Changes in low molecular weight phenolic compounds in Spanish, French, and American oak woods during natural seasoning and toasting

The evolution of low molecular weight polyphenols in Spanish oak heartwood of Quercus robur,Quercus petraea, Quercus pyrenaica, and Quercus faginea was studied by HPLC, in relation to the processing of wood in barrel cooperage. The polyphenolic composition of Spanish woods subjected to natural seasoning for 3 years and to the toasting process was studied in relation to those of French oak of Q. robur (Limousin) and Q. petraea (Allier) and American oak of Q. alba (Missouri), which are habitually used in cooperage. The concentrations of benzoic and cinnamic acids and aldehydes of Spanish woods increased during seasoning depending on the duration of this process and in the same way as those of French and American woods. The process having the main influence on the phenolic composition of wood was the toasting. It led to high increases in the concentration of phenolic aldehydes and acids, especially cinnamic aldehydes (sinapic and coniferylic aldehydes), followed by benzoic aldehydes (syringaldehyde and vanillin) and benzoic acids (syringic and vanillic acids). This polyphenolic composition in Spanish oak species evolved during toasting as in French and American oak, but quantitative differences were found, which were especially important in American species with respect to the others.     

Chemical characterization of oak heartwood from Spanish forests of Quercus pyrenaica (Wild.). Ellagitannins, low molecular weight phenolic, and volatile compounds

The need for new sources of quality wood supply for cooperage has led to looking into the possibility of utilizing Quercus pyrenaica Wild. oak, a species native to the Iberian peninsula, as an alternative to other European (Quercus robur and Qurecus petraea) and American (Quercus alba) oaks. The low molecular weight phenolic composition, ellagitannins, and volatile compounds (including a wide range of compound families such as volatile phenols, furanic compounds, lactones, phenyl ketones, other lignin-derived compounds, and volatile compounds related to off-flavors) of green heartwood from Spanish forest regions were studied by HPLC and GC, in order to know its enological characteristics. The chemical composition of Q. pyrenaica is similar to that of other species commonly used in cooperage to make barrels, showing only quantitative differences that were more significant with respect to American than to French species. The four provenance regions studied showed similar chemical composition, with high variability among individuals, often higher than the variability among regions of provenance, but in line with that described in other European and American oak woods. Therefore, this species must be considered to be suitable for aging wine.     

Evolution of ellagitannins in Spanish, French, and American oak woods during natural seasoning and toasting

The evolution of tannins in Spanish oak heartwood of Quercus robur L., Quercus petraea Liebl.,Quercus pyrenaica Wild., and Quercus faginea Lam. was studied in relation to the processing of wood in barrel cooperage. Their evolution was compared with that of French oak of Q. robur (Limousin, France) and Q. petraea (Allier, France) and American oak of Quercus alba L. (Missouri), which are habitually used in cooperage. Two stages of process were researched: the seasoning of woods during 3 years in natural conditions and toasting. Total phenol and total ellagitannin contents and optical density at 420 nm of wood extracts were determined. The ellagitannins roburins A-E, grandinin, vescalagin, and castalagin were identified and quantified by HPLC, and the molecular weight distribution of ellagitannins was calculated by GPC. During the seasoning process the different ellagitannin concentrations decreased according to the duration of this process and in the same way as those in French and American woods. The toasting process also had an important influence on the ellagitannin composition of wood. Roburins A-E, grandinin, vescalagin, and castalagin decreased during this process in the Spanish wood species, in the same proportion as in the French and American ones. Also, the seasoning and toasting processes lead to qualitative variations in the structure of ellagitannins, especially in the molecular weight distribution, as was evidenced by GPC analysis of their acetylated derivatives.     

Volatile compounds in a spanish red wine aged in barrels made of Spanish, French, and American oak wood

