The influence of the origin and treatment history of spruce and pine bark on the extraction of tannin

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Title: The influence of the origin and treatment history of spruce and pine bark on the extraction of tannin
Author: Ruuskanen, Miikka
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Forest Sciences
Publisher: Helsingfors universitet
Date: 2017
Language: eng
Thesis level: master's thesis
Discipline: Skoglig ekologi och resurshushållning
Forest Ecology and Management
Metsien ekologia ja käyttö
Abstract: The aim of this thesis was to study how the origin and treatment histories of spruce (Picea abies) and pine (Pinus radiata, Pinus sylvestris) bark influence on the extraction yield of tannin. The bark is produced in large quantities during the debarking process and is considered as waste in traditional forest industry. Bark is mainly used for energy production. In comparison to wood tissue, bark contains more extractives that could have potential for various applications in pharmaceutical industry or bio-based adhesives. Stilbenes, lignans, flavonoids and tannins are typical extractives in wood bark. In this Master’s thesis, the focus is on the extraction of tannins. Bark raw materials were obtained from pulp mills and sawmills. Bark samples were processed as air-dried (drying < 50 °C) or fresh as it is after debarking. Samples were extracted in rotating air bath reactors at 90 °C and 10 % consistency. Eight batches were hot water extracted and five different time points were studied: 40, 60, 80, 100 and 120 minutes. The extracts were analyzed with three UV-spectrophotometric methods: Folin-Ciocalteu assay, UV-280 nm method and Acid-Butanol assay. UV-280 nm method was used in tannin yield calculations. Tannin yield was the highest from air-dried spruce bark from sawmill (5.63 % from original dry bark). The second highest tannin yield (3.33 %) was from air-dried sawmill pine (Pinus radiata) bark extract. Fresh sawmill spruce and pine bark extraction gave 2.59 % and 2.65 % for tannin yield, respectively. The poorest yields came from the pulp mill bark samples. Yields from fresh and air-dried pulp mill spruce barks were 0.41 % and 0.97 %, respectively. In comparison, the tannin yields from fresh and air-dried pulp mill pine (Scots pine) bark were 1.13 % and 1.20 %. Results showed that the tannin yield increased when the extraction time increased. Statistical analysis confirmed that the origin and the treatment have a significant influence on the extraction yield of tannin. The reason for the differences in the extraction yields between barks with different origins are probably related to the different debarking methods. Sawmill bark samples gave a significantly higher tannin yield than samples from pulp mill. In sawmills, logs are debarked as dry in rotary debarker. Drum debarkers are typically being used in pulp and paper mills where water is used in debarking process. Contact with water may leach water-soluble tannins from bark. This is in accordance with the results that bark from sawmill was found to be an optimal raw material for hot water extraction. Further research should focus on optimizing hot water extraction conditions eg. by applications of chemicals.
Subject: Bark
Norway spruce
Scots pine
Radiata pine
pulp mill
rotary debarker
drum debarker
treatment history
hot water extraction
UV-spectrophotometric methods

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