New method pasteurises eggs in 20 minutes

Researchers from the US Department of Agriculture (USDA) have developed a faster way to pasteurise raw eggs in-shell without affecting their taste, texture or colour.

Currently in the prototype stage, the pasteurisation process reportedly kills 99.999% of Salmonella injected into raw in-shell eggs in the laboratory. The method has been published in the journal Agricultural Research.

Currently, the only way to pasteurise raw in-shell eggs is to subject them to an hour-long hot water immersion process. When commercialised, the new method would offer a significantly faster alternative.

The new method uses the energy from radio waves - known as radiofrequency (RF) heating - and a brief hot-water bath to kill harmful microbes without lessening the quality of the treated eggs.

The process involves a raw egg being positioned between two electrodes which send radio waves back and forth through it while the egg is slowly rotated. While this happens, it is sprayed with water to offset some of the heat created by the radio waves.

Unlike conventional heating, the radiofrequency heating warms the egg from the inside out. This means the egg yolk, which is heat-tolerant, receives more heat than the heat-sensitive egg white (albumen).

After this, the egg goes into a brief hot-water bath, which helps the yolk retain its heat to complete the pasteurisation. The bath also pasteurises the white without over-processing it.

The method reportedly takes approximately 20 minutes from start to finish - about a third of the time taken using the traditional hot water immersion technique.

Dave Geveke, a chemical engineer with the Agricultural Research Service, says he expects to begin pilot-scale tests this year. Commercial use of the RF method is at least a year away