Inactivation of Salmonella Enteritidis on eggshells by lactic acid spray

Egg safety and quality is a long-standing concern for producers and consumers. Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) is the prevalent egg-product-related foodborne pathogen. The treatment with organic acids, including lactic acid, for the elimination and control of foodborne pathogens is generally recognized as safe, and is widely applied in many foods. In this study, we found that spraying with 2% lactic acid on the eggshell surface effectively reduced Salmonella Enteritidis counts. Agar-filled eggs were used to study the bacterial penetration of the eggshell (eggshell and membranes), and the contamination of the whole egg contents was investigated. No significant differences were observed between the Salmonella Enteritidis penetration in lactic acid sprayed and unsprayed eggs stored at 4 °C. The Haugh unit, albumin pH, and eggshell strength values were similar in the sprayed and washed eggs. Average Haugh unit scores for sprayed eggs were still Grade A within 3 weeks. However, the lactic acid treatment decreased the eggshell strength and cuticle layer thickness. SEM observations confirmed that spraying of lactic acid damaged the cuticle integrity. The results from our research will indicate that lactic acid spray is highly effective in reducing Salmonella contamination on the eggshell surface, but trans-shell penetration was demonstrated in the eggs stored at room temperature. Consequently, low-temperature storage is important for the prevention of recontamination of the egg after spraying.