Chitosan films plasticized with choline-based deep eutectic solvents: UV shielding, antioxidant, and antibacterial properties

Deep eutectic solvents (DES) as plasticizers of chitosan film show great potential for food packaging. This paper introduced some novel antioxidant and antibacterial films based on chitosan and DES consisting of choline chloride (ChCl) and organic acids. The effects of the composition and contents of choline-based DES on structures, mechanical properties, thermal stability, contact angle, optical, antioxidant and antibacterial properties of chitosan films were studied. FTIR analysis showed that choline-based DES did exist in the chitosan film with good polymer matrix compatibility. Most of the films exhibited uniform, flat surfaces and cross sections. The Young's modulus of the films decreased inversely to the level of choline-based DES, and maximal mechanical characteristics were achieved for films plasticized with ChCl and acetylsalicylic acid. The addition of choline-based DES apparently reduced water contact angles, decreased the decomposition temperature and the thermal stability of chitosan films. In terms of antioxidant capacities and ultraviolet (UV) shielding, chitosan films plasticized with choline-based DES containing acetylsalicylic acid and vitamin C had strong UV shielding and antioxidant properties. Chitosan films plasticized with choline-based DES containing acetylsalicylic acid, malonic acid and lactic acid showed excellent antibacterial properties against Escherichia coli and Staphylococcus aureus. In conclusion, the chitosan film with the choline-based DES, especially for ChCl and acetylsalicylic acid showed a good application prospect in food active packaging.