CHANGE OF HYDROPHILIC PROPERTIES OF HEMICELLULOSES DURING COOKING

The paper deals with the transformation of hemicellulose from γ-cellulose to β-cellulose during cooking, contrary to the ordinary conception.β-Cellulose is little present in softwood but much in hardwood. Hardwood pulp, especially hardwood sulphate pulp, contains larger amouns of β-cellulose than γ-cellulose. It is due largely to the facts (1) the small amount of glucomannan which has larger affinity to water and, (2) rather lower degree of hydrophilic properties of xylan complex, It is generally accepted that α-cellulose is decomposed to β-cellulose, and furthermore, to γ-cellulose during cooking of softwood. Nevertheless, in view of hemicellulose, by cooking, especially by sulphate cooking, some of γ-cellulose in the wood is changed to β-cellulose, because of the decreased amount of hydrophilic residues of hemicellulose molecules, in spite of the decreasing in degree of polymerization of these molecules.