Inhibitory effects of sucrose fatty acid esters on survival of Yersinia enterocolitica on eggshell surface and use of blue lake as indicator of bacterial penetration into eggs.

AIMS: To determine the effectiveness of sucrose monolaurate (SML) and sucrose monocaprate (SMC), alone and in combination with ethylenediaminetetraacetic acid (EDTA), propionic acid (PA) or citric acid (CA) in reducing mesophilic aerobic bacteria (MAB) and Yersinia enterocolitica O:9 populations on eggshells and their damage potential on the microstructure of shell cuticle. METHODS AND RESULTS: Uninoculated eggs and eggs submerged in a solution of Y. enterocolitica were immersed in solutions of the various treatments. MAB and Y. enterocolitica counts on the surface of the eggs were carried out before and after treatment. MAB counts decreased less than 2 logs on uninoculated eggshells irrespective of treatment and reductions of 3.2 and 3.0 logs of Y. enterocolitica were obtained with 1000 microg ml(-1) SML plus 0.1% CA or 1000 microg ml(-1) SML plus 600 microg ml(-1) EDTA solutions, respectively. Y. enterocolitica 2/O:9 was recovered from natural microflora. Use of blue lake staining revealed minimal damage to the shells from the washing treatments. CONCLUSIONS: SML and SMC at 1000 microg ml(-1) combined with CA or EDTA could be effective in reducing Y. enterocolitica on eggshells with a minimal risk of later bacterial recontamination. SIGNIFICANCE AND IMPACT OF THE STUDY: Eggs are a recognized vehicle for transmission of Y enterocolitica although a prevalence of only 2.7% was detected in this study. Washing eggs in solutions containing SML or SMC could eliminate Y. enterocolitica contamination of egg shells.

Survival of Yersinia enterocolitica and mesophilic aerobic bacteria on eggshell after washing with hypochlorite and organic acid solutions.

Populations of Yersinia enterocolitica 0:9 and mesophilic aerobic bacteria on the shell of fresh chicken eggs were assessed prior and after washing with 0.75%, 1%, and 3% acetic and lactic acids, 50, 100, and 200 mg/liter (ppm) of chlorine, and water. Highest reductions of mesophilic aerobic bacterial populations (normal flora) on trypticase soy agar were 1.28 and 2.15 log10 cycles with 100 and 200 mg/liter of chlorine, 0.28 and 0.36 log10 cycles with 1% and 3% acetic acid, and 0.70 and 0.71 log10 cycles with 1% and 3% lactic acid, respectively, as compared to the control group. No Salmonella or Yersinia were detected among the natural flora of the eggs. On Y. enterocolitica O:9-inoculated eggs, reductions of 2.66, 2.77, and 2.92 log10 cycles by 50, 100, and 200 mg/liter of chlorine, of 2.47, 2.48, and 2.49 log10 cycles by 0.75%, 1%, and 3% of acetic acid, and of 2.48 and 2.72 log10 cycles with 1% and 3% of lactic acid, respectively, were observed with respect to the control. Organic acids at 3% caused detachment of the surface cuticle of the eggshell. Y. enterocolitica was more sensitive to the wash treatments than the natural microflora. The absence of potentially pathogenic Y. enterocolitica, observed for other fresh foods, should be a norm for fresh eggs sold in retail stores.