Development of alginate-based film incorporated with anthocyanins of red cabbage and zinc oxide nanoparticles as freshness indicator for prawns

The objective of this study was to develop pH-sensitive film indicators for intelligent food packaging by incorporating red cabbage anthocyanins (RCA) and zinc oxide nanoparticles (ZnO NPs) into an alginate (Alg) film, aiming to mitigate the risk of foodborne illnesses. The films were fabricated using a solvent-casting method and crosslinked with a calcium chloride (CaCl2) solution. Thorough evaluations of the films' physical, mechanical, and structural properties demonstrated significant improvements in elastic modulus and UV/vis light barrier characteristics, reduced water vapor permeability (WVP), and moisture content attributed to integrating RCA and ZnO NPs. The resulting film displayed discernible color changes when exposed to various pH buffer solutions and ammonia vapor, indicating heightened sensitivity to pH fluctuations due to the presence of ZnO NPs. Visual assessment using prawns as test specimens revealed a color shift from violet (indicating satisfactory condition) to blue-greenish (indicating spoilage), corroborated by colorimetric analysis. Moreover, the Alg/ZnO/RCA film exhibited antioxidant and antibacterial properties, demonstrated biodegradation activity, and showed no toxic effects on RSC96 cells, further underscoring its potential as an effective freshness indicator for food products.