Wool keratin film plasticized by citric acid for food packaging

Wool keratin (natural resource) and citric acid (effective preservative) were mixed in water to produce a transparent film for application in active packaging. This film showed excellent biocidal effect, high elongation value (600%) and little loss of keratin after immersion in water. The capability of citric acid to bind keratin macromolecules by hydrogen bonds is probably responsible for the improvement of film's extensibility. On the other hand, the study of FT-IR spectrum allows understanding that the presence of citric acid in aqueous solution enhances the content of alpha helix structure in the film, with a reduction in the amount of side chain and disordered conformations in the macromolecular structure. Carrot shelf-life was qualitatively improved with this film in comparison with a commercial film for preserving food. Consequently, this film can have possible application for food packaging as a substitute of synthetic polymers replacing them with a natural, environmental friendly and renewable resource.