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Oak wood contains aroma-active compounds that contribute significantly to the chemical structure, olfactory and gustatory qualities of alcoholic beverages and vinegars as by-products that have been either fermented and/or aged in oak barrels. The chemical composition of cooperage oak is highly variable, depending on the degree of toasting and natural seasoning. However, it is unclear whether the odor of oak varies according to different geographical regions and pedoclimatic conditions. Especially in view of the actual challenges in forestry in relation to climate change, the present study aimed at elucidating the odorous constituents of nine natural oak samples from Germany, Austria and Hungary with respect to these influencing parameters. The odor profiles of the oaks were compared, the potent odorants were determined, and selected odorants were quantified using stable isotope dilution assays (SIDA). The majority of the identified odorants in all samples were fatty acid degradation products, followed by a series of odorants with terpenoic structure and others resulting from the degradation of lignin. Several different odorants including 2-propenoic acid and cinnamaldehyde are reported here for the first time in oaks from different growth regions. Odor activity values (OAVs), calculated based on odor thresholds (OTs) in water, revealed hexanal, (E)-2-nonenal, (Z)-3-hexenal, eugenol, vanillin, and whiskey lactone as potent odorants for the oak odor. Principal component analysis of the data obtained from sensory evaluation, comparative aroma extract dilution analysis (cAEDA) and their corresponding quantified odorants showed that the highest separation rate was obtained for Hungarian oak, whereas Austrian and Bavarian oak samples were more similar. Recombination experiments by mixing the dominant odorants in their naturally occurring concentrations revealed a good agreement of the smell properties of the model mixture with the smell of the respective original sample. These findings aim at evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.

The wood of the Cembran pine (Pinus cembra L.), also known as Swiss pine, Arolla pine or Stone pine, has a prominent and long-lasting odor which has been reported to relieve stress in humans. However, the odorants responsible for this are unknown and it is also unclear whether the odor profile depends on the origin of the trees, namely different geographical regions and pedoclimatic conditions. Therefore, in this study human sensory analyses together with isolation and analysis of the target odorants via solvent-assisted flavor evaporation were performed. Afterwards, comparative odor extract dilution analysis (cOEDA) was applied to investigate the odorous constituents of pinewood samples from forests in Austria and Italy. Specific odorants were thereby identified using one-dimensional and two-dimensional gas chromatography-mass spectrometry/olfactometry using two capillary columns with different polarities (DB-5 and DB-FFAP). In total, 103 odorants were detected with successful identification of 98 of these substances. The identified odorants were predominately monoterpenes and sesquiterpenes as well as organic acids. Several compounds including germacrene D, thymol, carvacrol, rotundone, β-caryophyllene, α-humulene, cinnamaldehyde, and ethyl cinnamate are reported here for the first time as odorous constituents of pinewood. Principal component analysis of the data obtained from sensory evaluation and cOEDA indicated that terpenes and sesquiterpenes were correlated with higher hedonic rates for the wood samples. Moreover, a Mantel test between the geographical distances of the trees and their sensory and cOEDA values demonstrated that the origin of the trees had a significant impact on the sensory characteristics of the wood, in agreement with the differences in the relative proportions of different volatile components. As such, the odor of Cembran pinewood is prone to variation but, yet, unique.

The use of suitable fishmeal substitutes for feed in aquaculture is highly desirable to ensure sustainable and economic fish farming. Soybean, linseed, rapeseed, and sunflower seed cakes were investigated as potential fishmeal substitutes. A replacement of 25% (w/w) of the reference fishmeal formulation with oilseed cakes produced pellets with similar nutritional profiles to the reference fish feed but with less pronounced expansion, increased sedimentation velocity, lower water stability and abrasion resistance. The sedimentation velocity of the pellets containing oilseed cakes could be reduced by improving their radial expansion, which was achieved by altering the screw configuration of the extruder, namely by increasing the number of reverse elements and kneading blocks. A reduction in sedimentation velocity could be similarly achieved using finer milled oilseed cake particles. This study indicates that a partial replacement of fishmeal using oilseed press cakes as a by-product from oil-production is feasible. Additionally, the present findings demonstrate that the physical properties of the final fish feed pellets can be modified to be more similar to the fishmeal reference pellets by varying specific parameters in the extrusion process.

