Characterization and release of casein‑sodium alginate embedding phage edible film and the application in controlling of Salmonella contamination in food

Abstract

Salmonella remains a major foodborne pathogen responsible for food poisoning and poses a serious threat to public health. This study has developed an edible antimicrobial film using bacteriophage (phage) SaTp-04, specifically designed to capture and eliminate Salmonella in food. Optimal film conditions were achieved using casein (CA) and sodium alginate (SA) as the matrix, glycerol as the plasticizer, and phage protector. The mechanical properties and phage encapsulation rate were used as response variables. The presence of phage SaTp-04 did not significantly alter the thickness, tensile strength, elongation at break, water vapor permeability, moisture content, or water solubility of the film. Furthermore, the Fourier Transform Infrared spectroscopy, X-ray diffraction, and microscopic morphology of the phage film were similar to those of the phage-free film. The phage titer in the film remained stable for up to five weeks at 4 °C. Phage release from the film in water followed a first-order kinetics model (y = 85.312 × (1-e^−0.106x), R² = 0.9687). The release amount and rate were lower at 4 °C on LB plate surfaces than at 25 °C. The phage film inhibited Salmonella growth on fresh chicken breast and carrots at 4 and 10 °C. The surface of chicken breast packaged with the phage film showed a reduction of approximately 6 log CFU/cm² in Salmonella compared to the control, while the carrot surface demonstrated a reduction in Salmonella to below the detection limit (10 CFU/cm²) at 37 °C. These results confirm the feasibility of using phage SaTp-04 CA–SA edible films for food safety, providing a viable strategy for developing targeted capture packaging for foodborne pathogenic bacteria.