Active Chitosan Films Enriched with Yerba Mate Kombucha Infusion: Formulation and Characterization.

The development of bio-based active packaging materials has gained increasing attention as a sustainable alternative to synthetic plastics. In this study, chitosan-based films incorporating yerba mate kombucha infusion (YMK-I) were developed and fully characterized. Films were prepared using different YMK-I concentrations (25-100% v/v) as solvent, with acetic acid-based chitosan films as controls. The infusion showed pH 2.5, titratable acidity of 3.5%, total solids of 6%, high phenolic content (1085 mg GAE/L), and reducing sugars (18.3 g/L). Acetic and lactic acids were identified by high-performance liquid chromatography (HPLC). Minimum Inhibitory Concentration (MIC) values ranged from 0.03 µg/mL for Staphylococcus aureus to 0.3 µg/mL for Escherichia coli and Pseudomonas aeruginosa. Rheological results indicated that YMK-I performed similarly to acetic acid as a solvent. Fourier Transformed Infrared with Attenuated Total Reflectance (FTIR-ATR) suggested interactions between chitosan and bioactive compounds. Thermal analyses showed that YMK-I acted as a plasticizer and introduced thermolabile components, altering glass transition and degradation behavior. Increasing YMK-I content reduced tensile strength and increased elongation, indicating greater flexibility, while water vapor permeability increased due to hydrophilic compounds. Films enriched with YMK-I exhibited high antioxidant activity (Radical Scavenging Activity > 85%) and strong antimicrobial effects (>98% inhibition) against E. coli and S. aureus. These results highlight the potential of chitosan-kombucha films as multifunctional materials for specialized applications.