Compounds In Oak Wood Research Articles

Identification, quantitation and sensory contribution of new C-glucosidic ellagitannin-derived spirit compounds

Ellagitannins are the main extractible phenolic compounds in oak wood. They can be extracted by eaux-de-vie aging in barrels but rapidly undergo chemical transformations, such as hydrolysis, reduction, oxidation, or even substitution reactions. Given gaps in knowledge about their composition in spirits, the goal of this work was to explore ellagitannin behavior during Cognac eaux-de-vie aging and search for new C-glucosidic ellagitannin-derived compounds. A purification protocol was followed to isolate the new formed compounds. UPLC-UV-Q-ToF and NMR spectroscopy were used to characterize a new C-glucosidic ellagitannin, named brandy tannin B. Two new forms of whiskey tannins were also isolated. The new compound, Brandy tannin B along with β-1-O-ethylvescalagin and β-1-O-ethylvescalin, and whiskey tannins were identified and quantified for the first time in Cognac eaux-de-vie. In addition, the organoleptic impact of brandy tannin B was evaluated. This work brings new insights into ellagitannin composition and their contribution to spirit quality.

Sensory characterisation of Cognac eaux-de-vie aged in barrels subjected to different toasting processes

Toasting is a key step in the barrel-making process. It plays an important role in the breakdown of oak wood compounds and thus influences the chemical composition and organoleptic properties of wines and brandies. However, the effect of toasting on distilled spirit quality has not yet been extensively studied. The objective of this study was therefore to study the impact of toasting on cognac eaux-de-vie by characterising the eaux-de-vie sensorially after 12 months of ageing. Eight eaux-de-vie aged in barrels with 8 different toasts were studied. The 8 toasts represented 4 different temperatures (low, medium, medium plus and high) and two toasting lengths for each temperature (one so-called “normal” and the other “slow”). Sensory analysis was carried out on these eaux-de-vie through several tests. First, a sorting test showed the differences between the samples and then training was carried out on previously chosen descriptors in order to build a sensory profile and perform a ranking test. The study was realised for two alcohol levels: 60 % (v/v), which is the alcohol level of eaux-de-vie in barrels, and 40 % (v/v), which is the alcohol level of a commercial cognac. This approach demonstrated that barrel toasting generally leads to significant sensorial differences in eaux-de-vie during ageing. These differences are greater between a lightly and a highly toasted barrel. This study is a first step in the characterisation of cognac eaux-de-vie aged in barrels made with different toasts.

Validation of a mass spectrometry method to identify and quantify ellagitannins in oak wood and cognac during aging in oak barrels

Ellagitannins are the main extractible phenolic compounds in oak wood; the monomers vescalagin and castalagin, lyxose/xylose-bearing monomers grandinin and roburin E, dimers roburins A and D and lyxose/xylose-bearing dimers roburins B and C are the principal ones. These compounds are responsible for the high durability of wood and may contribute to the organoleptic quality of wines and spirits (color, astringency, bitterness). Despite their importance, their presence and forms in distilled spirits are not well known. The aim of this work was therefore to develop and validate a method to identify and quantify oak wood ellagitannins in Cognac using high liquid chromatography-triple quadrupole (LC-QQQ) analysis. The method was validated using vescalagin as the standard and by studying sensitivity, linearity in working range, intraday repeatability, and intraday precision in order to quantify individual ellagitannins in this complex matrix.

Oak Wood Volatiles Impact on Red Wine Fruity Aroma Perception in Various Matrices.

This research examined the impact of oak wood volatile compounds on the perception of red wine fruity aroma in several matrices. Several aromatic reconstitutions were prepared, consisting of 13 esters, representing the fruity pool of red wine, and 14 oak wood compounds at the various concentrations corresponding to the levels released by light, medium, and heavy toasting of barrels. These reconstitutions were prepared in dilute alcohol solution, dearomatized red wine, and commercial red wine. Sensory analysis revealed the impact of the addition or omission of some oak wood compounds. The "detection threshold" of the fruity pool was then evaluated. The presence of 2-furanmethanethiol individually and the oak wood compound mixture, at concentrations representing various toasting levels, had a significant masking effect on the fruity pool, whereas vanillin had a significant enhancing effect in model solution. Sensory profiles highlighted changes in the perception of fruity nuances in the presence of the oak wood compound mixture. The addition of compounds at concentrations representing different toasting levels led to a predictable increase in the perception of the oak wood descriptors (spicy, smoky, and toasty) in all of the matrices tested. The perception of fruity notes also varied depending upon the toasting level and the complexity of the matrix. In dilute alcohol solution and dearomatized red wine, light toasting preserved or intensified the fruity notes. Generally, in all matrices tested, fresh-fruit and red-berry-fruit notes decreased with the addition of wood at medium and heavy toasting levels.

