Novel “all-in-one” multifunctional gelatin-based film for beef freshness maintaining and monitoring

In this study, a novel multifunctional food packaging was developed by incorporating alizarin (AL) and oregano essential oil Pickering emulsion (OEOP) into a gelatin film matrix. The incorporation of OEOP and alizarin improved the UV-vis resistance property of the film, blocking almost all UV-vis light (decreasing 71.80% to 0.06% at 400 nm). The elongation-at-break (EBA) was 4.02 times of that of gelatin film, indicating the improved mechanical properties of the films. This film showed a significant color change from yellow to purple in the pH range of 3-11 and a considerable sensitivity to ammonia vapor within 4 min, which was attributed to the deprotonation of the alizarin molecule. The film's antioxidant and dynamic antimicrobial capacity was significantly improved owing to the sustained release effect of OEOP. Furthermore, the multifunctional film effectively slowed down the beef spoilage rate and provided real-time visual monitoring of freshness through color changes. Additionally, the color change of the beef quality was linked to the RGB values of the film through a smartphone APP. Overall, this work broadens the possibilities of applications in the food packaging industry for multifunctional food packaging film with preservation and monitoring functions.