Active chitosan-alginate films incorporating methyl eugenol for improved food packaging functionality and postharvest preservation performance

Abstract

The development of biodegradable active packaging materials is essential for improving food preservation while reducing reliance on petroleum-based plastics. In this study, chitosan–alginate composite films were prepared and functionalized with eugenol and its methylated derivative, methyl eugenol, and systematically evaluated in terms of structural, physicochemical, antimicrobial, antioxidant, biodegradation, and postharvest preservation performance. Structural analyses revealed strong intermolecular interactions and a reduction in film crystallinity upon bioactive incorporation, with a more pronounced amorphization effect observed for methyl eugenol. Compared with the control film, the methyl eugenol-loaded film exhibited significantly higher tensile strength (6.99 ± 0.21 MPa vs. 4.57 ± 0.17 MPa, p < 0.05) while maintaining moderate elongation at break (34.87 ± 1.13%). Water vapor permeability was significantly reduced by 28.4% (p < 0.05), indicating improved moisture barrier properties. Antioxidant assays demonstrated enhanced radical scavenging activity, while antimicrobial evaluation against Escherichia coli and Staphylococcus aureus showed significant bacterial inhibition (p < 0.05), with methyl eugenol exhibiting the strongest effect. Soil burial tests confirmed that all films remained biodegradable, with more than 65% weight loss observed after 28 days. Postharvest application was evaluated using cherry tomatoes (n = 30 per treatment) stored under ambient conditions (25 ± 2 °C) for up to 12 days. The methyl eugenol-functionalized films significantly reduced decay incidence and weight loss and better preserved soluble solids, titratable acidity, and antioxidant capacity compared with the control and eugenol-containing films (p < 0.05). These findings demonstrate that methyl eugenol enhances both film functionality and postharvest preservation performance, highlighting its potential for sustainable active food packaging applications.