Change in the chicken eggshell cuticle with hen age and egg freshness

For a fuller understanding of the functionality of the eggshell cuticle, we conducted a detailed study using a wide array of analytical techniques (scanning and transmission microscopy), energy dispersive x-rays, and attenuated total reflection-Fourier transform infrared spectroscopy to analyze the structure, morphology, and chemical composition of this organic coating. This study shows that the cuticle has a compositional gradation with an outer part richer in proteins and an inner part richer in sulfated polysaccharides and phosphates. It also shown that the cuticle composition, thickness, and degree of coverage are highly dependent on hen age and egg freshness. During the course of the first laying year, the thickness and degree of glycosylation of the cuticle decreases with hen age, and at the end of the laying cycle, the cuticle is significantly depleted in lipids. There are also well-defined compositional changes in the cuticle of freshly laid eggs as time passes and there is a notable increase in the permeability of the eggshell after 24 h due to cuticle drying. We discuss how these changes in the cuticle can affect the food safety of eggs in relation to the risk of trans-shell contamination by bacteria (i.e., Salmonellosis).