The Hydrothermal Degradation of Wool Keratin

Abstract

The most marked chemical reaction occurring during the treatment of wool keratin with water or steam at high temperatures is the conversion of cystyl residues to lan thionyl residues and also, apparently, to alanyl residues. The degradation of some lysyl and aspartyl residues also occurs during treatments at 150°, together with probable losses of prolyl, threonyl, seryl, isoleucyl, phenylalanyl, and asparaginyl or glutaminyl residues. The formation of some glycyl residues was also detected. It is postulated that, as a result of the treatments of wool with water, some peptide bonds are slowly hydrolyzed, enabling comparatively high molecular-weight peptides together with lower molecular-weight material to be dissolved from the wool. After treatments of long duration or at high temperatures, these peptides are progressively hydrolyzed to lower molecular-weight peptides, free amino acids and other degradation products. Heat setting of wool initially containing 25% moisture results in only slight changes in the chemical and physical properties at 120° during 30 min or shorter times.