Alginate-based films incorporating bacteriophage vB_EcoM-P34 for in situ biocontrol of Escherichia coli O157 on Kashar cheese.

The development of innovative antimicrobial packaging systems is critical for ensuring food safety. Bacteriophages are promising biological agents for the prevention and control of the growth of foodborne pathogens. This study developed a sodium alginate-based antibacterial film incorporating bacteriophage vB_EcoM-P34 for the control of Escherichia coli O157:H7 on the surface of cheese. Films were evaluated in terms of physicochemical properties, surface morphology, mechanical properties, and antibacterial activity. Phage incorporation resulted in a limited reduction in titer from 10.31 to 9.00 log PFU/cm2 after film formation (p < 0.05), indicating high retention of phage viability within the matrix. The films exhibited a rapid release profile, with 96.44% of the embedded phages (8.68 log PFU/cm2) released within 15 min and reaching 97.78% at 240 min, demonstrating near-instantaneous availability. Phage incorporation did not significantly (p > 0.05) affect film thickness (0.073-0.074 mm), moisture content (~39%), or mechanical properties, confirming structural integrity of the alginate matrix. In vitro assays showed a 3.12 log CFU/cm2 reduction of E. coli O157:H7 after 24 h at 25 °C, while control films exhibited only a 0.55 log reduction. In Kashar cheese stored at 4 °C, phage-loaded films achieved a 1.67 log CFU/cm2 reduction within 24 h and a total reduction of 2.95 log CFU/cm2 after 7 days, whereas phage-free films showed no significant antibacterial effect. Phage titers on cheese remained stable (6.67 to 6.37 log PFU/cm2), supporting sustained activity despite matrix-related diffusion limitations. These results demonstrate that sodium alginate films enable high phage stability, rapid release, and effective biocontrol in situ.