Importance of eggshell cuticle composition and maturity for avoiding trans-shell Salmonella contamination in chicken eggs

• The relevance of cuticle properties on Salmonella penetration in eggs was assessed.
• Microbial growth on the eggshell surface and incidence of Salmonella penetrated eggs increases with hen age.
• Cuticle maturity and chemical composition determines the risk of egg contamination.
• A mature cuticle rich in proteins has the highest resistance against bacteria penetration.
• Cuticle compositional parameters can be used in selection programs to improve egg quality and safety.

The cuticle coating the eggshell surface is the first line of defense of the egg against bacterial ingress. However, the cuticle properties (i.e., thickness, degree of coverage, chemical composition) have a very large natural variability and this work analyzed how this variability influence the risk of eggs being contaminated by Salmonella. Microbial growth on the eggshell surface as well as the incidence of Salmonella penetration in eggs increases significantly with hen age for the groups (25, 35, and 52 weeks) considered in this study. It shows also that the cuticle is most effective against bacterial penetration between 6 and 72 h after eggs have being laid when this coating is fully mature and has not dried excessively. In contrast, freshly laid eggs can be easily contaminated as they have an immature cuticle which is not able to resist bacterial penetration. This study show also that the chemical composition of the mature cuticle determines the risk of trans-shell contamination by Salmonella. In particular, it shows that eggs with a cuticle rich in proteins have a decreased shell permeability and greater resistance against Salmonella penetration. The novel analytical technique used here to quantify the cuticle quality (based on infrared spectroscopy; ATR-FTIR) could be used in assisted selection programs aimed to improve the quality and safety of eggs.