Search

The effects of air heat treatment were evaluated on six Korean oak woods: Quercus serrata (Qs), Quercus mongolica (Qm), Quercus acutissima (Qac), Quercus aliena (Qal), Quercus dentata (Qd), and Quercus variabilis (Qv). Color change (ΔE*), weight loss, and density loss were examined using flat-sawn heartwood boards before and after treatment at 160 °C, 180 °C, 200 °C, and 220 °C for 2 h. Overall, the ΔE*, weight loss, and density loss increased with temperature. The properties between temperature and species showed distinct differences. A change to a darker color was observed in all species after treatment at 200 °C. Qm and Qd exhibited the highest and lowest L*, a*, and b* values after treatment at 220 °C, respectively. The highest ΔE* values were obtained in Qd at 160 °C, Qs at 180 °C and 200 °C, and Qv at 220 °C. Qd and Qv exhibited the highest and lowest weight losses at 160 °C, respectively. Qac and Qal showed the highest and lowest weight losses at 220 °C, respectively. Qm showed the highest density loss at all temperatures, whereas Qs had the lowest at 160 °C, and Qac had the lowest values at 180 °C, 200 °C, and 220 °C.

The production of high-quality aged marc spirits includes a minimum period of six months of ageing in oak barrels. Lastly, producers are interested in alternative botanical origin wood. The present study is aimed at investigating the influence of Greek oak (Quercus trojana) and Greek chestnut (Castanea sativa) compared with French (Quercus petraia) and American oak (Quercus alba) on the chemical composition and sensorial characteristics of aged tsipouro, produced from marc from the Black Muscat variety. Gas chromatography–olfactometry–mass spectrometry (GC–O–MS) was used to identify volatile compounds of the aged tsipouro. Also, colour and polyphenol measurements were made, and an organoleptic evaluation was performed by 16 trained tasters. The findings revealed rather similar results between the tsipouro made from different wood species, especially between Greek and French oaks, and relative differentiation for that of chestnut. All the aged distillates exhibited a pleasant and rich aromatic potential, dominated by floral and fruity terpene varietal aromas as well as wood-related volatiles. Chestnut, with a high phenolic potential, gives pleasant organoleptic effects over time and can be an alternative wood for ageing spirits. This research highlights the importance of wood selection in the tsipouro ageing process and enables the use of Greek wood species in the ageing of spirits.

There is a trend towards the commercialisation of strawberry tree fruit spirit (AUS) with wood ageing, motivated by its favourable sensory characteristics. Additionally, further studies are necessary to elucidate the optimal conditions regarding ageing time and toasting level. This study evaluated the changes in colour and low molecular weight compounds (LMWC) of AUS aged for three and six months using oak wood (Quercus robur L.) with light, medium and medium plus toasting levels. For this purpose, phenolic acids (gallic, ellagic, ferulic and syringic acids), phenolic aldehydes (vanillin, syringaldehyde, coniferaldehyde and sinapaldehyde) and furanic aldehydes (furfural, 5-hydroxymethylfurfural and 5-methylfurfural) were quantified using the HPLC method. Chromatic characteristics, colour sensory analysis and total polyphenol index were also analysed. Fourier transform near-infrared spectroscopy (FT-NIR) was used to discriminate between samples. The results emphasized the favourable effect of oak wood contact on enhancing the colour and enriching AUS with low molecular weight compounds (LMWC). AUS aged in medium toasted wood exhibits high levels of total phenolic index, 5-hydroxymethylfurfural, furfural, coniferaldehyde, sinapaldehyde, sum LMWC and chromatic characteristics b* and C. Concentrations of syringaldehyde, ellagic acid, vanillin and syringic acid and a lighter colour (a* chromaticity coordinates) are higher in AUS aged with slightly more toasted wood. Nearly all analysed parameters showed an increase with ageing time. The FT-NIR technique allowed for the differentiation of aged AUS, focusing more on ageing time than on toasting level.

