Destruction of Salmonella enteritidis by High pH and Rapid Chilling During Simulated Commercial Egg Processing

Abstract

Shell eggs were inoculated with a double mutant of Salmonella enteritidis (resistant to both nalidixic acid and streptomycin) by dipping the eggs into a sterile poultry fecal slurry inoculated with this organism. The inoculated eggs were washed with either pH 9 or pH 11 washwater at 37.7°C using a small-scale commercial egg washer. Both washed and unwashed eggs were subjected to either rapid or slow chilling. Both internal contents and external surfaces of eggs were examined immediately after: 1) inoculation; 2) washing; and 3) chilling and 30 days storage at 7.2°C. Washwater pH had a significant effect on the survival of S. enteritidis on the surface of the eggs (p <0.001). Significant cross-contamination occurred between inoculated and uninoculated eggs washed at pH 9; 75% of the uninoculated eggs became S. enteritidis -positive on their surface. No cross-contamination occurred at pH 11 between inoculated and uninoculated eggs, and only 8.3% of inoculated eggs were still surface-positive for S. enteritidis. Slow chilling increased the survival of S. enteritidis on the surface of the eggs (p < 0.01) and appeared to permit penetration of S. enteritidis into eggs washed at pH 9.