Novel Bioactive Kefiran-Based Films Enriched with Grape Pomace Extract

The increasing demand for eco-friendly and functional packaging materials has driven research on biodegradable materials incorporating bioactive compounds. In this study, kefiran-based films (K; 3%) were developed and incorporated with grape pomace extract (GPE) at different concentrations (3K-0.5GPE, 3K-1.0GPE, and 3K-1.5GPE). The films were characterized based on their physicochemical, mechanical, antioxidant, and antimicrobial properties. It was found that the incorporation of GPE into the films increased the L*, a*, b*, and ΔE values, as well as the thickness, and improved UV radiation protection. FT-IR analysis revealed interactions between kefiran and the phenolic compounds of GPE, without altering the polymer structure. In addition, an increase in tensile strength and elongation at break was observed, evidencing a plasticizing effect of GPE, which also increased the water vapor permeability of 3K-1.5GPE. Solubility was not affected by the incorporation of GPE into the films. Regarding bioactive properties, the addition of GPE increased antioxidant activity and total phenolics. Antimicrobial assays showed activity only for the 3K-0.5GPE film against Listeria monocytogenes, with no activity against Escherichia coli. Overall, kefiran-based films containing GPE exhibit characteristics that position them as potential alternatives for sustainable, bioactive food packaging materials, thereby promoting the valorization of by-products from the wine industry.