Abstract
Considering the toxicity of the impurities of synthesized anthraquinone, this study clarified new catalytic compounds for kraft cooking with improved carbohydrate yield and delignification and less mutagenicity, which are important for ensuring the safety of paper products in contact with food. The 2-methylanthraquinone contents of teak (Tectona grandis) woods were 0.18–0.21%. Acetone extracts containing 2-methylanthraquinone from Myanmar and Indonesia teak woods as additives improved lignin removal during kraft cooking of eucalyptus wood, which resulted in kappa numbers that were 2.2–6.0 points lower than the absence of additive. Myanmar extracts and 2-methylanthraquinone improved carbohydrate yield in pulps with 1.7–2.2% yield gains. Indonesia extracts contained more deoxylapachol and its isomer than 2-methylanthraquinone. The residual content of 2-methylanthraquinone in the kraft pulp was trace. Although Ames tests showed that the Indonesia and Myanmar extracts were mutagenic to Salmonella typhimurium, 2-methylanthraquinone was not. The kraft pulp obtained with the additives should be safe for food-packaging applications, and the addition of 0.03% 2-methylanthraquinone to kraft cooking saves forest resources and fossil energy in industries requiring increased pulp yield.
Highlights
One of the first applications of anthraquinone (AQ) (9,10-anthracenedione) or AQ derivatives as an additive in alkaline cooking was reported in 1972 by Bach and Fiehn [1]
The 2-MAQ content determined from the calibration curve was 0.18% based on the wood weight for Indonesia teak wood (Table 2) compared with 0.21% in Myanmar teak wood [17]
Extracts of Myanmar and Indonesia teak woods containing 2-MAQ improved kappa number decreases by removing lignin during kraft cooking compared with the absence of an additive
Summary
One of the first applications of anthraquinone (AQ) (9,10-anthracenedione) or AQ derivatives as an additive in alkaline cooking was reported in 1972 by Bach and Fiehn [1]. AQ is known to increase the rate of delignification; reduce cooking time, temperature, or chemical charge; increase pulp yield. The AHQ is oxidized back to AQ via a reaction with lignin, reducing the active site (ß-O-4) in lignin during alkaline cooking [3]. Most kraft pulp mills in Japan use soluble anthraquinone (SAQ) at doses of 0.02–0.1% (200–1000 mg/kg) based on oven-dried wood weight [4]. The US Food and Drug Administration (FDA) allows an AQ charge at the level of 0.1% on oven-dried wood as an additive during the alkaline cooking of wood material, which is the maximum amount for paper that will contact food [2]
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