Tuning structure and properties of gelatin edible films through pullulan dialdehyde crosslinking

Tuning structure of gelatin edible films by crosslinking with oxidized polysaccharides is a highly interesting approach, as thereby the random coil structure of gelatin changes towards a covalent network and thus the properties can be tailored. With this aim, a series of pullulan dialdehyde (PDA) with different molecular weights and aldehyde contents were successfully synthesized by periodate oxidation of pullulan, and subsequently being used for crosslinking gelatin edible films. The inclusion of PDA in gelatin films induced chemical crosslinking between the protein chains and consequently improved their water vapor barrier property and thermal properties. The water solubility of gelatin films decreased from 42.3 ± 2.1% to 18.7 ± 0.5% after PDA crosslinking, while the tensile strength of the crosslinked gelatin films was about 2.7 times that of neat gelatin film. Furthermore, PDA crosslinking provoked a significant browning coloration of the gelatin films, accompanied by a significant improvement in UV light barrier property. The results also indicated that the molecular weight of PDA might play an important role in affecting the network structure and properties of gelatin films. Collectively, PDA crosslinking can be considered to be a potential alternative for tuning structure and properties of gelatin edible films.