Salmonella is a type of bacteria that can cause foodborne illness, leading to symptoms like diarrhea, fever, and stomach cramps after consuming contaminated food or water. The Centers for Disease Control estimates that 1 in every 20,000 eggs are contaminated with Salmonella. Salmonella can infect unbroken eggs inside the shell; the bacteria can originate in the hen’s ovary or oviduct before the shell forms.
Pasteurized Eggs: In Shell and Out of the Shell
Proper handling, storage, and cooking of eggs minimizes the risk that salmonella in eggs will make people sick, but some uses of shelled eggs may not involve cooking to the level required to kill bacteria. Eggs can be pasteurized in and out of the shell. In 2017 less than 3% of eggs were pasteurized. In shell eggs can be pasteurized by various methods, such as:
- Heating
- Irradiation by gamma rays
- Ozonation and mild heating
All the methods add to processing time and cost. Eggs are mainly pasteurized in hot water (130-140 degrees F). Thermal pasteurization can cause the egg whites to denature (cloudiness), color changes in the yolk and impact taste. Ozone and mild heating pasteurization result in an equivalent reduction in bacteria levels while maintaining more of the aesthetic qualities of unpasteurized eggs. The process gained regulatory approval in 2009. This makes ozone-based “in-shell” pasteurization an excellent option.
Ozone Application: In Shell Egg Pasteurization
The process for ozone/heat involves placing the eggs first in a heat bath at 57 degrees C. The eggs are then transferred to a chamber where a vacuum is pulled and followed by pressurization with concentrated ozone, about 10 wt.%. The ozone is pumped out of the enclosure and destroyed. The eggs are removed from the chamber completing the process. The exact temperatures and timing are proprietary.
Perry et al. found that salmonella levels were reduced by >4 logs using the process described above. Kamotani et al. found that consumers’ acceptance of eggs treated with ozone/heat was comparable to the untreated control.
The Ohio State University, Egg Tech Limited, Weaver Brothers Poultry, Hertzfeld Poultry Farms, Hemmelgarn and Sons, Xigent Automation Systems, and the Ohio BioProducts Innovation Center received a grant of nearly $3 MM for the ozone/heat pasteurization process in 2011. In 2017, the Ohio State University received a patent on the process.
A commercial-scale plant is currently under construction. DeNora Capital Controls Ozone was selected as the supplier of the ozone-related equipment. Learn more about our partnership with De Nora.
References:
Perry, J. J., Rodriguez‐Romo, L. A., & Yousef, A. E. (2008). Inactivation of Salmonella enterica serovar enteritidis in shell eggs by sequential application of heat and ozone. Letters in applied Microbiology, 46(6), 620-625.
Kamotani, S., Hooker, N., Smith, S., & Lee, K. (2010). Consumer acceptance of ozone‐treated whole shell eggs. Journal of food science, 75(2), S103-S107.