Microencapsulated phase change materials (MPCMs) incorporated into oak wood via vacuum impregnation have shown promise as thermal energy storage (TES) materials. Physical and chemical properties of MPCMs and resulting Phase Change Energy Storage Wood (PCESW) were analyzed. Scanning electron microscopy and particle size analyses revealed similar particle sizes, while X-ray diffraction (XRD) and Fourier transform infrared spectra confirmed crystal phase and chemical structure. Thermal gravimetric analysis (TGA) and differential scanning calorimetry determined thermal properties, including phase change temperature, enthalpy, thermal stability, and conductivity. The MPCMs exhibited a phase change enthalpy of 146.0 J/g and temperature of 35.0 °C, with excellent thermal stability. The FTIR, XRD, and TGA analyses showed unchanged chemical structure, crystallinity ratios, and decomposition in two stages, respectively. The PCESW exhibited a latent heat storage of 3.02 J/g at 25.4 °C. Decay tests demonstrated noticeably reduced weight loss (1.22% and 1.55%) for MPCMW samples treated with Trametes versicolor and Coniophora puteana, compared to unleached control samples (19.7% and 20.8%). These findings indicate the high efficiency and potential of PCESW as a thermal energy storage material.

Microencapsulated phase change materials (MPCMs) incorporated into oak wood via vacuum impregnation have shown promise as thermal energy storage (TES) materials. Physical and chemical properties of MPCMs and resulting Phase Change Energy Storage Wood (PCESW) were analyzed. Scanning electron microscopy and particle size analyses revealed similar particle sizes, while X-ray diffraction (XRD) and Fourier transform infrared spectra confirmed crystal phase and chemical structure. Thermal gravimetric analysis (TGA) and differential scanning calorimetry determined thermal properties, including phase change temperature, enthalpy, thermal stability, and conductivity. The MPCMs exhibited a phase change enthalpy of 146.0 J/g and temperature of 35.0 °C, with excellent thermal stability. The FTIR, XRD, and TGA analyses showed unchanged chemical structure, crystallinity ratios, and decomposition in two stages, respectively. The PCESW exhibited a latent heat storage of 3.02 J/g at 25.4 °C. Decay tests demonstrated noticeably reduced weight loss (1.22% and 1.55%) for MPCMW samples treated with Trametes versicolor and Coniophora puteana, compared to unleached control samples (19.7% and 20.8%). These findings indicate the high efficiency and potential of PCESW as a thermal energy storage material.

The world’s expanding population presents a challenge through its rising demand for wood products. This requirement contributes to increased production and, ultimately, the high-quality and efficient utilization of basic materials. Detecting defects in wood elements, which are inevitable when working with a natural material such as wood, is one of the difficulties associated with the issue above. Even in modern times, people still identify wood defects by visually scrutinizing the sawn surface and marking the defects. Industrial scanners equipped with software based on convolutional neural networks (CNNs) allow for the rapid detection of defects and have the potential to accelerate production and eradicate human subjectivity. This paper evaluates the suitability of defect recognition software in industrial scanners against software specifically designed for this task within a research project conducted using Adaptive Vision Studio, focusing on feature detection techniques. The research revealed that the software installed as part of the industrial scanner is more effective for analyzing knots (77.78% vs. 70.37%), sapwood (100% vs. 80%), and ambrosia wood (60% vs. 20%), while the software derived from the project is more effective for analyzing cracks (70% vs. 65%), ingrown bark (42.86% vs. 28.57%), and wood rays (81.82% vs. 27.27%).

This study determined the impact of undertaking an initial treatment of oak wood by sealing its surface pores with epoxy resin, focusing on the durability of transparent coating systems when exposed outdoors. Throughout the exposure period, various parameters including color, gloss, surface wettability, and both macroscopic and microscopic surface evaluation were continuously monitored. The study involved two sets of samples: one set underwent the pretreatment, while the other did not. Subsequently, four coating systems were applied to the samples, comprising two solvent-based and two water-based coatings. The experiment was conducted over a period of two years, utilizing natural weathering methods within the premises of the Czech University of Life Sciences in Prague. The pretreatment with epoxy resin exhibited enhanced durability for all paint systems. The analysis showed a significant difference in gloss and color after 12 months of weathering exposure without any significant effect on surface wettability and sealing. However, after 24 months of the weathering exposure, no significant differences between the sealed and unsealed surface were observed. The most significant change in properties was noted for the water-based coatings used in coating systems number 3 and 4, and these coatings were rated as the best.

