Physicochemical properties of keratin extracted from wool by various methods

Keratin from wool fibers was extracted with different extraction methods, for example oxidation, reduction, sulfitolysis,and superheated water hydrolysis.Different samples of extracted keratin were characterized by molecular weight determination, FT-IR and NIR spectroscopy,amino acid analysis, and thermal behavior.While using oxidation, reduction, and sulfitolysis, only the cleavage of disulfide bonds takes place; keratin hydrolysis leadsto the breaking of peptide bonds with the formation of low molecular weight proteins and peptides. In the FT-IR spectraof keratoses, the formation of cysteic acid appears, as well as the formation of Bunte salts (-S-SO3-) after the cleavage ofdisulfide bonds by sulfitolysis. The amino acid composition confirms the transformation of amino acid cystine, which istotally converted into cysteic acid following oxidative extraction and almost completely destroyed during superheatedwater hydrolysis. Thermal behavior shows that keratoses, which are characterized by stronger ionic interaction andhigher molecular weight, are the most temperature stable keratin, while hydrolyzed wool shows a poor thermal stability.