RESUMEN
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 aimat evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.
Asunto(s)
Quercus , Cromatografía de Gases y Espectrometría de Masas , Odorantes/análisis , Olfato , MaderaRESUMEN
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, ß-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.
Asunto(s)
Pinus , Compuestos Orgánicos Volátiles , Cromatografía de Gases y Espectrometría de Masas , Humanos , Monoterpenos , Odorantes/análisis , Olfatometría , Compuestos Orgánicos Volátiles/análisisRESUMEN
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 á .
Asunto(s)
Odorantes/análisis , Quercus/clasificación , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos , OlfatometríaRESUMEN
Four Pinot noir wines from Burgundy were investigated by gas chromatography-olfactometry, with regard to the presence of earthy-smelling compounds. 2-Methylisoborneol (2-MIB) was detected in two of these wines, although the samples were seven years old, contradicting previous reports that this substance is unstable in wine and must. In order to investigate this seemingly paradoxical situation, 2-MIB stability was reinvestigated in wine and in model solution starting with an elevated initial concentration. Although 2-MIB concentration greatly decreased during the 90days of storage, the final concentration measured in both media was well above the odour threshold of the substance. Based on the observation of a decelerating decrease of 2-MIB with time, it was concluded that this substance can still be detected in wine and can induce, in this case, an earthy off-odour on condition that the start concentration is high enough.