Bio-based gelatin–TiO₂–purple basil extract nanocomposite films for monitoring fish freshness

A pH-responsive and user-friendly food packaging indicator that detects ammonia was successfully developed by incorporating gelatin matrices, purple basil anthocyanins, and nano-TiO₂ (1–2% by weight) into its composition. SEM images indicated TiO₂, and anthocyanin were dispersed throughout the film matrix. Physical properties, mechanical properties, antimicrobial and antioxidant properties, structural and appearance properties of the films were investigated. TiO₂ and purple basil extract increased the thickness, improved the mechanical and physical properties of films. Also, nanocomposite films containing TiO₂, and purple basil extract showed acceptable antioxidant properties and antimicrobial effects, especially against gram-positive bacteria Staphylococcus aureus. The effectiveness of the biodegradable films in assessing the quality of fish was examined by subjecting them to storage at 4 °C for 15 days. It was observed that the packaging indicator underwent a discernible color change, transitioning from purple to green. This change occurred alongside an increase in total volatile basic nitrogen levels and a shift in pH within the packaged sample. This study suggested TiO₂ can delay the occurrence of food spoilage by directly imparting the active film with good antibacterial activity; the crosslinking of TiO₂ and the film matrix could improve the barrier properties of actives films. These biodegradable active films may be suitable replacements for plastic packaging materials, detect food deterioration and prolong shelf life, thereby reducing waste.