Bacteriophage emulsion for prevention of Salmonella contamination in eggshells

Salmonella contamination of eggs poses a significant public health risk, contributing to foodborne illnesses worldwide and necessitating effective control measures to ensure food safety. Although chemical sanitization followed by refrigeration has been widely recommended to control bacterial contamination, it has limitations, including concerns over chemical residues, microbial resistance, and practical constraints in regions with limited cold-chain infrastructure. Bacteriophages are a promising alternative because of their specificity and ability to infect and lyse bacterial hosts. However, the application of phages to eggshells is hindered by rapid desiccation, which reduces their efficacy over time. In this study, we developed a bacteriophage-mineral oil emulsion to improve phage stability and enhance the antimicrobial efficacy on eggshell surfaces. A lytic Salmonella phage, pSe_SNUABM_01, was isolated, characterized, and incorporated into a mineral oil-based emulsion. The formulation was optimized by adjusting the oil-to-water ratio, mixing speed and emulsification duration. The 4:6 (v/v) oil-to-water ratio at 3000 rpm for 7 min demonstrated the highest stability after 21 days. On eggshell surfaces, the phage-emulsion coating significantly reduced Salmonella loads compared to untreated and conventionally coated eggs and maintained antibacterial activity over time. The emulsion also covered eggshell pores and cracks, thereby mitigating bacterial penetration. These findings suggest that phage emulsion coating could serve as a practical and effective strategy for reducing Salmonella contamination in eggshells, particularly in settings where refrigeration is not feasible. This approach combines physical protection with targeted antimicrobial activity, providing a viable alternative to conventional methods.