Nontargeted GC-MS approach for volatile profile of toasting in cherry, chestnut, false acacia, and ash wood.

By using a nontargeted GC-MS approach, 153 individual volatile compounds were found in extracts from untoasted, light toasted and medium-toasted cherry, chestnut, false acacia, as well as European and American ash wood, used in cooperage for aging wines, spirits and other beverages. In all wood types, the toasting provoked a progressive increase in carbohydrate derivatives, lactones and lignin constituents, along with a variety of other components, thus increasing the quantitative differences among species with the toasting intensity. The qualitative differences in the volatile profiles allow for identifying woods from cherry (being p-anisylalcohol, p-anisylaldehyde, p-anisylacetone, methyl benzoate and benzyl salicylate detected only in this wood), chestnut (cis and trans whisky lactone) and false acacia (resorcinol, 3,4-dimethoxyphenol, 2,4-dihydroxy benzaldehyde, 2,4-dihydroxyacetophenone, 2,4-dihydroxypropiophenone and 2,4-dihydroxy-3-methoxyacetophenone), but not those from ash, because of the fact that all compounds present in this wood are detected in at least one other. However, the quantitative differences can be clearly used to identify toasted ash wood, with tyrosol being most prominent, but 2-furanmethanol, 3- and 4-ethylcyclotene, α-methylcrotonolactone, solerone, catechol, 3-methylcatechol and 3-hydroxybenzaldehyde as well. Regarding oak wood, its qualitative volatile profile could be enough to distinguish it from cherry and acacia woods, and the quantitative differences from chestnut (vanillyl ethyl ether, isoacetovanillone, butirovanillone, 1-(5-methyl-2-furyl)-2-propanone and 4-hydroxy-5,6-dihydro-(2H)-pyran-2-one) and ash toasted woods.

LC-DAD/ESI-MS/MS study of phenolic compounds in ash (Fraxinus excelsior L. and F. americana L.) heartwood. Effect of toasting intensity at cooperage.

The phenolic composition of heartwood extracts from Fraxinus excelsior L. and F. americana L., both before and after toasting in cooperage, was studied using LC-DAD/ESI-MS/MS. Low-molecular weight (LMW) phenolic compounds, secoiridoids, phenylethanoid glycosides, dilignols and oligolignols compounds were detected, and 48 were identified, or tentatively characterized, on the basis of their retention time, UV/Vis and MS spectra, and MS fragmentation patterns. Some LMW phenolic compounds like protocatechuic acid and aldehyde, hydroxytyrosol and tyrosol, were unlike to those for oak wood, while ellagic and gallic acid were not found. The toasting of wood resulted in a progressive increase in lignin degradation products with regard to toasting intensity. The levels of some of these compounds in medium-toasted ash woods were much higher than those normally detected in toasted oak, highlighting vanillin levels, thus a more pronounced vanilla character can be expected when using toasted ash wood in the aging wines. Moreover, in seasoned wood, we found a great variety of phenolic compounds which had not been found in oak wood, especially oleuropein, ligstroside and olivil, along with verbascoside and isoverbascoside in F. excelsior, and oleoside in F. americana. Toasting mainly provoked their degradation, thus in medium-toasted wood, only four of them were detected. This resulted in a minor differentiation between toasted ash and oak woods. The absence of tannins in ash wood, which are very important in oak wood, is another peculiar characteristic that should be taken into account when considering its use in cooperage.

Polyphenolic profile as a useful tool to identify the wood used in wine aging.

