UV light impact on ellagitannins and wood surface colour of European oak (Quercus petraea and Quercus robur)

Zahri, Sofia; Belloncle, Christophe; Charrier, Fatima; Pardon, Patrick; Quideau, Stéphane; Charrier, Bertrand

doi:10.1016/j.apsusc.2006.11.005

Cited by 51 publications

(42 citation statements)

References 18 publications

(22 reference statements)

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“…The degradation of extractives and rapid oxidation of degradation products may act as protection of the main wood components (Nzokou and Kamdem 2006;Chang et al 2010). A different resistance to photodegradation of some extractives was highlighted by Zahri et al (2007), underlining that gallic acid is much more stable than ellagic acid after UV light exposure.…”

Section: Resultsmentioning

confidence: 98%

Colour and chemical changes on photodegraded beech wood with or without red heartwood

et al. 2014

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The focus of this study was to investigate the chemical and colour changes occurring at different exposure times on artificially photo-irradiated surfaces of normal and red heartwood in beech in order to understand the mechanisms that cause the changes and to evaluate the possibility of usages of beech not only for energy production purposes. In this sense, surface colour modifications are of crucial importance to define the commercial value of beech wood. The artificial photo-irradiation of the wood samples was performed in a Solar Box, equipped with an ultraviolet filter that cuts off the spectrum at 280 nm. Reflectance spectrophotometry and Fourier transform infrared (FTIR) spectroscopy were used to assess artificial sunlight influence. The experimental data were statistically treated to evaluate their significance. Colour monitoring revealed that wood surface colour undergoes an important variation due to photo-irradiation, occurring within the first 24-48 h. Moreover, it was found that the chromatic coordinates (L*a*b*) in normal wood and in red heartwood tended to similar values after 504 h. FTIR spectroscopy allowed for investigating the rate of photodegradation of wood surface due to oxidation reactions of wood components. The results were validated by statistical analysis applied both to the colorimetric and spectroscopic data.

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Section: Resultsmentioning

confidence: 98%

Colour and chemical changes on photodegraded beech wood with or without red heartwood

et al. 2014

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“…These are then responsible for the color change of wood. The extractives in wood are also sensitive to light irradiation (Pandey 2005b;Nzokou and Kamdem 2006;Zahri et al 2007;Chang et al 2010;Fan et al 2010). Živković et al (2014) investigated the effect of wavelength on photodegradation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Air Relative Humidity and Temperature on Photodegradation Processes in Beech and Spruce Wood

Tolvaj¹,

Popescu²,

Molnár³

et al. 2015

BioResources

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Spruce and beech samples were irradiated by UV light in humid (100% air humidity) and dry conditions to clarify the effects of vapor on photodegradation. UV-irradiated samples were also soaked in distilled water for comparison. The color change and the IR absorption spectra were measured. The wet condition generated considerably greater discoloration than did the dry condition. The intensity of the color change was higher at elevated temperature (53 °C) than at 32 °C. The results showed that the presence of water as vapor increased the degradation of lignin. The nonconjugated carbonyl groups absorbing around 1760 cm -1 were found not to be stable, and the number of these chemical groups decreased in the presence of vapor when compared against the dry condition. The rising temperature amplified this degradation effect.

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“…Ils peuvent par conséquence produire des composés de discoloration. Dans le cas du chêne, la participation des gallotanins et des éllagitanins a été bien identifiée dans les processus de discoloration (Haluk, Schloegel et Metche, 1991;Charrier, 1992;Koch, 2008;Zahri, 2007). D´après la figure 9, la luminosité est toujours plus forte dans les surfaces en contact avec la source de chaleur.…”

Section: Resultats Et Discussionunclassified

Étude des altérations de la couleur du bois de Chêne lors du séchage sous vide discontinu

Sandoval-Torres¹,

Jomaa²,

Marc³

et al. 2016

MYB

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Une analyse des mécanismes de discoloration du bois de chêne au cours d’un séchage sous vide sur plaques nous a permis de dégager les mécanismes principaux de l´altération de la couleur. Ces mécanismes sont la dégradation des hémicelluloses, l’oxydation des tannins et le dégagement de composants volatiles organiques. Nous avons étudié les altérations du matériau par la mesure de la couleur, le dosage du potentiel antioxydant et l’analyse des surfaces par spectroscopie infrarouge. Différentes conditions de séchage : 46 °C, 61 °C et 70 °C et niveaux de pression 6 kPa - 10 kPa (60 mBar - 100 mBar) ont été appliquées. Malgré la difficulté d’étudier et d’affirmer le rôle des extractibles dans la discoloration du chêne au cours du séchage, nous avons montré des relations entre la température appliquée, les valeurs des potentiels antioxydants et les intensités C=O des spectres FTIR. Par des phénomènes d’oxydation et d’hydrolyse, certains constituants chimiques sont modifiés. En outre, la présence d’eau et d’air accélère la formation d’acides organiques (acide acétique). Ces acides catalysent l’hydrolyse des hémicelluloses. L’augmentation de la saturation et de la luminosité peuvent être liées à la dégradation thermique des extractibles (éllagitanins principalement). Estudio de las alteraciones de color en madera de encino europeo durante el secado a vacío Un análisis de los mecanismos de decoloración de la madera de encino europeo durante un proceso de secado al vacío por contacto ha permitido identificar los principales mecanismos de la alteración del color. Estos mecanismos son la degradación de las hemicelulosas, la oxidación de taninos y la pérdida de compuestos orgánicos volátiles. Se estudiaron las alteraciones del material midiendo los cambios de color, determinando el potencial antioxidante y analizando la superficie del material por espectroscopía infrarroja. Las condiciones de secado aplicadas fueron las siguientes: 46 °C, 61 °C y 70 °C a niveles de presión de 6 kPa - 10 kPa (60 mBar - 100 mBar). A pesar de la dificultad de estudiar y establecer el papel de los extractivos en los cambios de color durante el secado a vacío, en este trabajo se muestra la relación entre la temperatura de secado, los valores de potencial antioxidante y las intensidades de los picos C=O de los espectros. Por medio de mecanismos de oxidación e hidrólisis, ciertos compuestos químicos son modificados. Por otro lado, la presencia de agua y aire aceleran la formación de ácidos orgánicos (ácido acético). Estos ácidos catalizan la hidrólisis de las hemicelulosas. Un aumento de la saturación del color y la luminosidad pueden estar relacionados con la degradación térmica de los extractivos (principalmente de los elagitaninos).

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UV light impact on ellagitannins and wood surface colour of European oak (Quercus petraea and Quercus robur)

Cited by 51 publications

References 18 publications

Colour and chemical changes on photodegraded beech wood with or without red heartwood

Colour and chemical changes on photodegraded beech wood with or without red heartwood

Effects of Air Relative Humidity and Temperature on Photodegradation Processes in Beech and Spruce Wood

Étude des altérations de la couleur du bois de Chêne lors du séchage sous vide discontinu

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