Effect of precipitation methods on physicochemical properties of keratin films produced from chicken feather waste

Engineering keratin plastics from chicken feather wastes is highly attractive from an environmental prospect but challenging due to the influence of extraction routes on the macromolecular keratin features. In this study, the effect of precipitation methods on desired properties of biodegradable keratin films was investigated. Keratin was extracted from an industrial chicken feather waste by sulfitolysis, and further recovered using hydrochloric acid (KHA), citric acid (KCA), sodium chloride (KSC), and acetone (KAT) as precipitating agents. Keratin films containing glycerol at 25 wt% were produced by compression molding. All keratin films were nearly colorless and highly transparent to visible light while exhibiting good UV barrier properties. The KAT and KSC films showed greater ductility (epsilon(break) > 50%) compared with KHA and KCA, which was correlated with broader molecular weight distributions and less crosslinking in the former keratins. Importantly, disulfide bonds created in the processing led to keratin films with low water solubility. Larger surface hydrophobicity was attained from keratin recovered by organic solvent precipitation (KAT). These results advance the understanding of precipitating agents as physicochemical property modifiers of biodegradable keratin films for food packaging and other applications.