Comparison of the properties of composite films constructed from chitosan and gelatin from two jellyfish species

Composite films incorporating jellyfish (Rhopilema esculentum Kishinouye, RG; Stomolophus meleagris, SG) gelatin and chitosan (CS) at mass ratios of 7:3, 6:4, 5:5, 4:6 and 3:7 were studied. The 5:5 ratio exhibited superior mechanical performance, with tensile strength (TS) of 5.8 MPa (SG/CS) and 7.2 MPa (RG/CS), exceeding pure CS and fish gelatin (FG)/CS films by 1.1-6 times. The blueshifts of amide A bands in comparison to CS films confirmed increased hydrogen bonding in jellyfish gelatin/CS systems. SG/CS and RG/CS films revealed 54.5-67.7 % lower UV-visible light transmittance and 3 to 8 times higher opacity than FG/CS and CS films. Both SG/CS and RG/CS films had dense, continuous structures without phase separation, indicating good compatibility between jellyfish gelatin and CS. Compared with CS films, SG/CS and RG/CS films presented a 31.1%-51% lower water content (WC) and 46.6%-60.4% lower water vapor permeability (WVP), with water contact angle (WCA) increasing by 11.4 %-20.8 %, representing increased moisture resistance of the films. Additionally, thermal stability of SG/CS and RG/CS films was improved. This study provided valuable insights into the functional properties of SG/CS and RG/CS composite films, supporting their potential applications as biopolymer films in food packaging applications.