Oak heartwood usually darkens during and after drying. This darkening can be heterogeneous, leaving non-colored areas in the wood board. These light discolorations have been linked to heterogeneous distribution of tannins, but compelling evidence on the microscale is lacking. In this study Raman and fluorescence microscopy revealed precipitations of crystalline ellagic acid, especially in the ray cells but also in lumina, cell corners and cell walls in the non-colored areas (NCA), which also had higher density. In these denser areas free water is longer present during drying and leads to accumulation of hydrolyzed tannins. When eventually falling dry, these tannins precipitate irreversible as non-colored ellagic acid and are not available for chemical reactions leading to darkening of the wood. Therefore, pronounced density fluctuations in wood boards require adjusting the drying and processing parameters so that water domains and ellagic acid precipitations are avoided during drying.
This paper is dedicated to Prof. Adya Singh who spent the last months of his long and fruitful scientific carrier with us. We are very grateful that he chose our working group for his last stay abroad and we profited a lot from his knowledge and insight. Besides that, we also enjoyed the time off-duty with him and wish him a beautiful retirement in New Zealand.
Funding source: H2020 European Research Council
Award Identifier / Grant number: European Union’s Horizon 2020 research and innov
Funding source: Austrian Science Fund
Award Identifier / Grant number: START Project (Y-728-B16)
Funding source: Austrian Academy of Sciences
Award Identifier / Grant number: DOC-Fellowship (24763)
We thank the whole bionami research group for helpful comments (www.bionami.at) and Wood K plus – Competence Centre for Wood Composites and Wood Chemistry (https://www.wood-kplus.at/de) for the collaboration. We especially thank Tayebeh Saghaei for the fruitful scientific discussions.
Author contributions: M.F. carried out Raman microscopic imaging, stainings, density measurements, interpreted the data and wrote the manuscript. N.G. had the idea for the manuscript, conducted analysis of the Raman images and assisted in manuscript writing. N.X. conducted the fluorescence microscopic experiments. C.P. carried out the drying experiments. M.L. conducted the HPLC measurements. C.H. assisted in data interpretation and manuscript writing. P.B. measured Raman, IR and UV-spectra of all reference compounds, interpreted the data and wrote the manuscript.
Research funding: This work is supported by a fellowship of the Austrian Academy of Science (ÖAW) , the START Project [Y-728-B16] from the Austrian Science Fund (FWF) and from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program grant agreement no. 681885.
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
Alfei, S., Turrini, F., Catena, S., Zunin, P., Parodi, B., Zuccari, G., Pittaluga, A.M., and Boggia, R. (2019). Preparation of ellagic acid micro and nano formulations with amazingly increased water solubility by its entrapment in pectin or non-PAMAM dendrimers suitable for clinical applications. New J. Chem. 43: 2438–2448, https://doi.org/10.1039/c8nj05657a.Search in Google Scholar
Almeida, G. and Hernández, R. (2006). Changes in physical properties of yellow birch below and above the fiber saturation point. Wood Fiber Sci. 38: 83.Search in Google Scholar
Belt, T., Keplinger, T., Hänninen, T., and Rautkari, L. (2017). Cellular level distributions of Scots pine heartwood and knot heartwood extractives revealed by Raman spectroscopy imaging. Ind. Crop. Prod. 108: 327–335, https://doi.org/10.1016/j.indcrop.2017.06.056.Search in Google Scholar
Bock, P. and Gierlinger, N. (2019). Infrared and Raman spectra of lignin substructures: coniferyl alcohol, abietin, and coniferyl aldehyde. J. Raman Spectrosc. 50: 778–792.10.1002/jrs.5588Search in Google Scholar PubMed PubMed Central
Bock, P., Nousiainen, P., Elder, T., Blaukopf, M., Amer, H., Zirbs, R., Potthast, A., and Gierlinger, N. (2020). Infrared and Raman spectra of lignin substructures: dibenzodioxocin. J. Raman Spectrosc. 51: 422–431, https://doi.org/10.1002/jrs.5808.Search in Google Scholar
