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Licensed Unlicensed Requires Authentication Published by De Gruyter October 11, 2019

Chemical characterisation of polymerised extractives in bleached birch kraft pulp

  • Annika I. Smeds EMAIL logo , Lari Vähäsalo , Jani Rahkila , Patrik C. Eklund and Stefan M. Willför
From the journal Holzforschung


The main aim of this study was to chemically characterise the polymeric fraction of birch pulp extractives. We showed that 70–96% of the material in extracts of fully bleached birch kraft elemental chlorine-free (ECF) pulp from three Finnish mills consists of compounds that are undetectable by conventional gas chromatography (GC) analysis, i.e. high-molar mass (HM) material. There were small variations in the extractive content and composition between the three mills, but the overall trend was the same. The HM material was present mainly in the acetone extracts, and the molar mass was shown to range between ca. 1000 and 10 000 Da. Alkaline hydrolysis of the hexane and acetone extracts released fatty acids (FAs) especially, but also sterols and triterpenoids. The dominating FAs were palmitic and stearic acids. Pyrolysis and thermally assisted hydrolysis and methylation (THM)-GC-mass spectrometry (MS) analyses confirmed that the HM material consists mainly of FA units, and additionally of sterol, triterpenoid and aromatic units. Nuclear magnetic resonance (NMR) analysis further confirmed the presence of FAs containing aromatic groups, but also glycerol units. The FA chains seemed to be linked to each other by ester linkages mainly, although ether linkages were also present. The FA oligomers and polymers may have a suberin-like structure.


This work was part of the activities at the Johan Gadolin Process Chemistry Center at Åbo Akademi University.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: None declared.

  3. Employment or leadership: None declared.

  4. Honorarium: None declared.


Bergelin, E., Holmbom, B. (2003) Deresination of birch kraft pulp in bleaching. J. Pulp Paper Sci. 29:29–34.Search in Google Scholar

Bergelin, E., von Schoultz, S., Hemming, J., Holmbom, B. (2003) Evaluation of methods for extraction and analysis of wood resin in chemical pulp. Nord. Pulp Paper Res. J. 19:129–133.10.3183/npprj-2003-18-02-p129-133Search in Google Scholar

Bergelin, E., Möller, R., Holmbom, B. (2005) Analysis of pitch and deposit samples in kraft pulp production. Pap. Puu 87:1–5.Search in Google Scholar

Bernards, M.A. (2002) Demystifying suberin. Can. J. Bot. 80:227–240.10.1139/b02-017Search in Google Scholar

Björklund Jansson, M. (2005) Birch extractives in kraft pulp washing. Report no. 141, STFI-Packforsk, Stockholm, Sweden.Search in Google Scholar

Ekman, R. (1983a) The suberin monomers and triterpenoids from the outer bark of Betula verrucosa Ehrh. Holzforschung 37:205–211.10.1515/hfsg.1983.37.4.205Search in Google Scholar

Ekman, R. (1983b) Lipophilic extractives of the inner bark of birch, Betula verrucosa Ehrh. Finn. Chem. Lett. 162–165.Search in Google Scholar

Ekman, R., Holmbom, B. (2000) The chemistry of wood resin. In: Pitch Control, Wood Resin and Deresination. Eds. Back, E.L., Allen, L.H. TAPPI Press, Atlanta, GA, USA. pp. 37–76.Search in Google Scholar

Koskinen, K. (1999) Wood handling applications. In: Papermaking Science and Technology, Book 6A: Chemical Pulping. Eds. Gullichsen, J., Fagerholm, C.-J. Fapet Oy, Helsinki, Finland.Search in Google Scholar

Ohtani, Y., Shigemoto, T., Okagawa, A. (1986) Chemical aspects of pitch deposits in kraft pulping of hardwoods in Japanese mills. Appita J. 39:301–306.Search in Google Scholar

Örså, F., Holmbom, B. (1994) A convenient method for the determination of wood extractives in paper process waters and effluents. J. Pulp Paper Sci. 20:J361–J366.Search in Google Scholar

Sitholé, B., Lapierre, L., Watanabe, C. (2013) A study of polymerization of aspen (Populus) wood lipophilic extractives by SEC and Py-GC-MS. Appita J. 66:59–65.Search in Google Scholar

Smeds, A.I., Eklund, P.C., Monogioudi, E., Willför, S.M. (2012) Chemical characterization of polymerized products formed in the reactions of matairesinol and pinoresinol with the stable radical 2,2-diphenyl-1-picrylhydrazyl. Holzforschung 66:283–294.10.1515/hf.2011.151Search in Google Scholar

Smeds, A.I., Eklund, P.C., Willför, S.M. (2016) Chemical characterization of high-molar-mass fractions in a Norway spruce knotwood ethanol extract. Phytochemistry 130:207–217.10.1016/j.phytochem.2016.05.006Search in Google Scholar PubMed

Smeds, A.I., Eklund, P.C., Willför, S.M. (2018) Characterization of high-molar-mass fractions in a Scots pine (Pinus sylvestris L.) knotwood hydrophilic extract. Holzforschung 72:201–213.10.1515/hf-2017-0079Search in Google Scholar

Zheng, H., Uhing, M.C., Cosper, D.R. (2002) A new method of analyzing pitch deposits in pulp and paper processes. J. Pulp Paper Sci. 28:204–210.Search in Google Scholar

Received: 2019-03-14
Accepted: 2019-06-04
Published Online: 2019-10-11
Published in Print: 2019-10-25

©2019 Walter de Gruyter GmbH, Berlin/Boston

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