Alternative antimicrobial commercial egg washing procedures

Authors: HUDSON, LAUREN - University Of Georgia; HARRISON, MARK - University Of Georgia; Berrang, Mark; Jones, Deana

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2016
Publication Date: 7/1/2016
Citation: Hudson, L., Harrison, M., Berrang, M.E., Jones, D.R. 2016. Alternative antimicrobial commercial egg washing procedures. Journal of Food Protection. 79:1216-1220.

Interpretive Summary: Commercial table egg producers are required by regulation to wash eggs with water that is at least 11.1oC warmer than the eggs in an effort to prevent bacterial penetration of the eggshell. The industry standard is to wash eggs with a high pH antimicrobial chemical at close to 50oC. Heating water requires expenditure on energy. It may be beneficial to the industry to not have to heat wash water if an ambient temperature wash could be designed to provide the antimicrobial characteristics desired. The objective of this study was to test an alternative egg washing method using chlorine (instead of pH 11) and ambient water temperature to kill Salmonella on eggshells. Four egg wash methods were tested: 1. pH 11 at 48.9oC, 2. pH 11 at 20oC, 3. pH 6, 200 ppm chlorine at 48.9oC and 4. pH 6, 200 ppm chlorine at 20oC. Eggs were surface inoculated with Salmonella Enteriditis and Typhimurium, washed with one treatment and then the shells were cultured to determine the number of viable Salmonella cells remaining. All high temperature wash treatment lowered the number of Salmonella recovered. The ambient water wash at pH 6 with chlorine also lowered Salmonella numbers to the same degree. The only treatment that did not dramatically lessen Salmonella numbers compared to a plain water control was the ambient temperature pH 11 treatment. These data suggest that an ambient temperature egg wash method with chlorine may have utility for controlling Salmonella on the surface of table eggs. Further research is needed to confirm that such a method is adequate for commercial egg processors and warrants consideration of changing regulations.

Technical Abstract: Commercial table eggs are washed prior to packaging. Standard wash procedures use an alkaline pH and warm water. If a cool water method could be developed that would still provide a microbiologically safe egg, the industry may save energy costs associated with water heating. Four wash procedures were evaluated for Salmonella reduction: pH 11 at 48.9°C (industry standard); pH 11 at ambient temperature (~20°C); pH 6 at 48.9°C; and pH 6 at ambient temperature. Alkaline washes contained potassium hydroxide-based detergent, while pH 6 washes contained approximately 200 ppm chlorine and a proprietary chlorine-stabilizer (T-128). When eggs were inoculated by immersion in a cell suspension of Salmonella Enteritidis and S. Typhimurium, all treatments resulted in slight and similar reduction of Salmonella numbers (approximately 0.77 log10 reduction in CFU/mL shell emulsion). When eggs were inoculated by droplet on the shell surface, Salmonella counts were reduced by approximately 5 log10 CFU/mL egg shell emulsion reduction when washed with chlorine plus the chlorine stabilizer at both temperatures and with the alkaline wash at the high temperature. The reductions in Salmonella by these treatments were not significantly (p>0.05) different from each other, but were significantly (p<0.05) more than the reduction observed for 20°C alkaline treatment and 20°C control water treatments. Ambient temperature, acidic washes reduced Salmonella contamination to the same degree as the standard pH 11 warm water wash and may be a viable option to reduce cost, increase shelf life, and slow pathogen growth in and on shell eggs.