Effect of glyoxal concentration on the properties of corn starch/poly(vinyl alcohol)/carvacrol nanoemulsion active films

The corn starch (CS) / poly(vinyl alcohol) (PVA) / carvacrol nanoemulsion (CNE) active films were developed via a facile glyoxal cross-linking reaction. The molecular interactions within the film-forming solutions were measured by rheological property. The morphological, structure, and chemical characteristics of the active films were carried out using SEM, FTIR, and XRD. The film’s properties were measured in terms of swelling ratio, gas permeability, mechanical, optical, antioxidant and antimicrobial properties. When the concentration of glyoxal was higher than 3.0 %, the extent of cross-linking between polymeric components increased, which caused the macropolymeric network to become denser. The addition of glyoxal improved the compatibility of CS and PVA blends and induced an enhanced smoothness and rigid fracture in the structure of the films. The water-resistance and mechanical properties of the active films were enhanced with the increase of glyoxal concentration. However, the gas permeability and opacity decreased accordingly. Specially, after cross-linked, the volatilization rate of carvacrol decreased, which was beneficial to the films for enabling long-term antioxidant and antimicrobial activities. This work offers a novel method for preparing CS/PVA-based films with great ductility, strength, and water-resistance for many potential applications, such as packaging engineering and circular development areas.