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Hot water extraction of Norway spruce (Picea abies [Karst.]) bark: analyses of the influence of bark aging and process parameters on the extract composition

Bianchi, Sauro ; Koch, Gerald ; Janzon, Ron ; Mayer, Ingo ; Saake, Bodo ; Pichelin, Frédéric

In: Holzforschung, 2016, vol. 70, no. 7, p. 619-631

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    Title
    • Hot water extraction of Norway spruce (Picea abies [Karst.]) bark: analyses of the influence of bark aging and process parameters on the extract composition
    Author
    • Bianchi, Sauro. Bern University of Applied Science, Architecture Wood and Civil Engineering, Solothurnstrasse 102, 2502 Biel/Bienne, Switzerland
    • Koch, Gerald. Thünen Institute (TI), Institute of Wood Research, Leuschnerstrasse 91, 21031 Hamburg, Germany
    • Janzon, Ron. University of Hamburg, Chemical Wood Technology, Leuschnerstrasse 91b, 21031 Hamburg, Germany
    • Mayer, Ingo. Bern University of Applied Science, Architecture Wood and Civil Engineering, Solothurnstrasse 102, 2502 Biel/Bienne, Switzerland
    • Saake, Bodo. University of Hamburg, Chemical Wood Technology, Leuschnerstrasse 91b, 21031 Hamburg, Germany
    • Pichelin, Frédéric. Bern University of Applied Science, Architecture Wood and Civil Engineering, Solothurnstrasse 102, 2502 Biel/Bienne, Switzerland
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:326351
    Summary
    The hot water (HW) extraction of Norway spruce (Picea abies [Karst.]) delivers condensed tannins and considerable amounts of other compounds. Yield and composition of the HW extracts were investigated as a function of natural weathering for up to 15 months. Total phenol monomers and oligomers were detected by Folin-Ciocaltau assay after fractionation by solid phase extraction (SPE). Procyanidins (PC) were determined by HPLC-UV after acid thiolysis and carbohydrates by HPLC combined with acid hydrolysis. Topochemistry of the bark before and after extraction was investigated by UV-microspectrometry (UMSP) and non-extractable PC analyzed by direct thiolysis on the bark. The influence of the parameters on the yield and composition of the extracts were evaluated, such as the extraction temperature, time and the addition of sodium sulfate and urea. Prolonged weathering resulted in a considerable decrease of the total extraction yield, partly because of leaching of phenolic monomers, mono- and oligosaccharides. The yield of phenolic oligomers also decreased at a moderate rate, while the yield of polysaccharides (pectins) was almost stable. Non-extractable and non-leachable compounds deposited in the cell lumens represent the majority of the phenolic extractives in spruce bark. Sequential extractions performed at increasing temperature proved to be a suitable method for the recovery of tannin-rich extracts.