The work investigates the effects of CO2 laser parameters (laser power and raster density) on wood mass loss in oak wood and impacts on its morphology, chemical structure, and surface properties (colour and hydrophilicity). The energy amount supplied onto the wood surface with a laser beam under different combinations of the irradiation parameters was expressed through a single variable—total irradiation dose. The mass loss was confirmed as linear-dependent on the irradiation dose. With the mass reduction, the roughness was enhanced. The roughness parameters Ra and Rz increased linearly with the mass loss associated with the increasing irradiation dose. The FTIR (Fourier transform infrared spectroscopy) spectroscopy also detected chemical changes in the main wood components, influencing primarily the wood colour space. Conspicuous discolouration of the engraved wood surface was observed, occurring just at the minimum laser power and raster density. The additional increasing of laser parameters caused a novel colour compared to the original one. The detected dependence of wood discolouration on the total irradiation dose enables us to perform targeted discolouration of the oak wood. The engraved surfaces manifested significantly better wettability with standard liquids, both polar and non-polar, and higher surface energy values. This guarantees appropriate adhesion of film-forming materials to wood. Identification of the changes in wood surface structure and properties, induced by specific CO2 laser-treatments, is important for obtaining targeted discolouration of the wood surface as well as for the gluing or finishing of the surfaces treated in this way.

The blending of wine spirits (WSs) produced in different ageing conditions is a key operation to impart specific features, enhance complexity, increase the final product’s quality and ensure brand consistency over the years, but requires time, labour and experienced blenders. This work aimed to develop a novel technology, natural blending, towards innovation and a more sustainable production process, adding value to the final product. WSs were aged in 250 L barrels and in 1000 L stainless steel tanks with wood staves and micro-oxygenation (MOX), using Limousin oak and chestnut wood simultaneously at a 50:50 ratio (natural blending) and separately; after 18 months of ageing, the last ones underwent the blending operation at the same ratio. All WSs were bottled and thereafter the following traits were analysed: alcoholic strength, acidity, dry extract, total phenolic index, low molecular weight compounds by HPLC method, chromatic characteristics and sensory profile. No significant differences in the physicochemical characteristics and sensory profile between the WSs resulting from the two blending technologies were found. Natural blending did not induce changes in the characteristics imparted by each ageing technology. These findings point to natural blending as a reliable alternative to the blending operation, especially in combination with ageing in tanks with staves and MOX.

This study evaluated within-stem differences in the moisture content of stored summer-harvested oak wood with respect to drying method. The felled oaks were naturally dried for eight weeks, from 4 July to 29 August 2017. We analyzed two methods of preparation and storage: a transpiration drying method (W), and an air-drying method for stem-wood (L). Transpiration drying is a better method for oak stems than air-drying. Statistically significant differences between drying methods were found after six weeks of storage. This coincided with complete wilting of the leaves. However, signs of wilting and leaf color change appeared earlier, between the second and fourth weeks of storage. In parallel, in scenario W, a statistically significant difference in MC of sapwood was observed between the second and fourth weeks of storage. Such a phenomenon was not observed in scenario L. The MC of heartwood also gradually decreased, especially in scenario W. Explanation of this phenomenon lay outside the scope of this study; however, it indicates how the structure and properties of wood, in addition to storage conditions and methods, influence the efficiency of biomass drying in the harvesting area.

