Evaluation of methods for extraction and analysis of wood resin in birch kraft pulp

Pre-treatment procedures and extraction techniques for analysis of lipophilic extractives in chemical pulps were compared on unbleached and bleached birch kraft pulps. Long air-drying of pulp caused oxidation of polyunsaturated compounds, such as linoleic acid and betulaprenols. Five different extraction techniques were compared: Soxhlet, Soxtec, reflux, ultrasonic extraction and Accelerated Solvent Extraction. Only small differences in the extract yield and composition were found between the different extraction methods for unbleached kraft pulp. However, in the case of bleached pulp containing a high proportion of saturated fatty acids the reflux extraction technique with addition of KH2PO4 gave a 30% higher yield of saturated fatty acids than the other extraction techniques.