Identification of odorous compounds in oak wood using odor extract dilution analysis and two-dimensional gas chromatography-mass spectrometry/olfactometry.

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.

Oak barrel tannin and toasting temperature: Effects on red wine condensed tannin chemistry

Red wine is known to derive specific aromas and to have its color enhanced by oak wood compounds, but the effect of oak barrels on wine tannin chemistry is not well known. Cabernet Sauvignon wines were aged from 8 to 12 months in oak barrels made with three different ellagitannin levels (Tannin Potential, TP) and two toasting levels. Condensed tannin composition, activity and ellagitannin contents have been characterized using HPLC-DAD and protein precipitation. Red wines aged in high TP barrels contained more ellagitannins, condensed tannins with lower mass and lower pigmented tannins percentage than in low TP barrels. Red wines aged in high-temperature toasted barrels contained less ellagitannins, condensed tannins with higher mass and higher pigmented tannins percentage than in low-temperature toasted barrels. Combined effects of ellagitannin, toasting levels and aging have been identified. The selection of barrels for ellagitannin content and toasting temperature can be used to manage red wine development.

Contribution of oak lignans to wine taste: chemical identification, sensory characterization and quantification

The modification of wine taste during oak ageing is due to the release of non-volatile compounds from wood. Among these molecules, some lignans have been previously described as exhibiting bitterness. However, the lack of knowledge concerning this class of compounds in oak wood led us to explore both their structural diversity and their sensory properties. Nine lignans were isolated from extracts of Quercus petraea oak heartwood. Among them, one new compound called quercoresinol was identified and four other molecules were described for the first time in Quercus genus. The presence of these lignans in oaked wine was then established and their gustatory properties were evaluated. Lyoniresinol was the bitterest compound with a detection threshold of 1.5 mg/L. An LC–HRMS quantitative method was performed to study the influence of oenological practices on lyoniresinol concentration in wine.

Contribution of oak wood ageing to the sweet perception of dry wines

Background and Aims Winemakers observe a sensory effect of oak ageing in wines, but the phenomenon has never been fully described. The aim of this study was to determine the influence of the ageing container on the sweetness of dry wines and to evaluate the contribution of oak volatile compounds. Methods and Results Both white and red dry wines were produced in various containers, such as stainless steel and oak tanks, and new and used oak barrels. Sensory analysis (with or without use of nose clip) by a panel of experts showed an increase in sweetness when wine was in contact with wood. Oak volatile compounds (vanillin, β-methyl-γ-octalactone and eugenol) were quantified by gas chromatography-mass spectrometry and then added to the wines to obtain the same concentration in all samples. To determine the contribution of the volatiles to the increase in sweetness, the treatments were tasted again after such an ‘oak aroma’ homogenisation. The ranking of the wines remained unchanged. Conclusion These results demonstrate that the sweet perception of dry wines depends on the nature of the ageing container, and that these oak volatiles are not involved in this phenomenon. Significance of the Study This work confirms an empirical observation and establishes for the first time the sweetening effect of oak ageing, strongly suggesting the existence of sweet non-volatile compounds in oak wood.

Interaction of Œnococcus œni and oak wood compounds

The purpose of this work was to study the effect of wood extract on Œnococcus œni growth in synthetic media and its influence on the concentration of volatile compounds when lactic acid bacteria (LAB) are present. Analytical results and sensorial consequences are described when malolactic fermentation was performed in tank or barrels. Using gas chromatography-mass spectrometry, the modifications in oaklactone, eugenol, isoeugenol and vanillin levels were monitored in the presence of Œ. œni. These volatile compounds are known to have powerful characteristic odors (woody, spicy, smoky and vanillin) and to play a role in wine aroma. LAB cultures were performed in synthetic media supplemented with oak wood shavings or extracts. The bacterial growth rate was lower in the absence of heated shavings. This study shows that LAB, especially Œ. œni, are able to interact with wood and form volatile compounds. In laboratory medium, the heating of wood favored bacterial viability more than the simple addition of wood shavings. This is the first demonstration of the capacity of wine Œ. œni to enhance volatile compounds from wood.

