4. Conclusion
Antioxidant active films, based on an ethylene–vinyl alcohol copolymer and natural antioxidants, were successfully developed by casting. Thermal analysis revealed that the materials had a deterioration of the crystallinity structure and approximately 4% of residual solvent, which resulted in a reduction in barrier properties compared to materials obtained by extrusion. The incorporation of antioxidants did not greatly affect the polymer properties and, in the case of materials containing green tea extract and quercetin, permeability values even decreased.
Release of active agents depended on the affinity of the antioxidants for the food simulants, the release of ascorbic and ferulic acid being higher in aqueous simulants, and the release of quercetin and green tea extract higher in ethanolic simulant. The antioxidant activities of the films were tested against lipid oxidation of brined sardines. The films with green tea extract were the most effective, slowing down the peroxide values from 27 to 12 meq/kg fat on the fifth day of storage, and also reducing the malondialdehyde concentration by 25% during the storage time.