Arabinogalactan from Western Larch Wood

Arabogalactan was obtained from four butt logs of Larix occidentalis using a process involving hot water extraction, vacuum concentration, and spray drying. Extraction was conducted in pilot plant equipment using 25 lbs. of air-dry chips and 100 lbs. of water per charge. Insulation board of commercial quality was prepared from extracted chips. The percent solids in extract increased with extraction time and temperature. The optimum extraction rate occurred at approximately 5 to 10 hours at a temperature of 160?F. Extracts prepared above this temperature are darker in color and have a lower pH. Extractive yields at optimum conditions were about 2.5 percent (solids in the extract). Rate of extraction was increased by either replacing water dilute alcohol solutions as a solvent or by using finely ground wood in the place of chips. Concentration of arabogalactan liquors at atmospheric pressure results in considerable burning and darkening. Satisfactory concentration to 50 percent solids was accomplished under a vacuum of 22 to 24 inches of mercury. Concentrations above 50 percent were difficult to handle. Because of its susceptibility to fungus attack, it was necessary to dry the concentrated syrup. Fifty percent solutions were successfully dried using a small stainless steel, powdered milk spray dryer. Best quality material resulted at inlet air temperatures of 270?-300?F. The spray-dried powder is light buff to tan in color, fine, unctious, non-hygroscopic, and has a bulk density of approximately 24 pcf. The powder has a faint, pleasant and woody odor, and can be stored indefinitely at room temperature and 3-6 percent EMC conditions. It dissolves readily in water to yield an amber solution. Methods to purify the crude arabogalactan powder resulted in a color change from tan to white, improved solubility, clear solutions, reduced tannins, but essentially no change in arabinose content.

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