Odor-active Constituents Research Articles

Characterization of the odorous constituents and chemical structure of thermally modified rubberwood

ABSTRACT Rubberwood is a sustainable timber from tropical plantations, and is widely used in human’s daily routine like furniture and interior decoration. The thermal modification technology can effectively make rubberwood preservative, and improve its dimensional stability, while the odorants emitted from thermally modified rubberwood limited its application and recently has attracted people’s attention. In this study, the effects of thermal modification on odor and key odorous constituents of rubberwood were studied. The volatile odorants were identified by sensory evaluation via gas chromatography–mass spectrometry/olfactometry. To gain profound insights into the contribution of single odorants to the overall odor of heat-treated rubberwood, the odor-active constituents were calculated using relative odor activity values (ROAV) on the basis of odor thresholds. It’s revealed that with increasing temperature, the ROAV of 5-methyl-2-furancarboxaldehyde increased from 0.01 to 2.6 and then decreased to 0.7, and 5-methyl-2-furancarboxaldehyde became the important odorant of thermally modified rubberwood ranged from 155°C to 185°C. The odor of 5-methyl-2-furancarboxaldehyde smelled like chocolate and burnt. The identification of odorants from thermally modified rubberwood could provide theoretical guidelines for further controlling the production technology to produce the low odor thermally modified rubberwood.

Comprehensive chocolate aroma characterization in beverages containing jackfruit seed flours and cocoa powder

Jackfruit (Artocarpus heterophyllus Lam) occurs abundantly in Brazil, but its seeds are often underutilized in food nutrition. Previously, we showed that roasted jackfruit seeds are an innovative source of chocolate aroma. In this study, we characterized the volatile content of experimental beverages containing jackfruit seed flours as compared to non-alkaline cocoa powder. The three key results of this study were that (i) the fermented jackfruit seed flour beverage (FJSBev) was similar to the non-alkaline cocoa powder beverage (CTRLBev); (ii) similar volatile groups (acids, alcohols, aldehydes, ester, furans, and pyrazines) were identified in the samples (FJSBev and CTRLBev); (iii) the beverages contained volatile compounds with a low threshold of cocoa attributes (butter, cocoa, coffee, floral, fruit, green, honey, mushroom, nut, and roasted). To conclude, the beverage formulation containing fermented jackfruit seeds had more volatile compounds and odor-active constituents than that with non-alkaline cocoa powder. Collectively, our data demonstrate that fermentation is critical to producing a chocolate aroma. Fermented jackfruit seed flours could be used as a partial or total additive to improve chocolate aroma in food formulations.

Nosy confirmation: reconstitution of the characteristic odor of softwood via quantitative analysis and human sensory evaluation.

The significance of wood odors beyond flavoring effects for barbecues and wine aged in barrels has recently been under discussion. Wood has an immense influence on our physical and mental condition through our palate, such as positive health and mood-stimulating effects. As a result of increased public interest, the key odorants from various natural wood species were recently decoded. To gain profound insights into the contribution of single odorants to the overall scent of distinct wood types, this study compares several softwood species (Scots pine, incense cedar, European larch, Norway spruce, and white fir) by odor profile analysis. Nine odor-active constituents, which were previously detected in those woods, were quantified using stable isotope dilution analysis (SIDA). Odor activity values (OAVs) calculated on the basis of odor thresholds (OTs) determined in cellulose revealed hexanal, octanal, (E)-non-2-enal, p-cresol, vanillin, and thymoquinone as dominant odorants for wood odor. Recombination experiments by mixing the odorants in their naturally occurring concentrations in a cellulose matrix confirmed the successful characterization of the key odorants for Scots pine and incense cedar wood.

Key odorants of industrially-produced Helichrysum italicum subsp. italicum essential oil

To better characterize the constituents responsible for the specific odor of Helichrysum italicum subsp. italicum, the key odorants of a sample of commercial essential oil produced industrially were identified by Gas Chromatography-Olfactometry (Aroma Extract Dilution Analysis) (GC-O AEDA). These compounds were characterized, together with 82 constituents, by careful fractionation procedures and Gas Chromatography-Mass spectrometry and GC-O analyses applied to the entire oil and to its fractions. Several authentic samples of reference constituents (purchased commercially or synthesized by original procedures) were co-injected to confirm some identifications. The most odor-active constituents perceived by all the panelists and showing the highest mean Flavor Dilution factor were 4,6-dimethyloctan-3,5-dione, 1,8-cineole and nerol. Many other constituents in low or, even, in trace amounts, also participate to the global odor of the essential oil.

