Colorimetric Films Based on Mortiño, Sugarcane Bagasse Cellulose, and Silver Nano-particles for Food Packaging

The development of multifunctional packaging materials that preserve food quality and provide visual information on freshness has attracted increasing attention as an alternative to conventional petroleum-based packaging. In this work, PVA-based composite films were fabricated using poly(vinyl alcohol) (PVA), cellulose extracted from sugarcane bagasse (Saccharum officinarum), silver nanoparticles (AgNPs), and Vaccinium floribundum (mortiño) extract as a pH-responsive colorimetric component. The mortiño extract showed a visible pH-dependent transition from red under acidic conditions to yellowish tones under alkaline conditions across the tested pH 2–12 range. UV–Vis spectroscopy displayed an absorption band at approximately 410 nm consistent with the localized surface plasmon resonance of AgNPs, while FTIR and Raman spectra were consistent with incorporation of cellulose and mortiño-derived constituents into the PVA matrix. SEM/EDX revealed cellulose-rich structures and silver-containing domains in the analyzed regions, and DTG profiles showed formulation-dependent changes in thermal degradation behavior. In agar-diffusion assays, the formulation containing PVA, cellulose, AgNPs, and separately added mortiño extract produced reported inhibition-zone diameters of 15 mm against Staphylococcus aureus and 10 mm against Escherichia coli. During four days of ambient storage, the films showed food and time dependent visual changes with cheese, beef, and shrimp. These findings support further investigation of PVA-based composite films incorporating renewable and agroindustrial-derived components as candidate freshness indicators.