Improved properties of gelatin films involving transglutaminase cross-linking and ethanol dehydration: The self-assembly role of chitosan and montmorillonite

In this study, the chitosan and montmorillonite (MMT) were synergistically introduced to improve the properties of the gelatin films through self-assembly. The preparation of gelatin films (G), gelatin + MMT composite films (G + MMT), gelatin-chitosan bilayer films (G-CS), and gelatin + MMT-chitosan composite bilayer films (G + MMT-CS) involved transglutaminase (TG) cross-linking followed by ethanol precipitation and self-assembly process. The water contact angle of the composite bilayer films (G-CS and G + MMT-CS) was higher than 110° due to the formation of surface hydrophobic layer formed by self-assembly via hydrogen bonding and electrostatic interaction between gelatin and chitosan, but the MMT alone cannot improve the hydrophobicity of gelatin films. The water solubility (WS) of G + MMT, G-CS and G + MMT-CS films was significantly lower than that of G films. The mechanical and barrier properties were significantly improved due to the introduction of MMT and the surface deposition of chitosan, attributing to the increase of triple helix content and formation of bilayer structure, respectively. Moreover, MMT caused the decrease of sterilization thermal shrinkage from 49.54% to 34.00%. Interestingly, MMT facilitated the surface deposition of chitosan during self-assembly process. The mold growth of bread wrapped with G + MMT-CS was effectively inhibited during storage, implying potential application as antimicrobial food packaging materials.