Importance of eggshell cuticle composition and maturity for avoiding trans-shell Salmonella contamination in chicken eggs Arantxa Mu ~ noz a , Nazaret Dominguez-Gasca a , Concepci  on Jimenez-Lopez b , Alejandro B. Rodriguez-Navarro a, * a Departmento de Mineralogia y Petrologia, Universidad de Granada, Campus Fuente Nueva s/n, 18071 Granada, Spain b Departmento de Microbiologia, Universidad de Granada, Campus Fuente Nueva s/n, 18071 Granada, Spain article info Article history: Received 30 June 2014 Received in revised form 24 January 2015 Accepted 3 February 2015 Available online 28 February 2015 Keywords: Cuticle Eggshell Food safety Salmonella ATR-FTIR SEM abstract 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 Sal- monella 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. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Hen eggs are a popular and inexpensive source of proteins which are extensively consumed around the world (Nys, Bain, & Van Immerseel, 2011). However, they are also commonly associ- ated to food-poisoning outbreaks due to their contamination with pathogenic bacteria (i.e., Salmonella enteritis). Only in the EU, there is an estimated incidence of over 100.000 cases of salmonellosis per year, that being a serious health problem with an important eco- nomic impact (EFSA., 2009; Gastois et al., 2009; Messens, Grijspeerdt, & Herman, 2005; Solomon et al., 1997). Thus, it is important to take active actions to reduce the risk of such contamination. Contamination of the egg can occur either prior to the oviposition, due to infection of the reproductive organs, in contaminated flocks, and/or during or after the oviposition, by trans-shell penetration, which is considered the prevalent route for bacterial contamination (Board & Tranter, 1995; Gantois et al., 2009; Messens et al., 2005). Cracked eggs or eggs with a poor eggshell quality (which can account for over 6% of total production) can be more easily contaminated with bacteria and pose an important risk to consumers as they need to be downgraded causing important economic losses to producers (Dunn et al., 2010; Hamilton, Hollands, Voisey, & Grunder, 1979; Washburn, 1982). The egg is protected against bacterial contamination by the eggshell and the shell membranes, which if intact, act together as an effective physical barrier against bacterial penetration (Board & Tranter,1995; De Reu et al., 2006; Jonchere et al., 2010). Even if the eggshell integrity is good, the mineral shell is still perforated by many pores that allow gas and water exchange necessary for the developing chick embryo but also possibilities microbial ingress and contamination of the egg content (Hincke, Nys, Gautron, Mann, & Rodríguez-Navarro, 2012). The cuticle, a very thin (up to 12 um) organic layer, coats the eggshell surface and plugs the eggshell pore opening, thus limiting the movement of particles, water and * Corresponding author. Departamento de Mineralogía y Petrología, Universidad de Granada, 18002 Granada, Spain. Tel.: þ34 958240059; fax: þ34 958243368. E-mail addresses: arantxa@ugr.es (A. Mu~ noz), nadoga@ugr.es (N. Dominguez- Gasca), cjl@ugr.es (C. Jimenez-Lopez), anava@ugr.es (A.B. Rodriguez-Navarro). Contents lists available at ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont http://dx.doi.org/10.1016/j.foodcont.2015.02.028 0956-7135/© 2015 Elsevier Ltd. All rights reserved. Food Control 55 (2015) 31e38