IRELAND/AUSTRIA – Ireland state research agency Teagasc and the University of Veterinary Medicine Vienna in Austria are currently undertaking a project to identify the bacteria present in dairy processing environments to evaluate the impact on Listeria monocytogenes.

Food-processing facilities are required to follow regulations to provide food safety assurance. However, the food-processing environment in general is not sterile, Teagasc said.

In some cases the presence of bacteria can be desired, such as in the cheese production environment, where the composition of microorganisms in the immediate surroundings (the microbiome) can contribute to the characteristics of the product.

Milk components may adsorb to surfaces during the manufacturing of dairy products, promoting adhesion and biofilm formation.

To avoid the occurrence of dangerous diseases, the two universities are collecting samples from dairy processing facilities and characterizing the microorganisms.

Understanding Listeria monocytogenes’ reaction to dairy environment conditions is one of the goals of the LmRNA study. In the lab, fictitious colonies of microbes are being developed to resemble those found in dairy settings.

The researchers are also studying the functions of various microorganisms so as to understand how different microbes may affect Listeria monocytogenes.

They are employing a metagenomics method in the three-year experiment to examine the environment’s microbiome, the most common microbes, and the relationships among those found in biofilms.

Live bacteria are being isolated from these environments using culture-based techniques.

In addition, the scientists are carrying out biofilm formation of Listeria monocytogenes in the lab, leveraging low temperatures, appropriate growth media, flow regimes, and surface materials like stainless steel, all of which are frequently seen in the dairy industry.

Biofilms are the natural state of bacteria in the environment, says Agriland.

After entering a food processing environment, bacteria initiate biofilm formation with a reversible attachment to a surface. Exopolymeric substances (EPS), which are produced over time by these bacteria, provide the attachment that can only be removed through direct mechanical and chemical action.

Biofilms develop and slough off bacterial cells over time. This causes the germs to propagate and could lead to recurrent contamination. The biofilm EPS acts as a barrier for the diffusion of antimicrobials, leading to protection of the enclosed cells.

The chemical makeup of EPS frequently causes sanitizers and cleaning supplies used in the food industry to lose their effectiveness.

Researchers want to find antimicrobial targets so they can develop better methods of preventing hazardous disease persistence in the dairy business.

Effects of storage temperature and salt concentration on Listeria

Reduced salt concentration in soft cheeses has been found to have no effect on the behavior of Listeria monocytogenes, according to another study by Spanish researchers assessing the effects of storage temperature and salt concentration on the microbe.

The study, conducted by researchers from the University of Cordoba and the University of Burgos,  looked at Listeria in soft pasteurized milk and cured raw sheep milk cheeses.

The researchers examined items at two different temperatures: one based on storage at 220C ambient temperature and the other reflecting refrigeration at 40C.

Results showed the bacteria survived better at lower storage temperatures, according to the study published in Food Microbiology.

The study, which was published in Food Microbiology, found that bacteria fared better at lower storage temperatures.

L.monocytogenes is a pathogen of significant public health risk due to a relatively high mortality rate, although its infection rate is low.

The Food Safety Authority of Ireland (FSAI) issued at least six recall notices in the first half of 2022 due to the L. monocytogenes bacterium.

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