identified in the GC-O study of green wines, however the wines contained significantly higher levels of fusel alcohols. The interaction between isoamyl alcohol and the anthocyanin-derivative fraction and/or tannins is suggested to be involved in the formation of green character in red wines

Correlation between volatile composition and sensory properties in Spanish Albariño wines

To characterize the flavour of Albariño wines, a total of 35 samples representing five geographic areas from Denomination of Origin Rías Baixas were analyzed by sensory descriptive analysis and instrumental analysis (GC-FID). The objective of this work was to study the correlation between instrumental analysis and sensory perception of wine constituents. The results of the investigation were presented by means of multivariate modelling methods such as Principal Component Analysis (PCA) and partial least squares regression (PLSR). Principal Component Analysis showed the distribution of the wines based on chemical and sensory characteristics. The relationships between sensory descriptors and volatile compounds of Albariño wines were studied by Pearson correlation and partial least squares regression (PLSR). The compounds that mostly contributed to the flavour of Albariño wines in instrumental analysis were those related to fruity (ethyl esters and acetates) and floral aromas (monoterpenes). Similar results were found in sensory analysis where the descriptors with the highest Geometric Mean were fruity and floral aromas too (citric, flowers, fruit, ripe fruit, apple and tropical). Therefore, this work demonstrates that some relationships between sensory data and volatile compounds exist to asses sensory properties in Albariño wines.Xunta de Galicia (Spain)

Underlying dimensions in the descriptive space of perfumery odors: part II

NOTICE: this is the author’s version of a work that was accepted for publication in Food Quality and Preference Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Food Quality and Preference, [Volume 43, July 2015, Pages 79–87] DOI 10.1016/j.foodqual.2015.02.018Some comprehensive compilations of odor character descriptions are available in the literature, and they contain valuable information to better understand the underlying dimensions of human odor psychophysics. In the present study, principal component analysis was applied to two olfactory databases of perfumery materials publicly available, which are comprised by those odor descriptors most frequently used in perfumery. The projection of descriptors over the two principal axes (two-component solution) led to related plots, which are also similar to the one obtained in a previous study (Zarzo, 2008). Although the descriptive space of odors is highly multidimensional, our results suggest that it is possible to reach a consensus about how to project perfumery scents on a two-dimensional map, and how to interpret the dimensions of that sensory map. One of them discriminates light vs. heavy odors; the orthogonal axis was correlated with hedonic tones, but it is better interpreted as an underlying latent structure that distinguishes feminine vs. masculine cosmetic scents.Zarzo Castelló, M. (2015). Underlying dimensions in the descriptive space of perfumery odors: part II. Food Quality and Preference. 43:79-87. doi:10.1016/j.foodqual.2015.02.018S79874

Consecutive alcoholic fermentations of white grape musts with yeasts immobilized on grape skins : effect of biocatalyst storage and SO2 concentration on wine characteristics

Abstract Saccharomyces cerevisiae yeasts, immobilized by natural adsorption on grape skins, were used to carry out the alcoholic fermentation step of a winemaking process. The viability of the immobilized cells was evaluated by the implementation of 7 successive fermentations of a white grape must containing 30 mg/L of SO2. The time to complete alcoholic fermentation, the physicochemical characteristics of the produced wines (ethanol, glycerol, organic acids, volatile compounds, color) and sensory properties were evaluated. A traditional fermentation with free cells was used as control. Three other fermentations were conducted after storage of the immobilized biocatalyst (30 d, 4 oC), the first one in the same conditions of the earlier assays, and the other two with higher amounts of SO2 (60 mg/L, 90 mg/L). Wines produced with immobilized cells presented physicochemical and sensory characteristics similar to those traditionally produced with free cells. After three consecutive fermentations, chromatic characteristics became similar to those of traditional wines, but the fermentation time had been reduced from 7 d to 4 d. The fermentative process and the characteristics of the produced wines were not significantly affected by the use of higher amounts of SO2. Immobilized biocatalysts could be stored at least one month without losing its activity.Zlatina Genisheva gratefully acknowledges FCT (Contract/grant number: SFRH/BD/48186/2009) and the Project "BioInd - Biotechnology and Bioengineering for improved Industrial and Agro-Food processes", REF. NORTE-07-0124-FEDER-000028 Co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER, for the financial support of this work

OWidgets: a toolkit to enable smell-based experience design

Interactive technologies are transforming the ways in which people experience, interact and share information. Advances in technology have made it possible to generate real and virtual environments with breath-taking graphics and high-fidelity audio. However, without stimulating the other senses such as touch and smell, and even taste in some cases, such experiences feel hollow and fictitious; they lack realism. One of the main stumbling blocks for progress towards creating truly compelling multisensory experiences is the lack of appropriate tools and guidance for designing beyond audio-visual applications. Here we focus particularly on the sense of smell and how smell-based design can be enabled to create novel user experiences. We present a design toolkit for smell (i.e., OWidgets). The toolkit consists of a graphical user interface and the underlying software framework. The framework uses two main components: a Mapper and Scheduler facilitating the device-independent replication of olfactory experiences. We discuss how our toolkit reduces the complexity of designing with smell and enables a creative exploration based on specific design features. We conclude by reflecting on future directions to extend the toolkit and integrate it into the wider audio-visual ecosystem

Laser clad and HVOF sprayed Stellite 6 coating in chlorine rich environment with KCI at 700 °C

Laser clads and HVOF coatings from a stellite 6 alloy (Co–Cr–W–C alloy) on 304 stainless steel substrates were exposed both bare and with KCl deposits in 500 ppm HCl with 5% O2 for 250 h at 700 C. SEM/EDX and PXRD analyses with Rietveld refinement were used for assessment of the attack and for analysis of the scales. The bare samples suffered from scale spallation and the scale was mostly composed of Cr2O3, CoCr2O4 and CoO, although due to dilution haematite (Fe2O3) was detected in the scale formed on the laser clad sample. A small amount of hydrated HCl was detected in bare samples. While the corrosion of the bare surfaces was limited to comparatively shallow depths and manifested by g and M7C3 carbide formation, the presence of KCl on the surface led to severe Cr depletion from the HVOF coating (to 1 wt%). Both inward and outward diffusion of elements occurred in the HVOF coating resulting in Kirdendall voids at the coating–steel interface. The laser clad sample performed significantly better in conditions of the KCl deposit-induced corrosion. In addition to the oxides, CoCl2 was detected in the HVOF sample and K3CrO4 was detected in the laser clad sample. Thermodynamic calculations and kinetic simulations were carried out to interpret the oxidation and diffusion behaviours of coatings