A red Rioja wine was aged in barrels made of Spanish oak wood (Quercus robur, Quercus petraea,Quercus pyrenaica, and Quercus faginea) during 21 months. The concentrations of some volatile compounds [syringaldehyde, vanillin, eugenol, maltol, guaiacol, 4-ethylphenol, cis and trans isomers of beta-methyl-gamma-octalactone, 2-furfuraldehyde, 5-methyl-2-furfuraldehyde, 5-(hydroxymethyl)-2-furfuraldehyde, and furfuryl alcohol] were studied in these wines and compared with those of the same wine aged in barrels made from French oak of Q. robur (Limousin, France) and Q. petraea (Allier, France) and American oak of Quercus alba (Missouri). Similar concentrations of these compounds were found in wines aged in Spanish and French oak wood barrels, and significantly different concentrations were found with respect to wines aged in barrels made of American oak wood, indicating a different behavior. Thus, wines with different characteristics were obtained, depending on the kind of wood. Also, the kind of wood had an important influence on sensory characteristics of wine during the aging process. Spanish oak wood from Q. robur, Q. petraea, and Q. pyrenaica can be considered to be suitable for barrel production for quality wines, because a wine aged in barrels made of these Spanish oak woods showed similar and intermediate characteristics to those of the same wine aged in French and American oak woods usually used in cooperage.     

Effect of the seasoning method on the chemical composition of oak heartwood to cooperage

The effect of various oak wood seasoning methods, natural seasoning in open air, artificial seasoning in a kiln, and a mixed method that combines open air and kiln drying, on the chemical composition in American ( Quercus alba) and French ( Quercus petraea) oak was studied. The results confirm the evolution of ellagitannins in wood, low molecular polyphenols, and volatile compounds in relation to oak species and seasoning method. Natural seasoning in open air can be considered a superior method to mixed or artificial drying for wood seasoning in cooperage. It was more effective in reducing the excess of ellagitannins, especially in French oak wood. Moreover, the evolution of wood volatile compounds was more positive in the natural seasoning than mixed or artificial drying, since it led to woods with higher aromatic potential (larger concentrations of compounds such as volatile phenols, phenolic aldehydes, furanic compounds, and cis- and trans-beta-methyl-gamma-octalactones) than mixed or artificial methods. However, the three seasoning methods showed similar effectiveness regarding the desired reduction of off-flavors compounds.     

Characterization of volatiles in extracts from oak chips obtained by accelerated solvent extraction (ASE)

Sixteen commercially available oak chips, differing in origin (French or American) and toasting level, were extracted by an accelerated solvent extraction method and characterized by their volatile composition. About 80 compounds were identified and quantified, a great part of them from the thermodegradation of lignin and cellulose. One furanone (solerone) and two C-13 norisoprenoids (3-oxo-alpha-ionol and a 3-oxoretro-alpha-ionol isomer) were also tentatively identified and reported for the first time in toasted wood. Quantitative data demonstrated the oak chips to be not so different from the composition of light- or medium-toasted wood barrels, which was reported by other authors. The same data suggest that toasting level had the strongest influence on the volatile composition of chip samples. Phenyl ketones, volatile phenols, and some furanic compounds were the most influenced. On the other hand, the influence of wood origin was found to be weaker.     

Extractives content in cooperage oak wood during natural seasoning and toasting; influence of tree species,geographic location,and single-tree effects

The chemical composition of cooperage oak wood is highly variable, depending upon the tree species (Quercus robur L. versus Quercus petraea Liebl.), its geographic location, and the single-tree effect. In the process of cask-making, natural seasoning and toasting contribute strongly to the modification of the oak wood chemical composition and therefore influence wine cooperaging. HPLC and GC quantification of ellagitannins and volatile compounds such as whiskey-lactones, eugenol, and vanillin over a sample set of 61 pedunculate oaks and 72 sessile oaks originating from six different forests showed that natural drying leads to a decrease of the ellagitannins and total extractives content level and a quasi constant level of the volatile compounds. Toasting (medium type) drastically enhanced the loss of ellagitannins and the gain in volatile compounds. Statistical treatment showed that the species effect remained significant throughout the process of drying and toasting, but not the provenance. The poor correlation with ring width of extractives levels measured on fresh timber remained unchanged as did the single-tree effect, with high variability found for all chemical parameters. These results provide further evidence that cooperage oak selection should not be based solely on the wood grain or the provenance but rather on a species-provenance combination.     

