Physicochemical and storage properties of chitosan-based films plasticized with deep eutectic solvent

This paper concerns novel, biodegradable and nontoxic materials for food-packaging. In order to obtain these properties, chitosan (Ch) and choline chloride (ChCl)-based deep eutectic solvent (DES) with malonic acid (MA), were used. The use of ChCl-MA mixtures as a potential plasticizer of chitosan (DD = 72 and 83%) films was proposed. All films with DES content ranging from 0 to 80 wt% were successfully prepared by a solution casting method. The properties of the DES-modified films were compared to those of the unmodified chitosan films. The effect of DES content on the structural (FTIR, SEM and AFM methods), mechanical, thermal and barrier properties of chitosan films was studied. The addition of ChCl:MA resulted in a significant increase in the elasticity. Chitosan films containing 80 wt% of DES exhibits Young's modulus lower by ca. 2400 MPa in comparison to the native chitosan films. According to the AFM images, chitosan-DES films possess higher roughness compared to the unmodified ones. Thermal properties were also influenced by the presence and content of DES due to the lower thermal stability of ChCl:MA mixture. Evaluation of water vapor permeability confirmed an increase in this parameter for all DES-modified films. Observed changes in chitosan properties increase the potential of this material being successfully used in food packaging.