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Simple solution to ensure raw egg safety

breakfast eggs on toast stock image

South Australian researchers have found a simple solution for preventing salmonellosis caused by eggs through surface contamination, helping Australia’s food services industry.

Eggshells contaminated with Salmonella enterica serovar Typhimurium (ST) pose a health risk, but Flinders University researchers have developed a decontamination method that protects the egg’s usability.

Their work, published recently in the journal Foodborne Pathogens and Disease, was the first study to look at eggshell ST decontamination.

The researchers heated eggs for nine minutes in a sous-vide cooker – equipment commonly found in commercial kitchens – with the water heated to 57C. The process was found to have no significant effect on egg quality or performance as an ingredient, when compared with non-treated eggs.

A preview of the paper, ‘A Successful Technique for the Surface Decontamination of Salmonella enterica Serovar Typhimurium Externally Contaminated Whole Shell Eggs Using Common Commercial Kitchen Equipment’ (November 2019) by Thilini Keerthirathne, Kirstin Ross, Howard Fallowfield and Harriet Whiley is online DOI: 10.1089/fpd.2019.2734

… MEANWHILE: A second study by the Flinders environmental health research team has examined the effectiveness of current Australian guidelines recommending raw-egg mayonnaise should be prepared and stored under 5C and adjusted to a pH less than 4.6 or 4.2.

Despite these guidelines, a significant numbers of salmonellosis outbreaks continue to be recorded every year in Australia.

The researchers found that the survival of Salmonella Typhimurium in mayonnaise is significantly improved at 4C and that lower temperatures protected ST from the bactericidal effect of low pH.

“We found that the preparation of mayonnaise at pH 4.2 or less and incubating it at room temperature for at least 24 hours could reduce the incidence of salmonellosis,” said researcher Thilini Keerthirathne.

“But there is a risk of storing mayonnaise at 37C. If the pH is not correctly measured, the warmer temperatures will promote the growth of salmonella. As such it is crucial to ensure the pH of the mayonnaise is at pH 4.2 or less.”

This study, ‘The Combined Effect of pH and Temperature on the Survival of Salmonella enterica Serovar Typhimurium and Implications for the Preparation of Raw Egg Mayonnaise’ (November 2019) by TP Keerthirathne, K Ross, H Fallowfield and H Whiley has been published in Pathogens journal. DOI:10.3390/pathogens8040218

PhD candidate Ms Keerthirathne said these two studies could help curb foodborne salmonellosis outbreaks related to eggs and raw egg products.

In Australia it was estimated that annually there are 4.1 million cases of food-borne illness including 30,000 hospitalisations and 100 fatalities. One of the most prevalent causes of food-borne illness is salmonellosis.

Over the past decade in Australia the incidence of salmonellosis has increased from 40.9 per 100,000 population in 2005 to 71.5 per 100,000 population in 2015. One of the most common sources of salmonellosis has been identified as raw eggs and egg products.

Source: Flinders University