Influence of geographical origin and botanical species on the content of extractives in American, French, and East European oak woods

The chemical composition of East European (Republic of Moldova, Ukraine, and Romania) oaks was investigated profoundly for the first time in the present study and compared with American and French counterparts. Taking into account the high natural variability of oak extractives contents, the wide-ranging sampling was performed for all oak origins: 276 French oaks, 102 East European oaks of both species (Quercus robur L. and Quercus petraea Liebl.), and 56 American oaks (Quercus alba). These oaks were compared with great attention paid to the extractives, which are most important for sensorial impact in wine or spirit maturation, such as ellagitannins and principal odorant substances (aromatic aldehydes, lactones and phenols). The substances in question were studied by application of HPLC and GC-MS techniques. The pattern of all studied extractive contents allowed adequate separation of oak samples according to their geographical origin or botanical species. The highest separation rate was for American and French oaks, whereas East European samples could be partially misclassified in two sets mentioned above. The most important variables for species discrimination were whiskey lactone related variables and ellagitannins, whereas the most important features for distinguishing the origin were eugenol, 2-phenylethanol, vanillin, and syringaldehyde. These substances allowed the distinction of French and East European woods of the same species. With regard to chemical composition, East European wood held the intermediary place between American and French oaks according to their ellagitannin and whiskey lactone levels; nevertheless, it was characterized by specific high values of eugenol, aromatic aldehydes, and 2-phenylethanol.     

Volatile compounds and sensorial characterization of wines from four Spanish denominations of origin, aged in Spanish Rebollo (Quercus pyrenaica Willd.) oak wood barrels

The evolution of almost 40 oak-related volatile compounds and the sensorial characteristics of red wines from four Spanish denominations of origin (DOs) (Bierzo, Toro, Ribera de Duero, and Rioja) during aging in barrels made of Rebollo oak wood, Quercus pyrenaica, were studied and compared to the same wines aged in American and French oak barrels. Each oak wood added unique and special characteristics to the wine, and in addition, each wine showed a different ability to extract the compounds, which result in these characteristics from the oak wood. In general, wines aged in Q. pyrenaica wood were characterized by high levels of eugenol, guaiacol, and other volatile phenols. In regards to compounds like cis-whiskylactone or maltol, the behavior of this wood is very similar to that of American oaks. When considering phenolic aldehydes and ketones, the levels of these compounds are intermediate between those of French and American woods and depend greatly on the type of wine. The type of oak, on the other hand, does not affect the chromatic characteristics of the wines. In sensory analysis, the biggest differences are found in the olfactory phase. Among the four DOs studied, wine aged in Q. pyrenaica presented the highest notes of wood, with more aromas of roasting, toasting, milky coffee, spices, or wine-wood interactions. The wines aged in barrels made of Q. pyrenaica wood were highly regarded, and preference was shown for them over those same wines when they had been aged in barrels of American or French oak.     

Influence of the species and geographical location on volatile composition of Spanish oak wood (Quercus petraea Liebl. and Quercus robur L.)

The influence of the species and geographical origin on the volatile composition of wood samples from 80 Spanish oaks (55 Quercus petraea Liebl. and 25 Quercus robur L.) has been studied. Oak volatile components were isolated by simultaneous distillation-extraction and analyzed by gas chromatography-mass spectrometry. cis- and trans-beta-methyl-gamma-octalactones were the main constituents, the cis stereoisomer being predominant. Other important volatile components were furfural, 5-methylfurfural, guaiacol, eugenol, vanillin, or syringaldehyde. The main differences were established between species, Quercus petraea being significantly richer in volatile compounds than Quercus robur; however, the variability found among trees was high. Differences among geographical provenances were much less important than those found between species.     

Evolution of phenolic compounds of spanish oak wood during natural seasoning. First results

Low molecular weight polyphenols and ellagitannins were analyzed by HPLC, and the molecular weight distribution of ellagitannins was calculated by GPC, in oak heartwood of Quercus robur L., Quercus petraea Liebl., Quercus pyrenaica Wild., and Quercus faginea Lam., grown in Spain, before and after 1 year of seasoning, in Bordeaux, France. During this process, the concentrations of low molecular weight polyphenols (acids and aldehydes, benzoic and cinnamic, and coumarins) increased, and those of ellagitannins (castalagin, vescalagin, and roburins A-E) decreased. A similar behavior for the A and B compounds in all species was not found. This modification in the chemical composition was similar in the four Spanish species of Quercus studied and allowed the differentiation between the unseasoned wood and the wood after the first year of seasoning.     