Ellagitannins are signature constituents of oak wood and their consumption has been associated with various health benefits. In vivo, they undergo metabolic degradation including gut microbial metabolism yielding urolithins. Only limited data is available about compounds being present in blood after intake of an extract from French oak wood, Robuvit®. In the course of a randomized, double-blind, controlled clinical investigation, 66 patients undergoing hysterectomy received placebo or 300 mg Robuvit® per day before and over 8 weeks after surgery. Serum and blood cell samples were analyzed by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The number of urolithin producers and the urolithin levels increased after intake of Robuvit®. In serum samples, the median concentration of urolithin A was 14.0 ng/ml [interquartile range (IQR) 57.4] after 8 weeks. Urolithin B was determined at 22.3 ng/ml (IQR 12.6), urolithin C at 2.66 ng/ml (IQR 2.08). In blood cells, lower concentrations and only urolithins A and B were detected. A statistically significant association of lower post-surgical pain scores with metabotype A was detected (p < 0.05). To conclude, supplementation with French oak wood extract raised urolithin generation in patients and suggested health advantages for urolithin-producers.

This paper examines the effect of selected factors on the wood bonded joint strength. The structural factor under scrutiny was the geometry of the surface area; however, other major dimensions of adherends were compared as well. The tests were performed on 6 joint types: butt, v-shaped, interlocking, scarf, tongue & groove, and single lap joints, which were formed on two types of substrate materials – pine and oak wood, and adhesively bonded. The joints were bonded with Prefere 6312 wood adhesive and Loctite 3430 two-component epoxy adhesive. Strength testing of the joints was performed on Zwick/Roell Z150 material testing machine, according to DIN EN 1465 standard. The results obtained from the tests indicate that bonded joints of oak wood exhibit higher strength properties than those of pine wood adherends, which was confirmed in nearly all strength tests.

The paper deals with the assessment of the age of oak wood (0, 10, 40, 80 and 120 years) on its fire resistance. Chemical composition of wood (extractives, cellulose, holocellulose, lignin) was determined by wet chemistry methods and elementary analysis was performed according to ISO standards. From the fire-technical properties, the flame ignition and the spontaneous ignition temperature (including calculated activation energy) and mass burning rate were evaluated. The lignin content does not change, the content of extractives and cellulose is higher and the content of holocellulose decreases with the higher age of wood. The elementary analysis shows the lowest proportion content of nitrogen, sulfur, phosphor and the highest content of carbon in the oldest wood. Values of flame ignition and spontaneous ignition temperature for individual samples were very similar. The activation energy ranged from 42.4 kJ·mol−1 (120-year-old) to 50.7 kJ·mol−1 (40-year-old), and the burning rate varied from 0.2992%·s−1 (80-year-old) to 0.4965%·s−1 (10-year-old). The difference among the values of spontaneous ignition activation energy is clear evidence of higher resistance to initiation of older wood (40- and 80-year-old) in comparison with the younger oak wood (0- and 10-year-old). The oldest sample is the least thermally resistant due to the different chemical composition compared to the younger wood.

Adega do Casal Manteiga is a winery, publicly owned by the Municipality of Oeiras that produces Carcavelos fortified wine. Carcavelos fortified wine is an appellation of origin and demarcated as D.O.P. (Denominação de Origem Protegida). This study examines the effects of barrels made from botanical species (Quercus pyrenaica, and Quercus robur) and toasting method (medium and high) on a single vintage wine that has been aged for 8 years. Twenty barrels were used, with five replicates for each factor. The barrels were fabricated and toasted using the same cooperage, J.M. Gonçalves in Portugal. Significant differences were seen between the species Q. robur and Q. pyrenaica, with an impact on total phenolic content, including both flavonoids and non-flavonoids. The total phenols of the wine aged in Q. pyrenaica barrels was significantly higher than in the Q. robur barrels, and Q. pyrenaica contained more flavonoids than Q. robur in medium and high toast barrels. Q. pyrenaica showed more non-flavonoid compounds than Q. robur inhigh and medium toasted barrels, but this difference in non-flavonoids was only statistically significant in the high toasted barrels. The degree of toasting had significant effects on the flavonoid content of the wine, as well as the tanning power. Flavonoid content increased for both Q. pyrenaica and Q. robur in the wines that were aged in high tasted barrels compared to those that were medium toasted. The tannin power decreased for both Q. pyrenaica and Q. robur when the toasting increased.

