Formation mechanism of egg white protein/κ-Carrageenan composite film and its application to oil packaging

Natural biopolymers have the potential to be used as modern green food packaging materials because of their excellent biocompatibility and biodegradability. In this manuscript, egg white protein (EWP) and κ-Carrageenan (κ-C) were mixed to prepare a composite film. The effects of EWP contents on the mechanical, physical, barrier and microstructural properties of the composite film were investigated. Scanning electron microscopy (SEM) images showed that the disorder degree of the composite film was enhanced as the mass ratio of EWP increased. In addition, the elongation at break (EAB) and light transmission of the composite film were improved to 10.85% and 53.3%, respectively. However, the oxygen permeability, water vapor permeability (WVP) and water soluble time were notably reduced to 4.17 meq/kg, 1.59 g mm/m2·s·Pa and 29.9 s, respectively. Fourier transform infrared spectroscopy (FT-IR) and chemical interaction analyses indicated that the increase of mass ratio of EWP reduced the hydrogen bond interactions of the composite film, resulting in a decline in the tensile strength (TS), while increase of the degree of nonspecific crosslinking and the electrostatic interactions. The composite film was used as food packaging material in edible oil packaging. It was found that the composite film could effectively delay the rancidity of oil during storage compared to unpackaged and brand film. Moreover, the TS and water soluble time of the film improved to 23.31 MPa and 64 s, respectively, while the EAB reduced to 16.64%. Our study enriched the preparation of the edible film, the EWP and κ-C composite films would have extensive applications in the food packaging industry.