The primary function of the avian egg is to support the development of an embryo outside the hen’s body by providing nutrients and efficient protection against physical, microbial and thermal challenges. The avian egg constitutes a unique model of passive innate defences (eggshell, antimicrobials, etc.) as only a few bacteria including Salmonella Enteritidis are able to survive in the egg. Any alteration of these defences is associated with economic losses (cracked eggs) and risks for consumers (salmonellosis). Egg protection against bacteria relies on physical defences, the eggshell and the vitelline membrane (VM) that surrounds the yolk and, on the physicochemical properties (alkaline pH, viscosity) and antimicrobial proteins of the egg white (EW). These structures all contribute to protect the yolk (maintained in the centre of the egg by two chalazae) that is highly susceptible to bacterial contamination. Thanks to the hen genome sequencing, a myriad of antibacterial proteins (>100) have recently been discovered in the egg and besides the well-known antibacterials, lysozyme and ovotransferrin, our laboratory characterized some novel candidates extracted from the EW and VM (Ovalbumin-related protein X, AvBD11, gallin…). The role of these minor compounds in the egg antibacterial defence, their regulation by hen’s physiology and their stability during egg storage remains unknown. Indeed, the activity of these molecules is likely to be modulated by changes in the specific physicochemical properties of EW that occur during egg storage or depending on hen’s age. In parallel, genetic selection for sustainable egg production tends to lengthen the laying period (from 70 wks up to 100 wks) while improving egg production persistency. However, this approach remains currently limited by the negative effects of hen age on eggshell quality, on EW viscosity and on VM strength. These changes induced by hen’s age and by egg storage conditions are expected to have a substantial impact on egg protective systems that guarantee the hygienic quality of eggs and, which minimize cross contamination that may occur during separation of egg contents (egg products). This question needs to be urgently addressed with regard to egg and egg product safety and technological issues. The main objective of the EQLIPSE program is therefore to characterize the effect of the hen age on both natural defences and quality of eggs, and their subsequent alterations during egg storage. This project is divided into four work packages (WP1, WP2, WP3, WP0) combining complementary approaches (biochemistry, molecular biology, microbiology, biophysics, biological imaging) including some innovative methods (Raman microspectroscopy, tomographic imaging) to investigate internal egg quality and its alteration by hen age and egg storage. In WP1, we will investigate the combined effects of hen age and egg storage conditions (time, temperature) on the quality and antimicrobial properties of eggs. This part will explore for the first time the interaction between these two factors and the impact of the laying cycle extension on egg quality. In WP2, our objective will be to assess the relevance of a controlled storage atmosphere to correct internal egg quality defects induced by advanced hen age or egg storage. WP3 aims to decipher the molecular mechanisms underlying the variability of internal egg defences. In this WP, we will pay a particular attention to the EW and VM antibacterial proteins that are affected by hen age or egg storage, and to the physicochemical parameters influencing VM structural integrity and egg antibacterial activities. All combined information generated in this project will be integrated in WP0 and used to propose recommendations and new innovative tools to professionals, in order to improve the internal quality of table eggs for a prolonged period, and to implement the ability of eggs to processing while limiting cross-contaminations (egg products).