The effect of neutral electrolyzed water as a disinfectant of eggshells artificially contaminated with <i>Listeria monocytogenes</i>

Abstract

Neutral electrolyzed water (NEW) was tested as a disinfectant against <i>Listeria monocytogenes</i> on the surface of table eggs. Eggs were collected from a single Bovans White flock and were exposed to <i>L. monocytogenes</i>. Artificially contaminated eggs were divided into three different treatment groups: NEW, 2% citric acid solution (CAS), and saline solution (SS). To evaluate the bactericidal effect, the Mexican norm for antimicrobial activity determination protocol was performed. The observed bactericidal effect was compared against those obtained from CAS and SS. Bacterial cells present on the eggshells were quantified. NEW exhibited a significantly higher bactericidal effect than CAS when evaluated on the surfaces of chicken eggshells (6.11 log₁₀CFU/ml reduction in vitro and a 2.18 log₁₀ CFU/egg reduction on eggs vs. 1.06 log₁₀CFU/ml in vitro reduction and 1.74 log₁₀CFU/egg). Additionally, CAS was found to react with the carbonate egg shield, resulting in a loss of cuticle integrity. Mineral content of NEW-treated eggshells was similar to SS-treated eggshells; however, CAS-treated eggshells showed a significant decrease in phosphorous concentration compared to NEW treatment. In this study, we demonstrated the effect of NEW and CAS on the integrity of the <i>L. monocytogenes</i> wall using transmission electron microscopy. To the best of our knowledge, this is the first report of the effect of NEW against <i>L. monocytogenes</i> on eggshells. Our results show that NEW is a viable alternative solution for the disinfection of table eggs that does not affect the cuticle or shell.