Study finds sous-vide heat can eliminate Salmonella from eggshells

10 Feb 2020 --- A decontamination method using sous-vide cooking was found to be effective in ridding raw eggs from Salmonella enterica serovar Typhimurium (ST), according to a study at Flinders University in South Australia. The method that employed equipment commonly found in commercial kitchens achieved complete decontamination of ST using heat alone. The findings may provide a simple and clean label solution for preventing salmonellosis affecting eggs through surface contamination. The research offers a chemical-free solution for increasing food safety in products that traditionally use raw eggs such as mayonnaise, mousse, eggnog and artisanal ice cream, among others.

Raw eggs provide a uniquely foamy, frothy or meringue texture, rendering them practically indispensable. However, eggshells contaminated with ST is known to be a key cause of foodborne gastroenteritis around the world, with most outbreaks linked to eggs, poultry meat, pork, beef, dairy, nuts and fresh produce.

To address this issue, the Flinders research team developed a decontamination method that removed ST contamination from eggshells without impacting the egg’s usability. The eggs were placed in a sous-vide cooker with the water heated to 134°F (57°C). Decontamination was achieved in just nine minutes without compromising the function of the egg.

A panel of chefs used measurements and acceptability scores to rate the decontaminated eggs. However, there was no significant difference in egg quality or performance as an ingredient when compared with non-treated eggs.

The results were published recently in the journal Foodborne Pathogens and Disease. This is the first study to look at decontamination of ST on the eggshell.

A second study by the Flinders environmental health research team examined the effectiveness of current Australian guidelines that recommend raw egg mayonnaise should be prepared and stored under 41°F (5°C) 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 and around the world.

The researchers found that the survival of ST in mayonnaise is significantly improved at 39°F (4°C) 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,” says Flinders Environmental Health Researcher Thilini Keerthirathne.

“But there is a risk of storing mayonnaise at 98°F (37°C). 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.”

Other natural solutions tackling mayonnaise preservation include Naturex’s XtraBlend RN based on botanicals. The company’s natural solutions to help maintain freshness in lipid emulsions, such as mayonnaise and salad dressings, can be used to replace ethylenediaminetetraacetic acid (EDTA).

Moreover, companies like Corbion are harnessing natural alternatives in the quest to extend shelf life. At Fi Europe 2019, Corbion lauched six new ingredients within its Verdad and PuraQ Arome portfolios. The solutions enhance food safety, stability and flavor profiles across sectors including meat and seafood, bakery, ready-to-eat meals, sauces and dressings. These solutions are marketed as alternatives to ingredients like sorbates and benzoates, helping manufacturers to create stable, safe and flavorful products.

Edited by Missy Green