Brandy de Jerez is a European Geographical Indication for grape-derived spirits aged in oak casks that have previously contained any kind of Sherry wine and, therefore, are known as Sherry Casks®. Wood compounds have a substantial influence in the quality of the brandies that are aged in the barrels. In the cellar, the barrels that have been used for many years to keep Sherry wine or other wine spirits are often used for this purpose. When wooden barrels are used for the first time, they release a large amount of compounds into the liquid contained in them. Such amount decreases over time but casks life cycle has remained unexplored until now. The present work has the aim to study the brandies obtained from the same wine spirit after two years ageing in three differently oak casks: namely new, 7 years of use (4 years containing Oloroso wine and 3 years containing wine spirits) and 32 years of use (8 years containing Oloroso wine and 24 years containing wine spirits). According to the results from our experiments, even after 32 years of use, the wood barrels still contribute to modify the organoleptic characteristics of brandy. Moreover, the brandies aged in used barrels were judged more balanced than those aged in new barrels.

A barrier plasma, created at atmospheric pressure, was used to improve the surface and adhesive properties of polyester (PES) film with respect to wood using polyurethane adhesives. The modification of PES film surfaces using barrier discharge plasma is attractive for various applications. Plasma pre-treatment initiates and participates in grafting, polymerization, or cross-linking reactions on the PES surface. This method of surface modification is clean, dry, ecological, and very efficient. The enhancement of the wettability of the polyester film was necessary for promoting higher adhesion to wood with water-based adhesives. The treatment of polyester films by barrier plasma led to a considerable increase in the surface free energy of the film and subsequently an increase in the peel strength of the adhesive joint of PES film-oak wood with polyurethane adhesive.

In the courses of studies on ellagitannin changes during oak wood toasting, two C-glycosidic ellagitannins were isolated from the french oak wood for the first time. These two compounds exhibited [M−H]− ion peak at m/z 1055.0631 (compound A) and at m/z 1011.0756 (compound B). A compound is named Castacrenin E and is produced by Castacrenin D oxidation. Castacrenin D is a vescalagin with an additional aromating ring to the C-1 through a C-C bond. These compounds are not only found under laboratory conditions but also in commercial oak wood representing different toasting methods and sizes. Their levels are conditioned by oak wood dimensions and toasting degree. The wood pieces with the smallest size present almost two times more compounds A and B. Moreover, the compound B is the only compound to be present in medium toasting temperatures of the smallest wood pieces. Both of them can influence either astringency sensation or bitterness taste.

The sensorial evaluation of Chenin blanc wine produced with different types of oak wood treatments over time has not been investigated before. The main aim of this study was to assess the sensory profile, using a trained panel, of a South African Chenin blanc wine fermented and matured in old barrels, three types of new oak barrels, two types of oak staves as well as a stainless steel tank over time, which has not been done before. Results indicate mainly separation between the stainless-steel tank/old barrel treatments from the stave and new barrel treatments, with separation between the latter two treatments also being found. More fruity descriptors were used in the stainless-steel tank and old barrel treatments, with oak-related descriptors being used in the stave and new barrel treatments. Separation between among the new barrel and stave treatments were also noted, which was still reflected during bottle maturation. These results indicate that winemakers need to take cognizance of the sensorial differences induced by barrel and stave maturation in white wines and how these evolve over time.

The buffer action of certain wood species can intensely affect the curing and hardening of some thermosetting wood adhesives. The present article presents a quantification of such buffering effects, determined under controlled conditions, in various wood species. The buffer capacity of oak has been found to be rather extreme and is likely to affect quite heavily the ability of urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) wood panel adhesives in industrial operations. A variation of the buffer capacity of furnishes containing between 0% and 30% oak chips has been investigated. This was correlated with the internal bond (IB) strength of MUF bonded laboratory particleboards. The wood mixture buffering capacity increases with the oak content, while the panel IB strength decreases.

