The effect of kraft delignification of wood on hemicelluloses and lignin DMSO - Accessibility

The dynamics of hemicelluloses (HC) and lignin (L) accessibility to dimethyl sulfoxide (DMSO) after extended and conventional kraft pulping of pine chips has been studied applying direct SEC analysis of DMSO extracts. It was found that HC and L accessibility to DMSO could serve as an indication of the degree of wood cell wall destruction. The DMSO-solubility of wood residues characterises the dynamics of HC and L dissolution during cooking. It was estimated that ca. 35 % of HC and ca. 20 % of L in unbleached pulps (yield 32-50 %) were soluble in DMSO. Correlations between wood residues constituents accessibility to DMSO and pulp yield as well as wood residue composition were evaluated. The molecular mass of accessible HC ranged from 33 kDa to 12kDa for M-w and from 20 to 6kDa for M-n depending on the cooking time and conditions.