Thermally-induced crosslinking altering the properties of chitosan films: Structure, physicochemical characteristics and antioxidant activity

Herein, thermal-induced modification of the properties of neat chitosan film was studied during the heating process at 90–130 °C for 24 h. By tracing the consumption of -NH3+, we found Maillard reaction occurred in heated films, which increased the degree of crosslinking. Heat treated films showed a more compact structure, leading to an increase in their tensile strength with the highest level of 54.3 MPa in the 110 °C treatment. Meanwhile, water solubility, swelling degree, water vapor and oxygen permeability of chitosan films decreased after thermal treatment due to the reduction of amino groups and their denser structure. In addition, the heated films had higher antioxidant capacity, while an optimum process displayed at 110 °C showed a 90% increase in DPPH• free radical scavenging when compared with the control. Summarily, the thermal treatment, especially 100–110 °C was a conditionally useful guide to improve the overall performance of chitosan film under the condition of 24 h-reaction time.