Physical and structural properties of whey protein concentrate - Corn oil - TiO₂ nanocomposite films for edible food-packaging

Interest in polymer technology based on biodegradable and edible films has increased dramatically, in hopes of creating a circular economy with little to no environmental impact. In this study nanocomposite films with a glycerol/WPC ratio of 4/5 were prepared from emulsions containing 2.5, 5.0, or 7.5 wt.% WPC and 2 wt.% corn oil. Films also contained a load of 0.5 wt.% TiO₂. Emulsions were prepared with two different droplet sizes: conventional (from 300 to 700 nm) and nano (from 60 to 80 nm). Films were analyzed for color, water vapor permeability, thermogravimetric, mechanical/tensile properties, infrared behavior, and structure. Advanced X-ray microscopy based on small and wide-angle scattering contrast was used to investigate the nanocomponents in the films, allowing the identification of the main scattering species. Film that was prepared from starting systems with nano droplets (60 nm), the highest protein concentration (7.5 wt.% WPC), and TiO₂ loading had the greatest E’ (elastic modulus, 19.2 MPa), E (Young modulus, 19.4 MPa), and ε_b (elongation at break, 119 %) values. This nano-based film had suitable physical properties for cheese packaging and other similar applications. In all films, data showed a close correlation between film structure and mechanical/tensile properties.