Brunner, R. (1999). Vakuumtrocknung im wirtschaftlichkeitsvergleich. Teil. Holz-Zentralblatt 57: 874–875.Search in Google Scholar
Charrier, B., Haluk, J.P., and Janin, G. (1992a). Prevention of brown discoloration in European oakwood occurring during kiln drying by a vacuum process: colorimetric comparative study with a traditional process. Holz als Roh- Werkst. 50: 433–437, https://doi.org/10.1007/bf02662781.Search in Google Scholar
Charrier, B., Marques, M., and Haluk, J.P. (1992b). HPLC analysis of gallic and ellagic acids in European oakwood (Quercus robur L.) and eucalyptus (Eucalyptus globulus). Holzforschung 46: 87, https://doi.org/10.1515/hfsg.1918.104.22.168.Search in Google Scholar
Charrier, B., Haluk, J.P., and Metche, M. (1995). Characterization of European oakwood constituents acting in the brown discoloration during kiln drying. Holzforschung 49: 168–172, https://doi.org/10.1515/hfsg.1922.214.171.124.Search in Google Scholar
Donaldson, L.A., Singh, A., Raymond, L., Hill, S., and Schmitt, U. (2019). Extractive distribution in Pseudotsuga menziesii: effects on cell wall porosity in sapwood and heartwood. IAWA J. 40: 721–740, https://doi.org/10.1163/22941932-40190248.Search in Google Scholar
Felhofer, M., Prats-Mateu, B., Bock, P., and Gierlinger, N. (2018). Antifungal stilbene impregnation: transport and distribution on the micron-level. Tree Physiol. 38: 1526–1537, https://doi.org/10.1093/treephys/tpy073.Search in Google Scholar
Fortuin, G., Welling, J., Hesse, C., and Brückner, G. (1988a). Verfärbung von Eichenschnittholz bei der Trocknung (a). Holz-Zentralblatt 114: 1606–1608.Search in Google Scholar
Fortuin, G., Welling, J., Hesse, C., and Brückner, G. (1988b). Verfärbung von Eichenschnittholz bei der Trocknung (b). Holz-Zentrallblatt 114: 1621–1622.Search in Google Scholar
Fromm, J.H., Sautter, I., Matthies, D., Kremer, J., Schumacher, P., and Ganter, C. (2001). Xylem water content and wood density in spruce and oak trees detected by high-resolution computed tomography. Plant Physiol. 127: 416–425, https://doi.org/10.1104/pp.010194.Search in Google Scholar
Hejazifar, M., Earle, M., Seddon, K.R., Weber, S., Zirbs, R., and Bica, K. (2016). Ionic liquid-based microemulsions in catalysis. J. Org. Chem. 81: 12332–12339, doi:https://doi.org/10.1021/acs.joc.6b02165.Search in Google Scholar
Hernández, R. and Cáceres, C. (2010). Magnetic resonance microimaging of liquid water distribution in sugar maple wood below fiber saturation point. Wood Fiber Sci. 42: 259–272.Search in Google Scholar
Higuchi, T. (2012). Biosynthesis and biodegradation of wood components. Elsevier Science, Amsterdam. https://doi.org/10.1016/B978-0-12-347880-1.X5001-6.Search in Google Scholar
Kisseloff, P. (1993). Über den Entstehungsmechanismus von Braunverfärbungen bei der Trocknung von Eichenholz. Holz-Zentralblatt 136: 2165–2166.Search in Google Scholar
Klumpers, J., Scalbert, A., and Janin, G. (1994). Ellagitannins in European oak wood: polymerization during wood ageing. Phytochemistry 36: 1249–1252, https://doi.org/10.1016/s0031-9422(00)89646-6.Search in Google Scholar
Koch, G. and Skarvelis, M. (2007). Discoloration of wood during drying. In: Perré, P. (Ed.). Fundamentals of wood drying. COST E-15: 1-22 AR BO. LOR, France.Search in Google Scholar
Mayer, W., Gabler, W., Riester, A., and Korger, H. (1967). Die isolierung von castalagin, vescalagin, castalin und vescalin. Liebigs Ann. Chem. 707: 177–181, https://doi.org/10.1002/jlac.19677070125.Search in Google Scholar
Menon, R., MacKay, A., Hailey, J., Bloom, M., Burgess, A., and Swanson, J. (1987). An NMR determination of the physiological water distribution in wood during drying. J. Appl. Polym. Sci. 33: 1141–1155, https://doi.org/10.1002/app.1987.070330408.Search in Google Scholar
Miranda, I., Sousa, V., Ferreira, J., and Pereira, H. (2017). Chemical characterization and extractives composition of heartwood and sapwood from Quercus faginea. PLoS One 12: e0179268, https://doi.org/10.1371/journal.pone.0179268.Search in Google Scholar
