Colorimetric behavior and seasonal characteristic of xylem sap obtained by mechanical compression from silver birch (Betula pendula)

A. Yamamoto, A. Rohumaa, E. Kontturi (Corresponding Author), M. Hughes, P. Saranpää, Martina Blomster Andberg, T. Vuorinen

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)


This study investigated the color development in fresh birch xylem sap (Betula pendula) squeezed by mechanical compression, which was not seen in birch exudate and squeezed spruce sap. Altering the pH of the colored xylem sap demonstrated distinctive patterns of light absorption bands which suggested the formation of quinonoid intermediates by the enzymatic activity of polyphenol oxidases (PPO). Comparison with other PPOs by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) suggested the presence of the enzyme in the sap. The major phenol which acts as a substrate for PPO was identified as (−)-epicatechin. Inhibition of the color development was also attempted using Na2SO3, ethylenediaminetetraacetic acid (EDTA), and N2 gas. The results showed that Na2SO3 was the most effective inhibitor. Knowledge on the differences between squeezed and exuded sap is important because squeezing can be envisaged as a pretreatment step for any process—such as a biorefinery—that utilizes biomass and has the advantage of utilizing trees that have recently been felled.
Original languageEnglish
Pages (from-to)1075-1082
Number of pages7
JournalACS Sustainable Chemistry & Engineering
Issue number9
Publication statusPublished - 2013
MoE publication typeA1 Journal article-refereed



  • birch sap
  • carbohydrates
  • mechanical compression
  • seasonal variation
  • UV-vis spectroscopy

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