Abstract: The safety of egg product which causes public concern is always the hotspot of research. As the popularization of welfare poultry rearing, the chance of eggs being contaminated by microorganisms increases. In addition to strengthen feeding management, it is also important to strengthen the egg's own protective barrier to resist bacterial invasion. The cuticle, an invisible layer on the surface of eggshell, is formed in the uterus at 1.5-2.0 h before oviposition. The cuticle is a natural defense preventing microorganism penetration across the eggshell. It was reported that eggs with thicker cuticle had a lower bacteria penetration rate compared with the eggs with thin cuticle layer. The eggs' cuticle is mainly composed of glycoprotein (90%), polysaccharides (4%), lipids (3%) and inorganic phosphorus in the form of hydroxyapatite crystals (3%). The eggshell cuticle contains several antimicrobial proteins, like lysozyme C, ovotransferrin, ovocalyxin-32, which can prevent bacterial trans-shell penetration effectively. Moreover, the cuticle also has many other functions:termination of calcite crystal growth during shell formation, as a lubricant to facilitate egg rotation in the uterus, extension the eggs' storage time by regulating the exchange of water and air. In this paper, the structure, biological function, evaluation method and factors affecting the quality of cuticle are reviewed, and the existed problems are discussed.

Key words: eggshell cuticle, egg safety, antimicrobial activity