Over the centuries, oak wood has been used in the maturation process of alcoholic beverages imparting aroma and flavor notes. Whereas several studies have dealt with the impact of oak wood on the chemical composition of, for example, wine aroma, only limited information is available on the odorant composition of unmodified and raw oak wood itself. To close this gap, a combination of human sensory and chemo-analytical techniques was applied for the elucidation of the chemical composition of oak odor, comprising extraction of the volatile fraction of oak wood by means of solvent-assisted flavor evaporation (SAFE) and subsequent mild concentration of the distillate. Odor extract dilution analysis (OEDA), which is based on gas chromatography-olfactometry (GC-O), was then applied for the targeted characterization of the odor-active compounds. Overall, a total of 97 odorants was identified via gas chromatography-mass spectrometry/olfactometry (GC-MS/O) and heart-cut two-dimensional gas chromatography-mass spectrometry/olfactometry (2D-GC-MS/O). The majority of these odorants comprised a series of terpenes, mainly mono- and sesquiterpenes, aldehydes, acids, and lactones, as well as a number of odorants containing a phenolic core moiety. Several odorants are reported here for the first time as volatile organic compounds in oak wood. Identification of the molecular composition of oak wood odor helps to establish a better understanding of the distinctive smell of oak wood, and offers the basis for unveiling its potential effects on humans when being exposed to oak wood smell in daily life. Graphical abstract ᅟ.

Excretion of odorants and their metabolites into human urine was investigated in urine samples obtained from 14 volunteers after consumption of common dosages of coffee with respect to blank urine samples prior to coffee consumption. Analyses were targeted both on common potent odor constituents of the coffee beverage, as characterized by aroma extract dilution analysis, as well as on volatile constituents of coffee occurring at elevated concentrations and thereby representing quantitatively dominating compounds in the coffee volatile fraction. Identification and quantification of the target substances was accomplished by two-dimensional high resolution gas chromatography mass spectrometry (2D-HR-GC-MS; heart-cut technique) in conjunction with stable isotope dilution assays. Quantification was made on free volatile or odoros marker substances in the urine and their glucuronidated derivatives. Data revealed that some odorants were present at considerably elevated concentrations after the ingestion of coffee. This was confirmed by the odor profiles of the respective urine samples during sensory analysis.

The volatile and odorous profile of human urine may be a rich source for physiological information and could increase our understanding of metabolization and excretion processes of low-molecular weight compounds originating from, for example, dietary or endogenous sources. However, the diagnostic potential of the urinary volatile fraction is not yet fully understood, probably due to the limited application of modern analytical tools in urine volatile analysis. Accordingly, the aim of this study was to evaluate a combined chemo-analytical and human-sensory approach for characterization of the human urine odorant composition. We used one- and two-dimensional high resolution gas chromatography–olfactometry/mass spectrometry to identify commonly occurring and potent odorants in human urine. The studies were carried out on both native urine and on urine that had been treated by glucuronidase assays, with analysis of the liberated odor-active compounds using the same techniques. Based on retention indices, odor qualities and intensities, and mass spectra compared to references, a total of 14 odorants were detected in the majority of the untreated urine samples, and 24 odorants in the glucuronidase-treated samples. A major part of the identified substances are reported here for the first time. Our results show that chemosensory approaches are a useful strategy for the characterization of the odorant profile of human urine.

Odorants elicit physiological effects by direct activation of chemosensory targets in the nose, but may also exert responses after systemic uptake (i.e. after their inhalation, ingestion or dermal penetration). Consequently, the impact of biotransformation processes on odorants and the activation of additional physiological targets by odorants or their biotransformation products can be considerable. The highly diverse physiological effects that can be caused by odorant exposure are reviewed in this chapter. In particular, these are discussed with respect to immediate physiological impacts, such as from the release of odorants and their interaction with the chemosensory system, as well as secondary effects, such as the post-oral or post-inhalation metabolism, distribution and accumulation of odorants and how they affect metabotropic and ionotropic receptors.