Role of egg white protein gelling capacity on the processability and properties of compression-moulded films

This study aimed to assess the impact of the gelling capacity of powdered egg white protein (EWP) on the processability and properties of compressed-moulded films. Three commercial grades of EWP with varying gelling capacities and three protein-to-plasticiser ratios were selected for film preparation. The EWP structure was characterised by FTIR and XRD, and the relative abundance of proteins was estimated using LC-ESI-MS/MS. The rheological properties of the film-forming solutions (FFS), along with the mechanical, barrier, and optical properties of resulting films, were also evaluated. The EWP samples exhibited differences in secondary structure, soluble protein content, and protein profile, which were reflected in the viscosity, consistency, and elastic modulus of the FFS, all of which increased with gelling capacity. The processability and stability of the FFS were found to depend on the appropriate combination of gel strength and protein-to-plasticiser ratio. In addition to the protein-to-plasticiser ratio, the β-turn abundance in the secondary structure of the EWP film was the parameter most strongly correlated with Young's modulus (p < 0.01). However, the barrier properties of the films were significantly influenced solely by the protein-to-plasticiser ratio (p < 0.01), with higher plasticiser content resulting in increased oxygen and water vapour permeability.