Although oak wood is the main material used in cooperage, other species are being considered as possible sources of wood for the production of wines and their derived products. In this work we have compared the phenolic composition of acacia (Robinia pseudoacacia), chestnut (Castanea sativa), cherry (Prunus avium) and ash (Fraxinus excelsior and F. americana) heartwoods, by using HPLC-DAD/ESI-MS/MS (some of these data have been showed in previous paper), as well as the changes that toasting intensity at cooperage produce in each polyphenolic profile. Before toasting, each wood shows a different and specific polyphenolic profile, with both qualitative and quantitative differences among them. Toasting notably changed these profiles, in general, proportionally to toasting intensity and led to a minor differentiation among species in toasted woods, although we also found phenolic markers in toasted woods. Thus, methyl syringate, benzoic acid, methyl vanillate, p-hydroxybenzoic acid, 3,4,5-trimethylphenol and p-coumaric acid, condensed tannins of the procyanidin type, and the flavonoids naringenin, aromadendrin, isosakuranetin and taxifolin will be a good tool to identify cherry wood. In acacia wood the chemical markers will be the aldehydes gallic and ß-resorcylic and two not fully identified hydroxycinnamic compounds, condensed tannins of the prorobinetin type, and when using untoasted wood, dihydrorobinetin, and in toasted acacia wood, robinetin. In untoasted ash wood, the presence of secoiridoids, phenylethanoid glycosides, or di and oligolignols will be a good tool, especially oleuropein, ligstroside and olivil, together verbascoside and isoverbascoside in F. excelsior, and oleoside in F. americana. In toasted ash wood, tyrosol, syringaresinol, cyclolovil, verbascoside and olivil, could be used to identify the botanical origin. In addition, in ash wood, seasoned and toasted, neither hydrolysable nor condensed tannins were detected. Lastly, in chestnut wood, gallic and ellagic acids and hydrolysable tannins of both the gallotannin and ellagitannin type, can be used as chemical markers.

Polyphenols in red wine aged in acacia (Robinia pseudoacacia) and oak (Quercus petraea) wood barrels.

Polyphenolic composition of two Syrah wines aged during 6 or 12 months in medium toasting acacia and oak 225L barrels was studied by LC-DAD-ESI/MS. A total of 43 nonanthocyanic phenolic compounds were found in all wines, and other 15 compounds only in the wines from acacia barrels. Thus, the nonanthocyanic phenolic profile could be a useful tool to identify the wines aged in acacia barrels. Among all of them the dihydrorobinetin highlights because of its high levels, but also robinetin, 2,4-dihydroxybenzaldehyde, a tetrahydroxydihydroflavonol, fustin, butin, a trihydroxymethoxydihydroflavonol and 2,4-dihydroxybenzoic acid were detected at appreciable levels in wines during aging in acacia barrels, and could be used as phenolic markers for authenticity purposes. Although longer contact time with acacia wood mean higher concentrations of phenolic markers found in wines, the identification of these wines will also be easy after short aging times due the high levels reached by these compounds, even after only 2 months of aging.

Effect of toasting intensity at cooperage on phenolic compounds in acacia (Robinia pseudoacacia) heartwood.

The phenolic composition of heartwood from Robinia pseudoacacia, commonly known as false acacia, before and after toasting in cooperage was studied by HPLC-DAD and HPLC-DAD/ESI-MS/MS. A total of 41 flavonoid and nonflavonoid compounds were identified, some tentatively, and quantified. Seasoned acacia wood showed high concentrations of flavonoid and low levels of nonflavonoid compounds, the main compounds being the dihydroflavonols dihydrorobinetin, fustin, tetrahydroxy, and trihydroxymethoxy dihydroflavonol, the flavonol robinetin, the flavanones robtin and butin, and a leucorobinetinidin, none of which are found in oak wood. The low molecular weight (LMW) phenolic compounds present also differed from those found in oak, since compounds with a ß-resorcylic structure, gallic related compounds, protocatechuic aldehyde, and some hydroxycinnamic compounds are included, but only a little gallic and ellagic acid. Toasting changed the chromatographic profiles of extracts spectacularly. Thus, the toasted acacia wood contributed flavonoids and condensed tannins (prorobinetin type) in inverse proportion to toasting intensity, while LMW phenolic compounds were directly proportional to toasting intensity, except for gallic and ellagic acid and related compounds. Even though toasting reduced differences between oak and acacia, particular characteristics of this wood must be taken into account when considering its use in cooperage: the presence of flavonoids and compounds with ß-resorcylic structure and the absence of hydrolyzable tannins.

Phenolic compounds in chestnut (Castanea sativa Mill.) heartwood. Effect of toasting at cooperage.