Okuda, T. (2005). Systematics and health effects of chemically distinct tannins in medicinal plants. Phytochemistry 66: 2012–2031, https://doi.org/10.1016/j.phytochem.2005.04.023.Search in Google Scholar
Passarini, L., Malveau, C., and Hernández, R.E. (2014). Water state study of wood structure of four hardwoods below fiber saturation point with nuclear magnetic resonance. Wood Fiber Sci. 46: 480–488.Search in Google Scholar
Peng, S., Scalbert, A., and Monties, B. (1991). Insoluble ellagitannins in Castanea sativa and Quercus petraea woods. Phytochemistry 30: 775–778, https://doi.org/10.1016/0031-9422(91)85250-4.Search in Google Scholar
Perré, P. (2007). Fundamentals of wood drying. AR BO. LOR Nancy.Search in Google Scholar
Plötze, M. and Niemz, P. (2011). Porosity and pore size distribution of different wood types as determined by mercury intrusion porosimetry. Eur. J. Wood Prod. 69: 649–657, https://doi.org/10.1007/s00107-010-0504-0.Search in Google Scholar
Puech, J.-L., Feuillat, F., and Mosedale, J. (1999). The tannins of oak heartwood: structure, properties, and their influence on wine flavor. Am. J. Enol. Vitic. 50: 469–478.10.5344/ajev.19126.96.36.1999Search in Google Scholar
Quideau, S., Jourdes, M., Saucier, C., Glories, Y., Pardon, P., and Baudry, C. (2003). DNA topoisomerase inhibitor acutissimin A and other flavano-ellagitannins in red wine. Angew. Chem. 115: 6194–6196, https://doi.org/10.1002/ange.200352089.Search in Google Scholar
Ramage, M.H., Burridge, H., Busse-Wicher, M., Fereday, G., Reynolds, T., Shah, D.U., Wu, G., Yu, L., Fleming, P., Densley-Tingley, D., et al.. (2017). The wood from the trees: the use of timber in construction. Renew. Sustain. Energy Rev. 68: 333–359, https://doi.org/10.1016/j.rser.2016.09.107.Search in Google Scholar
Segmehl, J.S., Lauria, A., Keplinger, T., Berg, J.K., and Burgert, I. (2018). Tracking of short distance transport pathways in biological tissues by ultra-small nanoparticles. Front. Chem. 6: 28, https://doi.org/10.3389/fchem.2018.00028.Search in Google Scholar
Sukor, N.F., Jusoh, R., Kamarudin, N.S., Abdul Halim, N.A., Sulaiman, A.Z., and Abdullah, S.B. (2020). Synergistic effect of probe sonication and ionic liquid for extraction of phenolic acids from oak galls. Ultrason. Sonochem. 62: 104876, https://doi.org/10.1016/j.ultsonch.2019.104876.Search in Google Scholar
Ursache, R., Andersen, T.G., Marhavý, P., and Geldner, N. (2018). A protocol for combining fluorescent proteins with histological stains for diverse cell wall components. Plant J. 93: 399–412.10.1111/tpj.13784Search in Google Scholar
Viriot, C., Scalbert, A., Lapierre, C., and Moutounet, M. (1993). Ellagitannins and lignins in aging of spirits in oak barrels. J. Agric. Food Chem. 41: 1872–1879, https://doi.org/10.1021/jf00035a013.Search in Google Scholar
Viriot, C., Scalbert, A., du Penhoat, C.L.H., and Moutounet, M. (1994). Ellagitannins in woods of sessile oak and sweet chestnut dimerization and hydrolysis during wood ageing. Phytochemistry 36: 1253–1260, https://doi.org/10.1016/s0031-9422(00)89647-8.Search in Google Scholar
Vivas, N., Bourden-Nonier, M., de Gaulejac, N.V., Mouche, C., and Rossy, C. (2020). Origin and characterisation of the extractable color of oak heartwood used for ageing spirits. J. Wood Sci. 66: 21, https://doi.org/10.1186/s10086-020-01866-3.Search in Google Scholar
Wassipaul, F. and Fellner, J. (1992). Eichenverfärbung bei der Trocknung mit niederen Temperaturen. Holzforsch. Holzverwert. 44: 86–88.Search in Google Scholar
Wassipaul, F., Vanek, M., and Fellner, J. (1987). Verfärbung von Eichenschnittholz bei der künstlichen Holztrocknung. Holzforsch. Holzverwert. 39: 1–5.Search in Google Scholar
Wegener, G. and Fengel, D. (1988). Zum Stand der chemischen und mikroskopischen Untersuchungen an trocknungsverfärbtren Eichenschnittholz. Holz-Zentralblatt 114: 2238–2241.Search in Google Scholar
Welling, J. and Wöstheinrich, A. (1995). Reduzierung von Verfärbungen durch Heißdampf-Vakuumtrocknung. Holz-Zentralblatt 8: 145–150.Search in Google Scholar
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