Influence of distillation system, oak wood type, and aging time on composition of cider brandy in phenolic and furanic compounds

A control of phenolic and furanic compounds in cider brandy was carried out during maturation in oak casks, studying three technological factors: distillation (rectification column vs double distillation), oak wood type (French vs American), and aging time (32 months). Gallic acid and benzoic and cinnamic aldehydes significantly increased during maturation of cider brandies, the highest level of these phenolics being obtained when aging was conducted in French oak casks. Benzoic acids increased during aging, though furanic compounds were not influenced by the time factor. Distillation and wood factors significantly influenced furanic concentration; 5-hydroxymethylfurfural not was detected in fresh spirits and was extracted in the highest proportion in French oak. Volatile furanics, such as 5-methylfurfural, furfural, and 2-furylmethyl ketone, were influenced by the distillation factor, with the use of the double distillation system producing a higher level of these compounds. Scopoletin was the majority coumarin detected in cider brandies, the highest yield of which was obtained with the use of American oak.     

Extraction and formation dynamic of oak-related volatile compounds from different volume barrels to wine and their behavior during bottle storage

The extraction rate of furfuryl aldehydes, guaiacol, and 4-methylguaiacol, cis- and trans-oak lactone, and vanillin and the formation rate of furfuryl alcohol and the volatile phenols 4-ethylguaiacol and 4-ethylphenol have been studied in wines matured in different capacity oak barrels (220, 500, and 1000 L). Also, the behavior of these compounds during 1 year of wine bottle storage was followed. The lactones were extracted at a linear rate with large differences that depended on barrel volume. Those compounds related to oak toasting (guaiacol, 4-methylguaiacol, furfuryl aldehydes, and vanillin) seemed to be extracted faster during the first days of oak maturation except for vanillin, which required at least 3 months to accumulate in the wine. The volatile phenols, 4-ethylphenol and 4-ethylguaiacol, were formed in large quantities after the first 90 days of oak maturation, coinciding with the end of spring and beginning of summer. Wines matured in 1000-L oak barrels resulted in the lowest levels of volatile compound accumulation. During bottle storage, some compounds decreased in their concentration (5-methylfurfural, vanillin), others experienced increases in their levels (lactones, furfural, 4-ethylguaiacol, 4-ethylphenol), and the concentration of other compounds hardly changed (guaiacol, furfuryl alcohol).     

Influence of wine turbidity on the accumulation of volatile compounds from the oak barrel

In this work the influence of the turbidity of a red wine aged in oak barrels on the accumulation of volatile compounds has been studied. From the results obtained, it may be concluded that the wine turbidity had an effect on the concentration of many of the oak volatile compounds, especially furanic and phenolic compounds. In all cases the concentrations of furanic aldehydes and vanillin were significantly higher (p < 0.01) in the filtered wine than in the unfiltered wine. However, in the unfiltered wine the concentrations of gamma-butyrolactone and eugenol were higher. This difference in the concentrations would be due to the different compositions of the wines and the binding of compounds to some components of the lees. Likewise, it has been observed that the composition of the lees is fundamental in the binding of volatile compounds to the lees as the fermentative lees behave differently from the lees from the wine aging in barrels.     

Water-soluble phenolic substances in soils under several coniferous and deciduous tree species

The humus layer of soils under Betula pendula, Quercus robur, Fagus sylvatica, Pinus nigra and Picea abies was analyzed for water-soluble phenolic substances. Highest concentrations of total water-soluble phenols were found in soils supporting oak trees. Highest polyphenol concentrations occurred under spruce-fir and beech trees, whereas highest monomeric phenols were found in soils under spruce-fir and pine. The polyphenol content was positively correlated with total carbon content of the soil. The phenolic acid composition of the soils under trees was partly dependent on the tree species. Among the monomeric compounds, ferulic, p-coumaric, vanillic, protocatechuic, syringic and benzoic acid dominated the phenol spectra.Seasonal variations were observed in the concentrations of water-soluble and mild alkaline-soluble phenols in the humus layer under F. sylvatica in two contrasting soil types. The water-soluble phenols in a sandy soil accounted for a larger proportion of the mild-alkaline extractable amounts compared to a loamy soil.     