The interaction of water and oak wood is common in outdoor expositions and will remain a probable occurrence in the future. New insights into the recognition of a cell wall saturation limit are presented by a double-weighing method at 20 °C. The cell wall saturation limit, as the property of thermally modified oak wood, is significantly influenced by different treatment temperatures (20, 160, 180, 210 and 240 °C) on a 5% alpha level. A significantly higher equilibrium moisture content was reached by thermally modified oak wood at a temperature of 20 °C and relative humidity of 65% after its equilibrium in the water-in-reservoir. Moreover, the results are used in the treatment of woodchips to produce cellulose or decomposition of thermally modified wood to its basic chemical components. The investigated properties of cellulose revealed its relationship with water. The number of water molecules bonded to a cellulose chain was correlated with other measured compositions: average molecular weight, total crystalline index, lateral order index and polydispersity index. Analyses showed that there was a strong negative correlation between lateral order index and average molecular weight. The same was true between total crystalline index and average molecular weight. The rest of the properties were positively correlated with the number of water molecules bonded to glucopyranose. The results revealed the possible regeneration of a wood sorption ability after heat treatment and the stability of cellulose in such process.

The aim of this study was to examine certain properties of sessile oak wood (Quercus petraea (Matt.) Liebl.) with frost cracks, such as density (ρ), modulus of rupture (MOR), modulus of elasticity (MOE), and compressive strength in all anatomical directions and to compare it with control trees without frost cracks. Oak with frost cracks had a higher wood density (ρ = 765 kg × m−3) than the control (ρ = 650 kg × m−3). However, despite its lower density, the control oak was characterized by noticeably better mechanical parameters, with the exception of the compressive strength in radial and tangential directions. Differences in mechanical parameters reached up to 26%. The tests were performed on wood taken from trees with frost cracks that formed over 10 years to several decades ago. Frost cracks can render wood vulnerable to fungi growth, which leads to rotting and discoloration. Differences in strength were found on samples with no visible signs of decay, as they were cut at a distance from the crack. Nonetheless, the observed differences in strength allowed us to conclude that the shreds of fungi, as well as decay, may occur in the entire volume of the frost-damaged log. Such wood is, therefore, of a lower quality than that made of logs without any frost damage. Trees with frost cracks should be progressively be felled during the periodic intermediate cutting, as their wood quality may systematically deteriorate over the years.

Thermal modification of wood causes chemical changes that significantly affect the physical, mechanical and biological properties of wood; thus, it is essential to investigate these changes for better utilization of products. Fourier transform infrared spectroscopy and size exclusion chromatography were used for evaluation of chemical changes at thermal treatment of oak wood. Thermal modification was applied according to Thermowood process at the temperatures of 160, 180 and 210 °C, respectively. The results showed that hemicelluloses are less thermally stable than cellulose. Chains of polysaccharides split to shorter ones leading to a decrease of the degree of polymerization and an increase of polydispersity. At the highest temperature of the treatment (210 °C), also crosslinking reactions take place. At lower temperatures degradation reactions of lignin predominate, higher temperatures cause mainly condensation reactions and a molecular weight increase. Chemical changes in main components of thermally modified wood mainly affect its mechanical properties, which should be considered into account especially when designing various timber constructions.

Three different broadleaf Mediterranean forests, each characterized by the dominance of Castanea sativa, Quercus cerris, and Fagus sylvatica, respectively, were intensively surveyed over 3 consecutive years to record a list of macrofungi. A total of 5,065 sporomata and 300 species (seven Ascomycota and 293 Basidiomycota) belonging to 18 orders, 59 families, and 117 genera were recorded. The ecology, community composition, and geographic distribution of the identified species are discussed and new records for Italy are also provided.