Characterization of Odorous and Potentially Harmful Substances in Artists' Acrylic Paint.

Acrylic paints are fast drying water based paints that are easy to handle and have a high covering capacity and therefore possess many characteristics that make them applicable in a wide range of applications, such as varnishes or artists paints. Due to their emitted volatile organic compounds, these paints are associated with different work-related diseases and are known to emit an unpleasant odor. In this study six acrylic paints for artists were analyzed regarding their odor-active constituents. Therefore, the samples were extracted with dichloromethane and purified via solvent assisted flavor evaporation prior to analysis of the distillates by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), and GC-GC-MS/O. Additionally all samples were sensorially characterized by a trained sensory panel. The identified odorous substances were primarily benzene derivatives (styrene, ethylbenzene, allylbenzene, propylbenzene) with a plastic-like, aromatic and solvent-like odor. Thereby, polycyclic aromatic hydrocarbons (naphthalene, indane, and tetralin derivatives) contributed to the plastic- and mothball-like odor whereas acrylic monomers (butyl acrylate) were found to be responsible for a mushroom-like and geranium leaf-like odor. As most of these substances are also known to be harmful, a reduction or replacement of these substances by less toxic and non-odor active ingredients is likely to turn out to be advisable in order to reduce the odor and potential negative physiological effects of paints.

Changes in the Key Odorants and Aroma Profiles of Hamlin and Valencia Orange Juices Not from Concentrate (NFC) during Chilled Storage.

Application of the aroma extract dilution analysis (AEDA) on the volatiles isolated by extraction/SAFE distillation from NFC (not from concentrate) juice from Hamlin oranges revealed 51 odor-active constituents in the flavor dilution (FD) factor range of 8 to 8192 among which vanillin, wine lactone, and ( R)-linalool appeared with the highest FD factors. The AEDA applied on the volatile fraction of the same batch of juice stored at 0 °C for 10 months under aseptic conditions showed clear changes in the aroma profile as well as in the FD factors of key odorants. The reduction in the intensity of the citrus-like, pungent, green odor attributes in the aroma profile correlated with the loss of 1-penten-3-one, acetaldehyde, and ( Z)-3-hexenal and a clear decrease in hexanal, octanal, nonanal, decanal, and ( E, E)-2,4-decadienal. Quantitation done by stabile isotope dilution assays followed by a calculation of odor activity values (ratio of concentration to odor thresholds in citrate buffer) confirmed that the quick loss of 1-penten-3-one and acetaldehyde already within a few weeks and a significant reduction in nearly all aldehydes over the storage time of 10 months were responsible for the changes in the overall aroma profile of the juice. The same approach applied on Hamlin juice from the next harvest year as well as on chilled stored NFC juice from Valencia oranges confirmed the results for another harvest year and another orange variety.

Odor-active constituents of Cedrus atlantica wood essential oil

The main odorant constituents of Cedrus atlantica essential oil were characterized by GC-Olfactometry (GC-O), using the Aroma Extract Dilution Analysis (AEDA) methodology with 12 panelists. The two most potent odor-active constituents were vestitenone and 4-acetyl-1-methylcyclohexene. The identification of the odorants was realized by a detailed fractionation of the essential oil by liquid-liquid basic extraction, distillation and column chromatography, followed by the GC-MS and GC-O analyses of some fractions, and the synthesis of some non-commercial reference constituents.

Investigations on the Aroma of Cocoa Pulp ( Theobroma cacao L.) and Its Influence on the Odor of Fermented Cocoa Beans.

The odor-active constituents of cocoa pulp have been analyzed by aroma extract dilution analysis (AEDA) for the first time. Pulps of three different cocoa varieties have been investigated. The variety CCN51 showed low flavor intensities, in terms of flavor dilution (FD) factors, in comparison to varieties FSV41 and UF564, for which floral and fruity notes were detected in higher intensities. To gain first insights on a molecular level of how the cocoa pulp odorants affected the odor quality of cocoa beans during fermentation, quantitative measurements of selected aroma compounds were conducted in pulp and bean at different time points of the fermentation. The results showed significantly higher concentrations of 2-phenylethanol and 3-methylbutyl acetate in pulp than in the bean during the different time steps of the fermentation, whereas the reverse could be observed for the odorants linalool and 2-methoxyphenol. The findings of this study constitute a basis for further investigations on the aroma formation of cocoa during fermentation.

