Environmental conditions and molecular fractions involved in the antimicrobial activity of egg white against S. Enteritidis

Abstract

In Europe, the species Salmonella enterica, particularly the serovar S. Enteritidis, represents the major human pathogen related to egg consumption. Consequently, it is mainly used as a model in most studies interested in the antimicrobial activity of egg white. In order to explain this antimicrobial activity, the main hypotheses are, on the one hand, the involvement of antimicrobial egg white proteins (ovotransferrin, lysozyme…), and, on the other hand, physicochemical factors such as alkaline pH, and viscous and heterogeneous structure. However, data are conflicting in the literature, and it is difficult to compare the studies because of the use of various strains, various inoculum sizes, various incubation times and temperatures and eggs with varying freshness.Hence, we have investigated the incubation conditions enhancing the antimicrobial activity of egg white against S. Enteritidis by carrying a complete factorial design analysis comprising 180 experimental conditions. Three different media were chosen in order to evaluate the effect of the macromolecular fraction of egg white: whole egg white, egg white filtrate, and egg white filtrate supplemented with 10 % egg white. The other tested factors were the temperature (37°C to 48°C), pH (9.3 versus 7.8) and initial inoculum size (3 to 8 log cfu.mL-1). This study clearly identified the temperature and the presence of macromolecules as the main factors involved in the bactericidal activity of egg white against S. Enteritidis