Carvacrol-Containing Hemicellulose/Methylcellulose Plant-Based Coatings and Films: Evaluation of Antimicrobial Activity, Biodegradability, and Cytocompatibility

This study investigated the antimicrobial efficacy, biodegradability, and cytotoxicity of carvacrol-infused hemicellulose/methylcellulose (HB/MC)-based coating solutions and films for active food packaging applications. Micro-emulsified (M) and coarse (C) HB/MC solutions with 1 or 2% carvacrol (Car) were investigated. Their antimicrobial properties were evaluated by applying the solutions directly to eggshell surfaces (coating) or headspace (film). Against Salmonella enterica, the 2% carvacrol micro-emulsified coating (HB/MC+Car-2%/M) produced the greatest bacterial reduction, reaching 8.35 log10 units relative to the untreated control by Day 7. Under the same conditions, the corresponding coarse-emulsified coating (HB/MC+Car-2%/C) achieved a 2.10-log10 reduction. When evaluated as a headspace-active film, HB/MC+Car-2%/M achieved a 6.28-log10 reduction, demonstrating the superior antimicrobial performance of the direct-contact micro-emulsified coating. Biodegradability, assessed via biochemical oxygen demand (BOD), evidenced 100% biodegradation for all formulations under aerobic conditions. The highest BOD value was observed in HB/MC+Car-2%\M, indicating elevated microbial activity. Cytotoxicity evaluation using the MTT assay confirmed that all coating solutions were non-toxic, with HB/MC+Car-2%\M promoting the highest cell viability across tested concentrations. These results demonstrated that industrial crops and by-products could be used as carriers for bioactive agents via a micro-emulsification step, thereby significantly enhancing the functional performance of plant-based materials, offering a promising route for developing safe, biodegradable, and plant-based antimicrobial coatings and packaging materials.