Innovative smart packaging for fresh food monitoring using green silver and titanium dioxide nanoparticles

The rapid perishability of fresh food and growing environmental concerns about traditional plastic packaging require innovative, sustainable solutions for food preservation and real-time monitoring. However, current active and intelligent packaging technologies are often based on synthetic chemicals or non-biodegradable materials, limiting their safety and sustainability. This study addresses this gap by developing a multifunctional packaging film containing nanoparticles (NPs) of silver (Ag) and titanium dioxide (TiO₂) in a biodegradable polymer. The film comprises a composite material of chitosan (CH), potato starch (PS), and anthocyanins (An) extracted from red cabbage, with the anthocyanins encapsulated in starch nanocrystals. The resulting composite films exhibited significant pH-dependent properties, enabling them to serve as visual indicators of food freshness, with thicknesses of 0.15 ± 0.015 mm and 0.15 ± 0.022 mm, water contents of 19.14 ± 0.5 % and 10.27 ± 0.6 %, and water vapour permeability (×10⁻¹² g·m⁻¹·s⁻¹·Pa⁻¹) of 3.42 ± 1.9 and 1.64 ± 0.82 for the two synthesised films, respectively. The original grey-green Ag-NPs-based film changed color to yellow after milk spoilage, providing an intuitive visual cue for consumers or suppliers to detect milk spoilage. Similarly, the color of the TiO₂ NPs-based film changed from grey-green to brownish-grey in response to shrimp spoilage, indicating the decline in shrimp freshness. These color changes are attributed to the interaction of the nanoparticles with the pH of the food, with the anthocyanins in the film acting as the primary pH-sensitive indicator.