The phenolic and tannic composition of heartwood extracts from Castanea sativa Mill., before and after toasting in cooperage, were studied using HPLC-DAD and HPLC-DAD/ESI-MS, and some low molecular weight phenolic compounds and hydrolyzable tannins were found. The low molecular weight phenolic compounds were lignin constituents as the acids gallic, protocatechuic, vanillic, syringic, ferulic, and ellagic, the aldehydes protocatechuic, vanillic, syringic, coniferylic, and sinapic, and the coumarin scopoletin. Their patterns were somewhat different those of oak because oak does not contain compounds such protocatechuic acid and aldehyde and is composed of much lower amounts of gallic acid than chestnut. Vescalagin and castalagin were the main ellagitannins, and acutissimin was tentatively identified for the first time in this wood. Moreover, some gallotannins were tentatively identified, including different isomers of di, tri, tetra, and pentagalloyl glucopyranose, and di and trigalloyl-hexahydroxydiphenoyl glucopyranose, comprising 20 different compounds, as well as some ellagic derivatives such as ellagic acid deoxyhexose, ellagic acid dimer dehydrated, and valoneic acid dilactone. These ellagic derivatives as well as some galloyl and hexahydroxydiphenoyl derivatives were tentatively identified for the first time in this wood. The profile of tannins was therefore different from that of oak wood because oak only contains tannins of the ellagitannins type. Seasoned and toasted chestnut wood showed a very different balance between lignin derivatives and tannins because toasting resulted in the degradation of tannins and the formation of low molecular weight phenolic compounds from lignin degradation. Moreover, the different toasting levels provoked different balances between tannins and lignin constituents because the intensity of lignin and tannin degradation was in relation to the intensity of toasting.

Phenolic compounds in cherry ( Prunus avium ) heartwood with a view to their use in cooperage.

The phenolic and tannic composition of heartwood extracts from Prunus avium , commonly known as cherry tree, before and after toasting in cooperage were studied using HPLC-DAD and HPLC-DAD/ESI-MS. Nonflavonoid (16 compounds) and flavonoid (27 compounds) polyphenols were identified, 12 of them in only a tentative way. The nonflavonoids found were lignin constituents, and their pattern is different compared to oak, since they include compounds such as protocatechuic acid and aldehyde, p-coumaric acid, methyl vanillate, methyl syringate, and benzoic acid, but not ellagic acid, and only a small quantity of gallic acid. In seasoned wood we found a great variety of flavonoid compounds which have not been found in oak wood for cooperage, mainly, in addition to the flavan-3-ols (+)-catechin, a B-type procyanidin dimer, and a B-type procyanidin trimer, the flavanones naringenin, isosakuranetin, and eriodictyol and the flavanonols aromadendrin and taxifolin. Seasoned and toasted cherry wood showed different ratios of flavonoid to nonflavonoid compounds, since toasting results in the degradation of flavonoids, and the formation of nonflavonoids from lignin degradation. On the other hand, the absence of hydrolyzable tannins in cherry wood, which are very important in oak wood, is another particular characteristic of this wood that should be taken into account when considering its use in cooperage.

Volatile compounds in acacia, chestnut, cherry, ash, and oak woods, with a view to their use in cooperage.

Extracts of wood from acacia, European ash, American ash, chestnut, cherry, and three oak species (Quercus pyrenaica, Quercus alba and Quercus petraea) before and after toasting in cooperage were studied by GC-MS. 110 compounds were detected, and 97 of them were identified. In general, all studied woods showed more lignin derivatives than lipid and carbohydrate derivatives, with a higher variety of compounds detected and abundance of them. The toasting led to an increase in the concentrations of most of these compounds, and this increase is especially important in acacia, chestnut and ash woods. The cis and trans isomers of beta-methyl-gamma-octalactone and isobutyrovanillone were only detected in oak wood, 3,4-dimethoxyphenol and 2,4-dihydroxybenzaldehyde only in acacia wood, and p-anisaldehyde and benzylsalicylate only in cherry wood, before and after toasting, and these compounds could be considered chemical markers for each one of these woods. Moreover, each wood has a characteristic volatile composition, from a quantitative point of view, and therefore we can expect a characteristic sensorial profile. The oak wood turned out to be the most balanced, since although it provides a lot of volatile compounds to the aroma and flavor of aged wine, it can do so without masking their primary and secondary aroma. On the whole, toasted acacia and chestnut woods showed a very high richness of studied compounds, as lignin as lipid and carbohydrate derivatives, while cherry and ash were much richer than toasted oak wood in lignin derivatives, but much poorer in lipid and carbohydrate derivatives.