Effect of oak barrel type on the volatile composition of wine: Storage time optimization

When it comes to deciding about the length of time for ageing wine in barrels it is necessary to take into account several factors such as wine composition and characteristics of barrels. Adapting wood to wine is not an easy matter. Ageing duration is highly variable depending on a wine's origin, type and quality. The aim of this study is to investigate the behaviour of new barrels and once-used barrels depending on the ageing period of wine. From the results obtained it can be seen that for ageing wine during a short period (6–9 months), there was quite a big difference in the concentration of most of the oak wood compounds between wine aged in new barrels and wine aged in once-used barrels. However, due to the chemical or biochemical transformations of certain compounds from oak wood in wine over time, their concentration in long-term ageing (12–15 months) was similar for both wine aged in new barrels and in once-used barrels. The compounds which became more exhausted from barrel use were, furanic aldehydes, phenolic alcohols, phenolic aldehydes, and oak-lactones.

Characterization of carotenoids and their degradation products in oak wood. Incidence on the flavour of wood

The presence of carotenoids (principally β-carotene and lutein) in oak wood is an important factor when selecting wood for barrel making. Amounts are generally small and vary considerably between samples, depending on several parameters and notably the colour of the piece of wood. Among the samples studied, pinkish oak woods were significantly richer in carotenoids than other coloured woods. Carotenoids are highly sensitive to oxygen, light and temperature, producing many degradation products, mostly norisoprenoids. A new method is suggested in order to extract and identify these oak wood compounds. Norisoprenoids are new aromatic compounds, some of which have fruity and floral notes, which can contribute to the fruity character of the aromatic range of oak. To cite this article: M.-F. Nonier et al., C. R. Chimie 7 (2004) .

Extraction of wood compounds by use of subcritical fluids

A study of the extraction of oak wood compounds with subcritical water-ethanol mixtures as extractants, with an ethanol content between 0 and 60%, is reported. Identification and characterization of the extracted compounds were achieved by spectrophotometry and by gas chromatography with either flame ionization or mass spectrometric detection. Extraction was performed statically by use of a single cycle or repeated cycles. All variables affecting the extraction process were studied and optimized. Extraction time and temperature were 60 min and 200°C, respectively. Comparison of the extract thus obtained with commercial extracts showed the former to be rich in compounds characteristic of the commercial extracts. The method also enables manipulation of extract composition by changing the temperature and the water/ethanol ratio used. It is faster than traditional procedures for obtaining wood extracts.

Chemical and sensory changes in white wines fermented in the presence of oak chips

Summary Three samples of French oak and one sample of American oak were analyzed by different gas chromatographic‐mass spectrometric (GC/MS) methods. Two methods of quantifying the main volatile compounds in oak wood were compared, namely, Direct Thermal Desorption coupled with GC/MS and analysis of mixtures of water‐ethanol and wines that had been in contact with oak chips by extraction using an organic solvent followed by GC/MS analysis of the extract. The ratio of the two oak lactones released into the wine by the oak chips was the same as the ratio observed in original, untreated wood. These substances are of particular sensory importance in wines aged in oak wood barrels. Thus, the use of oak chips in white wines may be advantageous. The wines steeped with the oak chips improved their acceptability rating 2 points on a scale of 9.

Gas chromatographic-mass spectrometric analysis of volatile compounds in oak wood used for ageing of wines and spirits

Characterization of French oak samples used in the ageing of wines and spirits can be achieved by determination of the composition of their volatile fraction. Soxhlet extraction and simultaneous extraction-distillation have been used to obtain different voltatile fractions. analysis of these fractions by gas chromatography-mass spectrometry enables tentative identification of up to ninety six components including phenols, furans, terpenes, acids, esters, and lactones. The results obtained depend on the method and solvent used.

Quantitative analysis of the principal volatile compounds in oak wood by direct thermal desorption (DTD) and GC/MS

This work proposes one method of quantifying the principal volatile compounds in oak wood using the direct thermal desorption (DTD) technique coupled with GC/MS. These compounds have a particular sensory importance in wines aged in oak wood barrels: furfural, trans and cis-β-methyl-y-octalactones, eugenol, vanillin and syringaldehyde. The described method requires practically no sample handling and is precise and sensitive.