ABSTRACT
Understanding the natural antibacterial defences of egg white and their regulation Nicolas Guyot, Sophie Réhault-Godbert, Yves Nys, INRA, France; and Florence Baron, INRA – Agrocampus Ouest, France
1 Introduction
2 Egg white antimicrobial molecules
3 Environmental and physicochemical conditions controlling bacterial growth and dispersion in egg white
4 Variability of egg white natural defences induced by hen-associated factors
5 Environmental variability of physicochemical and antibacterial properties of egg white during egg storage
6 Environmental variability of physicochemical and antibacterial properties of egg white during egg incubation
7 Conclusions
8 Where to look for further information
9 References
The avian egg white (albumen) is an aqueous solution of proteins. It is composed of 84-89% of water, the dry matter being constituted mostly of proteins (90%) and small amounts of carbohydrates, vitamins and minerals. The major function of these constituents is to provide nutrients and to protect the developing embryo and the highly nutritive egg yolk against invading bacteria. Egg white is a biological fluid secreted into the oviduct lumen by tubular glands and epithelial cells of the magnum, a specific segment of the oviduct. The egg white surrounds the egg yolk before being covered by eggshell membranes and the eggshell. Egg white is poor in nutrients available for the microorganisms (e.g. iron) and contains a great number of molecules that contribute to its remarkable antimicrobial properties. It is well established that avian egg white possesses antibacterial properties. The first demonstration of bactericidal effect was probably done by Wurtz (1890) on Bacillus anthracis and other bacteria; these findings were confirmed later by Laschtschenko (1909). A thermolabile enzyme was suspected to be involved in this activity. This bactericidal molecule was first identified by Fleming (1922) and named lysozyme. Thereafter, additional egg white proteins with antibacterial properties were reported.
