The project seeks to develop knowledge of Listeria in dairy sites

An ongoing project is working to identify bacteria present in dairy processing environments to assess their effect on Listeria monocytogenes.

Teagasc in Ireland and the University of Veterinary Medicine in Vienna in Austria are collecting samples from dairy processing plants and characterizing microorganisms, with the aim of preventing the presence of harmful pathogens.

The LmRNA project gains an understanding of the response of Listeria monocytogenes to dairy environmental conditions. Mock communities of microorganisms are created in a laboratory to mimic what is found in dairy environments. The role of other microorganisms is being investigated to determine their effect on Listeria monocytogenes.

The food processing environment is not sterile and the presence of certain microorganisms in cheese production may be desirable. During dairy processing, milk components may adsorb onto surfaces promoting binding and biofilm formation.

biofilm formation
The three-year project uses a metagenomics approach, in which researchers investigate the environment’s microbiome, the most prevalent microorganisms and the interactions between those in biofilms. Culture-based methods are used to isolate live bacteria from these environments.

Scientists create Listeria monocytogenes biofilms in the laboratory. They use conditions often found in the dairy sector, including low temperatures, related growth media, flow systems, and surface materials such as stainless steel.

After entering the food processing environment, bacteria begin to form biofilms with a reversible attachment on the surface. Over time, these bacteria produce exogenous polymeric substances (EPS) which give a bond that can only be lost if direct mechanical and chemical action is performed.

Over time, biofilms grow and shed bacterial cells. This spreads bacteria and may become a source of frequent contamination. EPS biofilm acts as a barrier to antimicrobial diffusion, resulting in closed cell protection. The chemical nature of EPS often inactivates the disinfectants and cleaning agents used in the food industry.

The researchers aim to identify targets for antimicrobials, which will lead to improved strategies to prevent the persistence of harmful pathogens in the dairy industry.

Effect of temperature and salt on Listeria
Another study by Spanish scientists looked at listeria in soft pasteurized milk and raw sheep’s milk cheese.

Researchers at the University of Cordoba and the University of Burgos evaluated the effect of storage temperature and salt concentration on Listeria monocytogenes.

The team analyzed the products at a temperature reflecting product cooling at 4°C, and another based on storage at room temperature of 22°C (71°F). The results showed that the bacteria survived better at lower storage temperatures, according to the study, which was published in the journal Food Microbiology.

They found that the low salt concentration in soft cheese did not affect the behavior of microorganisms.

(To sign up for a free subscription to Food Safety News, click here.)

Leave a Reply

%d bloggers like this: