Oak Wood Species Research Articles

Evaluation of non-anatomical characteristics for wood identification of six Korean oak species

Summary This study aimed to investigate and compare the non-anatomical characteristics of six Korean oak wood species (Quercus variabilis, Q. serrata, Q. mongolica, Q. dentata, Q. aliena and Q. acutissima) to provide identification keys and quality indices for the effective utilization of these species. Non-anatomical characteristics, including heartwood fluorescence, fluorescence and color of water and ethanol extracts, froth test, chrome azurol S test and burning splinter test, were evaluated according to the International Association of Wood Anatomists (IAWA) lists. None of the six Korean oak species displayed heartwood fluorescence or fluorescence in the ethanol extract. Only Q. serrata exhibited bright blue fluorescence in the aqueous extract. Each species showed distinct colors in both water and ethanol extracts, and the water extract of all species was darker than that of the ethanol extract. A weak positive reaction in the froth test was observed only for Q. serrata. Furthermore, Q. variabilis and Q. acutissima showed positive reactions to both heartwood and sapwood in the chrome azurol S test. The burning splinter test revealed that only Q. acutissima was transformed into charcoal. Thus, water extract fluorescence and color, ethanol extract color, froth test, chrome azurol S test, and burning splinter test can be used to identify the six Korean oak species.

Radial Variation of Wood Anatomical Characteristics and Maturation Ages of Six Korean Oak Species

The objective of this study was to examine and compare radial variation of the anatomical characteristics and the transition age from juvenile to mature wood of the six Korean oak wood species: Quercus variabilis (Qv), Quercus serrata (Qs), Quercus mongolica (Qm), Quercus dentata (Qd), Quercus aliena (Qal), and Quercus acutissima (Qac). Quantitative anatomical features were observed from the pith to the bark at five growth-ring intervals using optical microscopy. A segmented regression model was used to evaluate the transition from juvenile wood to mature wood. The clearest transition from juvenile to mature wood was observed in the radial variation of the earlywood vessel diameter and fiber length. The maturation age of the six Korean oak species ranged from 19 to 44 years. Qv exhibited the highest values for latewood vessel diameter, fiber length, and fiber diameter. Qac displayed the highest values for earlywood vessel diameter and fiber wall thickness. The highest fiber lumen diameter was observed for Qm. The differences in earlywood and latewood vessel diameters and fiber lengths could be utilized as identification keys for these species. Earlywood vessel diameter and fiber length have emerged as the most reliable indicators for estimating the transition from juvenile to mature wood.

Macroscopic and Microscopic Anatomical Characteristics of Six Korean Oak Species

The macroscopic and microscopic anatomical characteristics of wood impact its utilization. This study investigated and compared the anatomical characteristics of six Korean oak wood species: Quercus variabilis, Quercus serrata, Quercus mongolica, Quercus dentata, Quercus aliena, and Quercus acutissima. Microscopic anatomical characteristics were evaluated according to the International Association of Wood Anatomists’ list for hardwood identification. Q. variabilis had a corky bark texture, with a color similar to that of Q. serrata. Flat ridges and shallow-fissured barks were observed in Q. serrata and Q. mongolica. The heartwood color was darker than that of sapwood in all species, with color variations. Q. variabilis had heartwood–sapwood colors similar to those of Q. acutissima, while Q. mongolica and Q. aliena presented similar heartwood–sapwood colors. Concerning microscopic features, Q. variabilis and Q. acutissima exhibited similar latewood vessel arrangements, featuring diagonal and/or radial patterns. In contrast, dendritic-to-diagonal patterns of vessels with angular outlines were observed in Q. serrata, Q. mongolica, Q. dentata, and Q. aliena. Additionally, Q. variabilis and Q. acutissima had vasicentric, confluent, and unilateral paratracheal axial parenchyma in the latewood. In summary, bark morphology, bark color, wood color, and latewood vessel characteristics can be used as identification keys for Korean oak species.

Investigation of color parameters in pine, limba, sapele, iroko, oak, and beech wood species exposed to outdoor conditions in Van city, Turkey

Sapele, pine, limba, iroko, beech, and oak wood species are important species used indoors and outdoors, as supplied by furniture companies. It is known that the color changes in wood material when exposed to the external environment. This is an important factor for the outdoor use of wood material. In this study, the color parameters of Scotch pine (Pinus sylvestris L.), oriental beech (Fagus orientalis L.), limba (Terminalia superba Engl. et Diels), sapele (Entandrophragma cylindricum), sessile oak (Quercus petraea L.), and iroko (Milicia excelsa) wood species, which are used in both indoor and outdoor woodworking industries in Van city, Turkey were investigated after exposing them to natural weather conditions for 9 months in outdoor conditions. Each type of wood exhibited a different color behavior in outdoor conditions. In sapele and limba wood species, b* and a* values increased and L* values decreased with increasing weathering time. It was observed that ∆E* increased with increasing time of exposure in all tree species. At the end of 9 months of weathering, the highest ∆E* value was determined in pine wood, followed by beech, sapele, limba, iroko, and oak wood species, respectively.

Influence of Oak Species, Toasting Degree, and Aging Time on the Differentiation of Brandies Using a Chemometrics Approach Based on Phenolic Compound UHPLC Fingerprints.

Oak wood is the main material used by coopers to manufacture casks for the aging of spirits or wines. Phenolic compounds are the main components extracted from the wood during spirit aging. In the present study, a chemometric approach based on unsupervised (PCA) and supervised (PLS-DA) pattern recognition techniques has been applied to the chromatographic instrumental fingerprints, obtained by ultra-high-performance liquid chromatography (UHPLC) at 280 nm, of the phenolic profiles of brandies aged in casks made of different oak wood species. The resulting natural data groupings and the PLS-DA models have revealed that the oak wood species, the toasting level, and the aging time are the most influential factors on the phenolic profile of the final products. Fingerprinting should be considered as a very useful feature, as it represents a considerable advantage, in terms of internal and quality control, for brandy producers.

Influence of Different Wood Chip Extracts Species on Color Changes and Anthocyanin Content in Synthetic Wine Solutions.

There is restricted knowledge about the potential impact of the use of different wood species on color and anthocyanin changes during the red wine aging process. This lack of knowledge is even greater when no oak wood species are used. Thus, the aim of this study was to carry out a comparative analysis of the impact of wood chip extracts from oak, acacia, and cherry species on the color characteristics and anthocyanins changes using synthetic wine solutions. In this context, several methodologies were used to quantify, color, and anthocyanins changes during the aging time studied. The results indicated that the contact between wood chip extracts and grape skin isolated anthocyanin extracts induced a decrease of color intensity (particularly red color), and the anthocyanin content in the different experimental synthetic wine solutions studied. All chromatic modifications are potentially detected by human eyes because ΔE values were much higher than 3 CIELab units. These tendencies seem to be independent of the wood species used, but are more pronounced for higher contact time between wood chip extracts and anthocyanins. The obtained results may contribute to a better understanding of the chromatic changes of red wines when aged in contact with different wood chip species.

New Strategies to Improve Sensorial Quality of White Wines by Wood Contact

Ageing wine is a common practice used in winemaking, since the quality and sensory profile increase due to the extractable compounds coming from wood, by means of barrels or chips. The quantitative and qualitative compounds of the wood depend on the species, its origins and the treatments applied in cooperages. Traditionally, oak wood species are most often used in cooperage, specifically Quercus alba (Q. alba), Known as American oak and Quercus robur (Q. robur) and Quercus petraea (Q. petraea), both known as French oak. Although this stage is very common for red wines, its use is still restricted in the case of white wines. However, this topic is particularly interesting, since due to the sensorial benefits of wood contact, the option for ageing white wines in barrels or chips could be chosen by winemakers. This review compiles the novel strategies applied to white wines by means of wood contact in recent years with the aim to increase wine quality and sensorial features.

Characterization of the Oxygen Transmission Rate of Oak Wood Species Used in Cooperage.

The oxygen that wine receives while aged in barrels is of interest because it defines the reactions that occur during aging and, therefore, the final properties of the wine. This study is intended to make up for the lack of information concerning the oxygen permeability of eight different woods of Quercus alba L. and Quercus petraea (Matt.) Liebl. commonly used. In addition, it shows how oxygen transfer evolves with the liquid contact time during testing under similar aging conditions to those in wine barrels. French oak woods permitted a higher oxygenation rate than American ones in all cases. A decrease in the oxygen entry caused by impregnation of the wood during the process was observed in all of the species studied. This process is determined by the thickness of the flooded wood layer containing free water, although differently in the two species, possibly due to the anatomical structure and the logging process for each.

Influencia de los radios en algunas propiedades físicas y mecánicas de la madera de ocho encinos (Quercus) de Durango, México

Se presenta la relación del parénquima radial (radios uniseriados y multiseriados) con la contracción volumétrica y las propiedades mecánicas de flexión, compresión paralela y perpendicular y el cortante paralelo de la madera de ocho especies de encinos de Durango, México. Para determinar la relación de los radios con las propiedades tecnológicas, se hizo un análisis de regresión multivariado en 3 donde las variables dependientes fueron los valores anatómicos y las independientes los valores físicos y mecánicos. Los resultados muestran que la altura y anchura de los radios multiseriados son los caracteres anatómicos de mayor influencia en las propiedades tecnológicas. Se resalta que en la selección de la madera de encino para su aprovechamiento, se deben considerar las características anatómicas, físicas y mecánicas, que influyen en su manejo para aprovechar de manera óptima este recurso y lograr la conservación de los encinares y preservar el equilibrio ecológico de los sitios donde crecen.

Aging practices influence chemical and sensory quality of cachaça

Aging practices have significant impact on the final quality of spirits. Wood species, barrel toasting intensity, and maturation period are the key factors that can modify the chemical composition and sensory properties of aged spirits. This study aimed to evaluate the influence of oak wood species, as well as toasting intensity of new barrels made of them, on the development of chemical compounds and sensory quality attributes of cachaça aged for as long as 24months in toasted American (Quercus alba) and French (Quercus petraea) oak barrels. American oak barrels were submitted to medium toasting and French oak barrels underwent medium and heavy toasting. Sensory quality was assessed by comparative and descriptive tests using Flash Profile. Cachaças aged in barrels made of French oak and American oak could be distinguished mainly by the content of acetic acid, but also by the different contents of maturation congeners. Toasting intensities were responsible for modulating the chemical composition and influencing the sensory attributes. The ideal period of aging was achieved at about 15 to 24months, when the maturation congeners reached a better point of stabilization.

Evaluation of the antioxidant activities of different bio-oils and their phenolic distilled fractions for wood preservation

This research investigated the antioxidant activities of raw bio-oils produced from pine and oak wood species. The study also included the effect of the pyrolysis parameters on the properties of the bio-oils produced. In addition to raw bio-oils, phenolic fractions were further isolated from the bio-oils at two different temperature ranges (180–220 °C and 220–270 °C) by using spinning band distillation columns. The antioxidant activities of raw bio-oils and phenolic fractions were evaluated using the Trolox equivalent antioxidant capacity (TEAC) assay. The concentrations of phenolic compounds were determined by gas chromatography/mass spectrometry (GC/MS). The results of the assay showed that the antioxidant activities of the phenolic fractions are much higher than those of the parent bio-oils. GC/MS analysis results showed that o-guaiacol and its derivatives (4-methylguaiacol, 4-ethylguaiacol, and 4-propylguiacol), phenol, 3-methylphenol, 2,3-dimethylphenols, 3-ethylphenol, and eugenol are the most influential phenolic compounds on the antioxidant activity of the bio-oils and their distilled fractions.

Optimization of the steam explosion and enzymatic hydrolysis for sugars production from oak woods

Fermentable sugars production from three kind of steam-exploded oak wood was optimized by Response Surface Methodology (RSM), using the severity factor (R0), the pretreated total solids (TS%) and the enzyme loading (EL%) as variables of a central composite design. A total of 17 experiments for each biomass were carried out. The optimal conditions established with RSM were: severity, 4.46 for holm, 4.03 for turkey oak and 3.92 for downey oak; total solids, 5.4% for holm, 5.0% for turkey oak and 12.7% for downey oak; and enzyme concentration, 9.6% for holm, 15.0% for turkey oak and 15.0% for downey oak. Under these conditions, the model predicted an overall sugar yield of 67.1% for holm, 79.9% for turkey oak and 68.4% for downey oak. The results of the confirmation experiments under optimal conditions agreed well with model predictions. Oak wood species may be a good feedstock for the production of reducing sugars.

Study of phenolic potential of seasoned and toasted Portuguese wood species (<em>Quercus pyrenaica</em> and <em>Castanea sativa</em>)

<p style="text-align: justify;"><strong>Aim</strong>: The phenolic potential and suitability of seasoned and toasted Portuguese chestnut (<em>Castanea sativa</em> Mill) and oak wood (<em>Quercus pyrenaica</em>) as alternative cooperage materials were evaluated.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Low-molecular-weight phenols and ellagitannins from seasoned and toasted Portuguese wood species were analysed by HPLC. <em>C. sativa</em> was found to be richer in phenolic compounds than <em>Q. pyrenaica</em>. High concentrations of vescalagin and gallic acid were specific to <em>C. sativa</em>. Toasting significantly reduced the ellagitannin content in both wood types, albeit less markedly in <em>C.</em> <em>sativa</em>. As regards phenolic aldehydes, <em>C. sativa</em> contained substantially greater amounts of vanillic aldehyde, an odour-active compound, than <em>Q. pyrenaica</em>.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Both types of Portuguese wood are suitable for use as cooperage materials, although chestnut wood is better suited to the heat treatment involved in the coopering process.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Portuguese wood species provide an effective alternative to the oak wood species traditionally used for aging alcoholic beverages.</p>

Antioxidant capacity, scavenger activity, and ellagitannins content from commercial oak pieces used in winemaking

In 2005, the European Union authorized the use of oak wood pieces in winemaking, and consequently, the addition of oak chips has been generalized. Thus, the antioxidant capacity, scavenger activity, and ellagitannins content from fourteen different commercial oak wood pieces (Quercus spp.) that can be found on the Portuguese market as alternatives to barrels for aging wines were studied. Commercial oak wood pieces samples from Quercus petraea had significantly higher antioxidant activity values than the pieces from Quercus alba species. In general, antioxidant capacity and scavenging activity decrease with the toasting level of the oak wood pieces samples analyzed. A similar effect was detected in the individual ellagitannin content studied. On the other hand, with the toasting process, the total phenolic content and the ellagic acid concentration increased. Finally, a correlation analysis revealed that ellagitannins contribute to the antioxidant capacity of oak wood pieces studied. From the data presented in this paper, antioxidant capacity and ellagitannin content of the oak wood pieces studied have been clearly related either to the oak wood species used, particle size, or to toasting levels.

Aromatic potential of Castanea sativa Mill. compared to Quercus species to be used in cooperage

The composition of volatile and semi-volatile compounds of chestnut (Castanea sativa Mill.) was studied and compared to oak wood species frequently used in cooperage (Quercus alba, Quercus petraea, Quercus robur and Quercus pyrenaica) to evaluate its aromatic potential. Chestnut was found to be a suitable wood for use in ageing processes, based on the large, diverse number of detected compounds (e.g., lactones, furanic compounds, terpenes, lignin derivatives and triterpenic compounds). Chestnut wood possessed high levels of volatile phenols and phenolic aldehydes, specifically vanillin and its derivatives. Each wood species exhibited a characteristic, quantifiable composition of volatile compounds, and therefore, the sensorial profile of each wood species is expected to be different. The levels of certain volatile compounds were also useful for discriminating among the studied wood species.

RESISTENCIA AL IMPACTO DE LA MADERA DE DIEZ ENCINOS (Quercus) MEXICANOS

Impact resistance or toughness values are presented for ten oak wood species from four Mexican states (Jalisco, Mexico, Puebla and Veracruz) tested in green condition with a FPL machine. No significant differences were detected in the toughness values among individuals of the same species growing in different regions of the country; therefore, a common value can be established for those species. There is a directly proportional effect of specific gravity on toughness, which is enhanced by including the thickness values of the cell wall as an additional independent variable in multiple regression analysis. Finally, values of the anatomical, physical and mechanical characteristics of Quercus crassipes wood are presented.

Classification of Red Oak (Quercus Rubra) and White Oak (Quercus Alba) Wood Using a near Infrared Spectrometer and Soft Independent Modelling of Class Analogies

In this study, a method suitable for online rapid classification and separation of red oak and white oak wood species has been developed with the use of near infrared (NIR) spectroscopy and soft independent modeling of class analogies (SIMCA). The spectra of 150 wood specimens of each species were collected over wavelength window of 800–2500 nm. The raw spectra and spectra pre-treated by first derivative and standard normal variate (SNV) transformation were used to develop calibration models using the wavelength ranges 800–2500 nm, 1100–2200 nm and 1400–1900 nm by the SIMCA method. Principal component analysis (PCA) models were made for each class from the calibration set consisting of 100 specimens of red oak and white oak, respectively, and specimens not present in the calibration set (Testing set) consisting of 100 specimens were tested for classification according to the SIMCA method at the 5% and 25% significance level. Type I error (rejection of true member) associated with the models developed ranged from 2% to 20% and from 16% to 66%, respectively, for 5% and 25% significance level, while type II error (acceptance of a false member) was 0% for all models developed. There was no significant improvement in models developed with spectra pre-treated with first derivative or standard normal variate transformation over models developed with raw spectra. The full NIR spectral region of 800–2500 nm provided the most useful information for distinguishing between the two species. The results of this study showed that NIR spectroscopy coupled with the SIMCA method of multivariate data analysis could be used to reliably separate and sort wood of red oak and white oak.

Volatile composition analysis by solid-phase microextraction applied to oak wood used in cooperage (Quercus pyrenaica and Quercus petraea): effect of botanical species and toasting process

The purpose of this study was to investigate the sorption of selected volatile substances from oak wood-chip samples (Quercus pyrenaica Willd. and Quercus petraea L.) subjected to different toasting levels, namely, without toasting, with medium toasting, and with strong toasting, through the use of solid-phase microextraction (SPME). The main volatile compounds identified as a function of the toasting level and botanical species were furfural, hexanal, α-pinene, d-limonene, decanal, vitispirane, ethyl hexanoate, cis-3-methyl-γ-octalactone (“oak lactone” or “whisky lactone”), α-terpineol, p-xylene, and nonanal. Considering the data obtained from the toasted woods (medium and strong intensity) in comparison with those of nontoasted woods, it can be pointed out that the average peak area and the number of compounds identified in the gas chromatogram decreased during the toasting process. In general, regarding the compounds analyzed, quantitative differences were found between the two oak wood species under study. High values of volatile compounds were found in Quercus pyrenaica oak wood chips. In addition, for the number of compounds identified in oak wood extracts and directly extracted from solid oak wood chips by SPME, it is concluded that the best extraction process for volatile compounds from oak wood is the use of oak wood-chip liquid extracts.

Evolution of phenolic composition and sensory properties in red wine aged in contact with Portuguese and French oak wood chips

<p style="text-align: justify;">A red wine was matured in contact with 4 g/L of oak wood chips from Portuguese (Quercus pyrenaica Willd.), French (Quercus petraea L.) and a mixture (50:50) of this two oak wood species, during 13 weeks, in order to evaluate the effects of these different oak wood chip species (specially Portuguese oak wood) on the phenolic composition evolution of the wine and in their sensory properties. In general, for the phenolic compounds studied, it wasn't possible to detect remarkable differences between the control wine (aged without oak wood chips) and the wines aged in contact with the two oak wood chips species used. However, for non-flavonoid phenols, the presence of oak wood chips contributed to an increase of these compounds in red wines. The influence of oak wood chips in anthocyanins evolution were similar for all wines, except for malvidin-3-glucoside, which decrease was more evident for the wine aged in contact with oak wood chips. The oak wood chips species and the chips concentration used in this study, didn't affect the proanthocyanidin contents in the wines during the time considered.</p><p style="text-align: justify;">Sensory results showed that, the wines aged in contact with Portuguese and French oak wood chips and the mixture of this two oak wood species, differed significantly from the control wine in several sensorial characteristics. The wines aged in contact with wood chips showed a higher punctuation values for intensity, toasted, wood and vanillin aroma, taste intensity and global appreciation. This positive effect was more evident for wines aged with Portuguese oak wood chips. Probably this results, suggest that the Portuguese oak wood samples species (Quercus pyrenaica Willd.) used could be considered suitable for barrel production because it has a positively effect in sensorial red wine attributes. Thus with this study we tried to contribute for understand the Portuguese oak wood role in red wine characteristics.</p>

Pyrolysis–gas chromatography/mass spectrometry of Quercus sp. wood : Application to structural elucidation of macromolecules and aromatic profiles of different species

Analytical pyrolysis was applied to oak wood to provide useful information concerning the structure of oak wood components and the corresponding extractable polymers (lignins, polysaccharides). We have established the aromatic profile of the formed products during heating and also the chemotaxonomy of different oak wood species, focusing on the qualitative and quantitative aspects.