Migration of chitosan films prepared by solvent evaporation and extrusion

Introduction: Chitosan has multiple applications and as inhibitor of microbial growth, there is interest in developing new methodologies to its incorporation into plastics, which would avoid microbial growth in foods. In the frame of the project “Preparation of active packaging with antioxidant and antimicrobial activity based on astaxanthin and chitosan” (PAPAAABAC), chitosan was extracted from shrimp by-products and used to prepare plastic films by solvent evaporation (casting) and extrusion. Material and Methods: Chitosan films were prepared by extrusion of polyamide and by casting. By casting, films were prepared at different concentrations (1%, 2%, and 3%) by dissolving chitosan in acetic acid aqueous solution 1% (w/v), with and without plasticizer (1% glycerol). By extrusion, chitosan pellets were made of polyamide 6 at 2%, 5%, 6%, 8%, and 10% with two different particle sizes (180 and 300 µm). Then, they were rolled in an extruder using a specific screw for polyamide. In order to determine chitosan in food simulants (ultrapure water and ethanol 95% (v/v)), it was degraded into the glucosamine units by hydrolysis and quantified by ultra high pressure liquid chromatography coupled with diode array detection after its derivatization with 9-fluorenylmethyl chloroformate. Results and conclusion: From the plastic films prepared by casting and by extrusion, only those prepared by casting without plasticizer presented chitosan migration that increases with the amount of chitosan added. These films could not be used to pack aqueous foodstuffs. However, the addition of a plasticizer (glycerol) has avoided the migration of chitosan. Therefore, the use of casting films with chitosan shall include a plasticizer in the formulation. Films prepared by extrusion presented no migration into both simulants indicating suitability to pack both aqueous and fatty foodstuffs.