四种栎树EST-SSR信息分析

为开发栎属遗传多样性检测的SSR标记,分析了蒙古栎、无梗花栎、夏栎和欧洲栓皮栎EST-SSR的特点,结果表明蒙古栎的EST中3 209.46 bp有一个SSR,无梗花栎中每6 160.36 bp有一个SSR、夏栎中每5 883.30 bp有一个SSR,欧洲栓皮栎中每6 129.12 bp有一个SSR。蒙古栎、无梗花栎、夏栎和欧洲栓皮栎EST-SSR的平均长度分别为21.65 bp、21.1 bp、20.66 bp和20.65 bp。四种栎类中不同基元的EST-SSR的分布频率具有非常一致的特征,均是二基元、三基元和六基元的SSR分布频率最高,达20%以上。而四基元和五基元的SSR在四个种类中的分布不到0.05%。二基元的SSR中大于1%的SSR均是AG、CT、TC、GA、AT、TA基元,并且在蒙古栎、无梗花栎和夏栎中AG、CT、TC基元的分布频率最高,而在欧洲栓皮栎中是TC、GA、AG的分布频率最高;三基元的SSR中,含CAA、GAA、TCT、CTT的SSR在四种栎类中都存在。六基元的SSR中大于1%在四种栎类中出现的类型均较少,为0～4种。     

Identification of major volatile odor compounds in frankfurters

More than 100 volatile compounds have been identified in the headspace of frankfurter sausages. Most abundant were the terpene hydrocarbons, monoterpene alcohols, phenyl propanoids, and phenols. Separate analyses of solutions of spices and smoke demonstrated that most of the terpenes were derived from the spices, whereas the phenols originated mostly from the smoke ingredients. Many of the compounds contributing to the overall odor of the frankfurters have been identified. Some odors, characteristic of the smokiness and spiciness of frankfurters, were caused by phenols and terpenes, whereas others were due to compounds derived from the meat fraction; these compounds included aldehydes, ketones, furanthiols, and alicyclic sulfur compounds.     

Maturing wines in oak barrels. Effects of origin,volume, and age of the barrel on the wine volatile composition

The influence of the oak origin, volume, and age of the barrel on the volatile composition of a red wine after six months of maturation have been studied. Major volatile compounds in wine were determined using liquid-liquid extraction with dichloromethane, and those volatiles being due to the oak were determined by extraction with pentane-ether using deuterated analogues as internal standards. The results show that there is little difference between the volatile composition of wines matured in French oak barrels and those matured in American oak barrels. The concentration of cis-oak lactone was the most significant difference. The greatest instrumental and sensory differences were found between new and used barrels, with important decreases in lactones and vanillin concentration in used barrels. When studying the effect of the volume of the barrel, the characteristics of the wine matured in 220-L new barrels versus those matured in 1000-L new barrels were very different. In new barrels, the larger the volume of the barrel, the lower the concentrations of those compounds responsible for the oaky aroma. These differences were less evident when comparing wines matured in used barrels with different capacities.     

Environmental Limitations to O3 Uptake - Some Key Results from Young Trees Growing at Elevated Co2 Concentrations

Elevated carbon dioxide concentrations and limited water supply have been shown to reduce the impact of ozone pollution on the growth and physiology of Quercus petraea in a long-term factorial experiment. These responses can be explained by observed reductions in stomatal conductance, and thus potential ozone exposure of 28% and 40% for CO₂ and drought treatments respectively. However, parameterisation of a stomatal conductance model for Quercus robur and Fagus sylvatica grown under ambient and elevated CO₂ concentrations in a separate experiment has demonstrated that elevated CO₂ also reduces the responsiveness of stomata to both saturation deficit (LAVPD) and soil moisture deficit (ψ) in beech, and to a lesser extent, in oak. Season-long model simulations of ozone fluxes suggest that LAVPD and ψ conductance parameters derived at ambient CO₂ concentrations will lead to these fluxes being underestimated by 24% and 2% for beech and oak respectively at 615 ppm CO₂.     

Changes in amine concentrations during aging of red wine in oak barrels

This investigation studied the evolution of amines in red wines made with Merlot variety, during aging in American oak barrels (Quercus alba) and in French oak barrels (Quercus sessilis) from the Allier and Nevers regions. From the results obtained it was observed that the evolutions of the amines were similar in all three types of oak woods. Histamine and tyramine were produced at the beginning of the aging process, although they were not accumulated in the wines, probably due to their degradation. Putrescine was the most abundant amine in the wines; its concentration increased to an important extent during aging as it did not undergo degradation. The concentration of cadaverine increased slightly at the first stage of aging and, like putrescine, did not degrade at all. The volatile amines showed slight variations during aging, although in no cases were high accumulations observed in the wines. Dimethylamine and isobutylamine were degraded during storage in the barrels.