Quantitation of Selected Odor-Active Constituents in Dry Fermented Sausages Prepared with Different Curing Salts

The odor-active compounds of dry-fermented sausages with added nitrite or nitrate as curing agents were identified by gas chromatography-olfactometry (GC-O) applying the detection frequency (DF) method. The quantification of these compounds in the sausage was determined by multiple headspace solid-phase microextraction (multiple HS-SPME). There were no specific odor-active compounds related to the use of nitrite or nitrate although there were differences in the DF value of several compounds. The nitrite-added sausages presented higher DF values for ethanol, 1-hexanol, propanoic acid, 2-heptenal, and nonanal while the nitrate-added sausages had higher DF values for phenylacetaldehyde and 3-methyl-butanal. Eighteen compounds were quantified by multiple HS-SPME. Most of them were above their air detection thresholds, but only hexanal, heptanal, and 1-octen-3-ol were in a concentration higher than their oil threshold values. These compounds would probably be the main contributors to the aroma of fermented sausages.

Identification of the Key Aroma Compounds in Cocoa Powder Based on Molecular Sensory Correlations

Isolation of the volatile fraction from cocoa powder (50 g; 20% fat content) by a careful extraction/distillation process followed by application of an aroma extract dilution analysis revealed 35 odor-active constituents in the flavor dilution (FD) factor range of 8-4096. Among them, 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like), 2- and 3-methylbutanoic acid (sweaty, rancid), dimethyl trisulfide (cooked cabbage), 2-ethyl-3,5-dimethylpyrazine (potato-chip-like), and phenylacetaldehyde (honey-like) showed the highest FD factors. Quantitation of 31 key odorants by means of stable isotope dilution assays, followed by a calculation of their odor activity values (OAVs) (ratio of concentration to odor threshold) revealed OAVs>100 for the five odorants acetic acid (sour), 3-methylbutanal (malty), 3-methylbutanoic acid, phenylacetaldehyde, and 2-methylbutanal (malty). In addition, another 19 aroma compounds showed OAVs>1. To establish their contribution to the overall aroma of the cocoa powder, these 24 compounds were added to a reconstructed cocoa matrix in exactly the same concentrations as they occurred in the cocoa powder. The matrix was prepared from deodorized cocoa powder, which was adjusted to 20% fat content using deodorized cocoa butter. The overall sensory evaluation of this aroma recombinate versus the cocoa powder clearly indicated that the 24 compounds represented the typical sweet, cocoa-like odor of the real sample.

Identification Based on Quantitative Measurements and Aroma Recombination of the Character Impact Odorants in a Bavarian Pilsner-type Beer

Application of aroma extract dilution analysis on the volatiles isolated from a Bavarian Pilsner-type beer revealed 40 odor-active constituents in the flavor dilution (FD) factor range of 16-2048, among which ethyl octanoate, (E)-beta-damascenone, 2- and 3-methylbutanoic acid, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone showed the highest FD factor of 2048. After quantitation of the 26 odorants showing FD factors > or =128 by stable isotope dilution analysis and determination of their odor thresholds in water, odor acitivity values (OAVs) were calculated. The results indicated ethanol, (E)-beta-damascenone, (R)-linalool, acetaldehyde, and ethyl butanoate with the highest OAVs, followed by ethyl 2-methylpropanoate and ethyl 4-methylpentanoate, which was previously unknown in beer. Finally, the overall aroma of the beer could be mimicked for the first time by recombining 22 reference odorants in the same concentrations as they occurred in the beer using ethanol/water as the matrix.

Odor-Active Constituents in Fresh Pineapple (Ananas comosus[L.] Merr.) by Quantitative and Sensory Evaluation

By application of aroma extract dilution analysis (AEDA) to an aroma distillate prepared from fresh pineapple using solvent-assisted flavor evaporation (SAFE), 29 odor-active compounds were detected in the flavor dilution (FD) factor range of 2 to 4,096. Quantitative measurements performed by stable isotope dilution assays (SIDA) and a calculation of odor activity values (OAVs) of 12 selected odorants revealed the following compounds as key odorants in fresh pineapple flavor: 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDF; sweet, pineapple-like, caramel-like), ethyl 2-methylpropanoate (fruity), ethyl 2-methylbutanoate (fruity) followed by methyl 2-methylbutanoate (fruity, apple-like) and 1-(E,Z)-3,5-undecatriene (fresh, pineapple-like). A mixture of these 12 odorants in concentrations equal to those in the fresh pineapple resulted in an odor profile similar to that of the fresh juice. Furthermore, the results of omission tests using the model mixture showed that HDF and ethyl 2-methylbutanoate are character impact odorants in fresh pineapple.