Method may help keep raw eggs safe

Eggs are a nutritious food source, but they can also be a source of Salmonella that causes foodborne illness. A team of researchers in Australia developed a method to decontaminate the surface of eggs without affecting the quality of the eggs.

Eggshell contamination with Salmonella enterica serovar Typhimurium is a cause of foodborne salmonellosis outbreaks and current methods of egg pasteurization and decontamination can properties of the egg proteins, according to the authors of a study published in Foodborne Pathogens and Disease.

The researchers turned to the sous vide technique. This involves cooking food in a temperature-controlled water bath. They artificially inoculated the outside of whole eggs with two S. enterica serovar Typhimurium strains and placed them in a sous vide cooker with the water heated to 57°C. The eggs were heat-treated for 30 seconds and 1, 2, 3, 4, 5, 6, 7, 8, and 9 minutes. After conducting a series of tests that examined the safety and quality of the eggs, the researchers determined that treating eggs for 9 minutes in the water bath at 57°C completely decontaminated them and produced eggs that were rated acceptable for quality.

“We found that the preparation of mayonnaise at pH 4.2 or less and incubating it at room temperature for a least 24 hours could reduce the incidence of salmonellosis,” said Thilini Keerthirathne, an environmental health researchers at Flinders University and an author of the study, in a university press release.

The researchers concluded that using the method right before preparing products that contain raw eggs could help reduce salmonellosis. The researchers were based in Australia, and they noted that more work is needed to determine if the method works against other Salmonella strains found in Australia and if it is effective against heat resistance-induced strains of Salmonella. “Future research is needed to examine the potential consequences of this method on shelf life and the permeability of the eggshell membrane, which will be of significance if the eggs were not to be used immediately,” according to the researchers.