Changes in surface material characteristics can significantly affect the adhesion and overall life of coatings on wood. In order to increase the durability of transparent exterior coatings, it is possible to use the surface modification of wood with UV-stabilizing substances. In this work, selected types of surface modifications using benzotriazoles, HALS, ZnO and TiO2 nanoparticles, and their combinations were applied to oak wood (Quercus robur, L.). On such modified surfaces, the surface free energy, roughness, and contact wetting angle with three selected types of exterior transparent coatings were subsequently determined. An oil-based coating, waterborne acrylic thick layer coating, and thin-layer synthetic coating were tested and interaction with the aforementioned surface modifications was investigated after 6 weeks of accelerated artificial weathering. The results of changes in the initially measured surface characteristics of the modified oak wood were compared to the real results of degradation of coatings after artificial accelerated weathering. The positive effect of surface modification, in particular the mixture of benzotriazoles, HALS, and ZnO nanoparticles on all kinds of coatings was proven, and the best results were observed in thick-film waterborne acrylic coating. The changes in the measured surface characteristics corresponded to the observed durability of the coatings only when measured by wetting using drops of the tested coatings.

Heat treatment changes some physical, mechanical, and chemical properties of wood. Inorganic borates have been used as wood preservatives for many years. The aim of this study was to investigate the effects of impregnation chemicals on some mechanical properties (bending strength (MOR), modulus of elasticity (MOE), tensile strength parallel to the grain (TS), compression strength parallel to the grain (CS), and shear strength parallel to the grain (SS)) of heat-treated oak (Quercus petraea Liebl.). For this purpose, the oak wood specimens were impregnated with 5% aqueous solution of boric acid (BA) and borax (BX). Then specimens were heat-treated at 160, 190, and 220 °C for 2 and 4 h. According to the results of the study, borax retention value was higher than boric acid. The bending strength, modulus of elasticity in bending, tensile strength parallel to the grain, and shear strength parallel to the grain decreased due to heat treatment. The highest mechanical strength losses were determined in samples heat treated at 220 °C for 4 h. Generally the mechanical strength losses of samples impregnated with borax were lower than non-impregnated controls and specimens impregnated with boric acid.

This paper studies the influence of ammonia gas on wood color changes in response to an increasing demand for dark colored wood specimens. The darker wood color in ammonia fuming is accomplished through chemical reactions between ammonia gas and wood compounds. We exposed oak, maple, spruce, and larch wood samples to ammonia gas for 16 days. During fuming, the color changes were studied using CIE L*a*b* parameters. After fuming, the changes in extractives content, tannin, and nitrogen content were analyzed. The chemical changes of wood and residues of wood extractives after fuming were analyzed by FTIR spectroscopy. Oak wood reacted intensively with ammonia gas in a very short time, and the darkening was prominent for all the investigated wood species. It was established that tannin had no major influence on color changes of maple and larch wood in the ammonia-fuming process. The FTIR spectra of fumed wood indicated involvement of carbonyl groups, and the FTIR spectra of wood extractives indicated involvement of carbonyl, aromatic, and alcohol groups in reaction with ammonia gas.

Our study is dealing with the determination of the origin of oenological tannins using the modified OIV procedure. The method is based on HPLC analyses of proanthocyanidol content (catechin, epicatechin, epigallocatechin, epicatechin-3-O-gallate and epigallocatechin-3-O-gallate) after thioacidolysis - thiolytic cleavage of the flavonol intermonomer linkages in proanthocyanidols under heat in an acid medium. The purpose of the study was to differentiate oenological tannins gained from Quebracho cortex and tannins extracted from oak wood. As the results show, both groups of tannins do not produce any flavan-3-ols after thioacidolysis, but they show specific peaks, which enable determination of their origin.doi:10.5219/202

The common method to impregnate wood with polyethylene glycol (PEG) is to store the samples for several weeks in aqueous PEG-solution, allowing for diffusion of PEG into the wood. As this method is poorly suited for industrial application, an alternative approach based on vacuum-pressure treatment is evaluated in the present study. Using European oak wood and three variants of PEG, including silane-functionalized PEG, impregnation experiments at different PEG concentrations were performed. Significant uptake of PEG resulted in clearly altered wood-water relations and improved dimensional stability of oak wood. These results are discussed in terms of stability in humid and aqueous environments, and in terms of effects of the anatomy of oak wood on differences in dimensional stabilization observed along the radial and tangential anatomical directions, respectively. While both of the PEG variants perform better with an anti-shrinkage efficiency of up to 80%, the PEG-silane variant performs less effectively in this respect; however PEG-silane is clearly predominant in case of water extraction.

