Fabrication and characterization of polyvinyl alcohol/sodium alginate loaded carvacrol/silica hollow microspheres composite hydrogel as a colourimetric freshness indicator

A hybrid hydrogel consisting of anthocyanin (ATH), sodium alginate (SA), polyvinyl alcohol (PVA) and carvacrol (CA) loaded silica hollow microspheres (SC) was designed and fabricated as a colorimetric freshness indicator with antibacterial activity for monitoring meat spoilage. The microstructure and physicochemical properties of the hybrid hydrogels were investigated. The carvacrol could be loaded into silica microspheres, and the maximum degradation temperature raised to 179.6 °C due to the formation of hydrogen bonds between carvacrol and SiO2 microspheres. ATH and SC composite were well compatible with PVA/SA hydrogel with intramolecular hydrogen bond interactions. The three-dimensional network structure of the PVA/SA hydrogel was disrupted with increasing SC content, resulting in a gradual decrease in thermal stability, swelling capacity and tensile strength of the hydrogel. The SC-PVA/SA-ATH hydrogels exhibited satisfactory antibacterial ability against E. coli and S. aureus due to the effective release of CA from the hybrid hydrogel, and the inhibition ratio of SC3-PVA/SA-ATH was over 95%. The meat preservation experiment revealed that the hydrogel indicators exhibited distinctive color changes during the process of meat spoilage quality changes, indicating its promising application prospect in food preservation packaging.