Preparation and characterization of gelatin/hydroxypropyl methylcellulose blended films incorporating zein/pectin composite particles

Gelatin (GA) and hydroxypropyl methylcellulose (HPMC) are inherently incompatible, hindering the formation of uniform composite films. In this study, the effect of GA/HPMC ratios on the microstructure and physicochemical properties of the blended films stabilized by zein/pectin composite particles (ZCPs) was investigated. The light transmittance of blended films was consistently lower than that of single-component films due to the partial miscibility between GA and HPMC. The blended films with low GA contents (<30 %) exhibited higher light transmittances, owing to the increased miscibility between GA and HPMC stabilized by ZCPs. As GA content increased, the blended films exhibited higher water vapor permeability and water contact angle, accompanied by reduced thermal stability and mechanical strength. The blended films containing ZCPs possessed emulsion-like microstructures similar to that of HPMC encapsulating GA droplets. Increased HPMC content amplified the stabilizing effect of ZCPs, resulting in smaller and more uniform droplet sizes that extended water diffusion pathways, thereby increasing water contact angle. This phenomenon also increased the thermal stability from 345.5 to 353 °C, tensile strength from 7.3 to 11.2 MPa and elongation at break from 7.1 to 8.5 %. These findings open up new avenues for the application of such emulsion-like films in food packaging. • The blended films with high HPMC content had good light transmittance. • The GA/HPMC blended films displayed a emulsion-like microstructure. • The blended films with a GA/HPMC ratio of 3:7 had the smallest droplet size. • The films with smaller droplet size had better mechanical properties.