The freshly distilled wine spirit has a high concentration of ethanol and many volatile compounds, but is devoid of phenolic compounds other than volatile phenols. Therefore, an ageing period in the wooden barrel is required to attain sensory fullness and high quality. During this process, several phenomena take place, namely the release of low molecular weight phenolic compounds and tannins from the wood into the wine spirit. Research conducted over the last decades shows that they play a decisive role on the physicochemical characteristics and relevant sensory properties of the beverage. Their contribution to the antioxidant activity has also been emphasized. Besides, some studies show the modulating effect of the ageing technology, involving different factors such as the barrel features (including the wood botanical species, those imparted by the cooperage technology, and the barrel size), the cellar conditions, and the operations performed, on the phenolic composition and related properties of the aged wine spirit. This review aims to summarize the main findings on this topic, taking into account two featured barrel characteristics—the botanical species of the wood and the toasting level.

L'élevage des vins en barriques modifie profondément leur expression aromatique. L'étude par chromatographie en phase gazeuse et spectrométrie de masse permet d'identifier plusieurs substances volatiles appartenant à la fraction phénolique des arômes. Les vins rouges présentent naturellement une composition complexe en phénols volatils alors que celle des vins blancs est plus simple. L'élevage sous bois entraîne une augmentation notable des phénols déjà présents ainsi que l'apparition de molécules spécifiques au bois dechêne brûlé. L'interaction des levures et des bactéries avec le bois est mise en évidence. Les vins rouges se caractérisent par une présence parfois abondante d'éthyl phénols, les vins blancs qui ne subissent pas la fermentation malolactique s'en différencient par l'abondancede vinyl phénols. L'étude sensorielle de chaque substance permet de démontrer le rôle négligeable de certaines : furfural, méthyl-5-furfural, alcool furfurylique et le rôle exceptionnel joué par d'autres : cis et trans β-méthyl-γ-octalactone, vanilline et dans certains cas éthyl-4-phénol et éthyl-4-gaïacol. +++ Wood storage of wines changes profondly their aromatic expression. Several volatile substances from wines and oak woods phenolic fraction of aroma are identified by gas chromatography and mass spectrometry. Wood storage increases natural phenols concentration. Simultaneously specific burned wood molecules appear. Yeast and bacterial interaction with wood is demonstrated. Ethyl phenols are characteristic of red wines and vinyl phenols of white wines without malolactic fermentation. The sensorial analysis of each substance demonstrates the negligible intervention in wine aroma of furfural, 5-methyl-furfural, and furfuryl alcohol, and the important participation of cis and trans β-methyl-γ-octalactone, vanilin 4-ethyl-phenol and 4-ethyl gaïacol.

La scopolétine est un composé phénolique du bois de chêne, présent à l'état de traces dans le raisin. La conservation des vins en barriques entraîne une dissolution progressive de cette substance dans le milieu. Pendant la période d'élevage, l'évolution de cette dissolution suit un rythme analogue à la libération dans les vins d'aldéhydes aromatiques. Pour une même durée d'élevage les vins conservés en barriques neuves sont plus riches en scopolétine et en aldéhydes aromatiques que ceux conservés en barriques plus âgées. +++ Scopoletin is a phenolic compound of oak wood, only traces are present in grapes. Wine storage in oak barrels induces a gradual dissolution of this compound in the medium. During storage period, this dissolution follows the same variations as aromatic aldehydes concentrations. For the same storage time, wines in new barrels have higher scopoletin and aromatic aldehydes concentrations than wines in old barrels.