Significance of Western Hemlock Phenolic Extractives in Pulping and Lumber

Western hemlock contains many brown tannin-like phenolics which may cause brightness problems in pulp and stain problems in lumber. Five phenolics have been isolated from western hemlock. These are conidendron, hydroxymatairesinol, matairesinol, leucocyanidin, and catechin. In this research, catechin was demonstrated to be responsible for brown stain in western hemlock. The evidence was obtained by developing paper chromatograms of sapwood extractive on thick Whatman paper and then using juice expressed from hemlock sapwood by pressure as a detecting reagent. A well-defined brown coloration in the area corresponding to catechin was easily observed after several hours storage in a humidity chamber. The remainder of the chromatogram was essentially colorless. Catechin migrates to the surface of western hemlock sapwood where it accumulates due to evaporation and develops the brown stain upon reaction with air. Low pH substances, reducing agents, strong chelating agents, cysteine, and sodium thioglycollate prevented color development in laboratory experiments but were not effective in the field. High pH conditions should be avoided because color develops rapidly. Catechin is also suspected to cause low brightness in western hemlock pulp.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member