Shikonin-loaded bioactive gelatin films with antibacterial activity against Listeria species and antioxidant properties to extend the shelf-life of raw refrigerated beef.

Certain Listeria species, particularly L. monocytogenes, can colonize refrigerated meat surfaces and form biofilms, both threatening product safety and shortening shelf-life. This study developed a shikonin-loaded gelatin-based film (GEL-SKN film). Fourier transform infrared spectroscopy confirmed non-covalent interactions between SKN and gelatin, while scanning electron microscopy revealed uniform dispersion of SKN in the gelatin matrix. These interactions improved SKN dispersion and increased the tensile strength of film to 34.26 MPa. GEL-SKN films exhibited strong antibacterial activity against Listeria monocytogenes, Listeria ivanovii, and Listeria seeligeri at 4 °C and 25 °C. At both temperature, the Listeria count treated with GEL-SKN film (1.88-2.97 log10 CFU/mL) was significantly lower than that in GEL film (3.23-3.84 log10 CFU/mL). Transmission electron microscopy and biochemical leakage assays demonstrated that SKN disrupted the Listeria cell membranes integrity, leading to the leakage of nucleic acids and proteins. The films also showed potent antioxidant activity, with DPPH and ABTS radical scavenging rates of 73.34 %-74.33 % and 88.03 %-88.18 %, respectively. In simulated preservation tests on refrigerated beef (stored at 4 °C for 7 days), GEL-SKN films maintained the pH of beef within the fresh range (5.84-6.01), inhibited lipid oxidation (0.69-0.76 mg MDA/kg), reduced the accumulation of total volatile basic nitrogen (12.25-15.40 mg/100 g), and decreased Listeria counts by 1.04-1.11 log10 CFU/g. Consequently, the sensory acceptability period of refrigerated beef was extended from 3 days to 7 days. These results demonstrate that GEL-SKN films integrate antibacterial and antioxidant functionalities, thereby providing an effective and sustainable strategy to improve microbial safety and oxidative stability of refrigerated meat products.