STUDIES ON RAISING EXTRACTION OF TANNIN EXTRACT FROM LARCH BARK
Zheng Zhifang Zhang Lijun Tong Xiantao Wang Shengguo Yang Xuesong(Northeast Forestry University)
Extraction methods of Larch bark for better tannin recovery are studied. A lot of Tannin has been achieved by extracting with certain additives. The experimental results Showed that extraction with chemical additives, such as sodium hydroxde, ethanol, removed a great amount of extractives from larch bark than did with water. The quantity and quality of tannin extract also greatly improved. The optimal conditions of the extraction were determined by crossed test. The most suitable conditions for recovery tannin extract from larch bark are 1.25 percent of sodium hydroxide based on dry weight of bark and 35 percent ethanol—water solution, temperature 90℃, 5 hours. The extraction rate of extractives and tannin have increased by 11.4 percent and 12.7 percent respectively as compared with water. The purity of tannin extract has increased by 11.48 percent.