Tackling listeria in food production: good hygiene is key

Every year between 20 and 60 people in Finland become ill with listeriosis, which is caused by the Listeria monocytogenes bacterium. Good food hygiene plays a key role in preventing infection.

In the food business, particularly close attention must be paid to cleanliness. Although the complete removal of listeria is often impossible, regular washing and disinfection are essential in the prevention of contamination.  

Thriving where other bacteria don’t

The listeria bacterium lives in habitats where other bacteria don’t thrive–in drains and on floors and equipment, especially where it is cold. Its water activity level is low (0.92), so different surfaces make a very suitable habitat for it. 

The Finnish Food Authority provides general recommendations on its website to combat listeria in food processing. For general hygiene, the main means of protection is preventing listeria growing. The most effective way of doing so is ensuring that areas are cool and dry. The moisture level of areas should be minimised during production, especially where products are being processed. Copious amounts of water should only be used during the washing and disinfection phase, after which the area should be allowed to dry before being used again. The right order of washing can prevent dirt from being transferred from dirty to clean surfaces. 

Hygienically designed, easily maintained surfaces should be used for food production. In particular, it is important to avoid places where dirt can accumulate and where disinfectants can become ineffective, as listeria is protected from mechanical cleansing in such places.

It is also essential for good hygiene standards to train staff to identify and eliminate risk factors. 

Biofilm formation must be prevented

Listeria is a gram-positive bacterium, which means that it does not form spores. It is able to replicate divide at low temperatures and within the pH range 4.6–9.5. 

Based on the EN 13697 standard for surface hygiene testing, newly-formed listeria cells can easily be destroyed by normal disinfectants and disinfection methods.  The concentrations of disinfectants used must comply with the recommendations, and disinfection must be carried out frequently enough. Only clean surfaces can be free from microbes. 

Particularly problematic hygiene problems in food companies are often linked to the formation of biofilm structures on surfaces. Micro-organisms have a natural tendency to attach to surfaces and replicate to form a tightly attached mucous-like surface structure. Biofilms consist of polymer structures called extracellular polymer substances, as well as product residues and mineral deposits of micro-organisms. Typical targets for biofilm formation include floors, drains, filling machines and seals. The formation of biofilms should be prevented, as such structures cannot be destroyed by normal washing programmes. The removal of biofilms requires special heavy-duty cleaning that depends on the area of use and the severity of the biofilm formation. Listeria monocytogenes is a biofilm-forming species.

Kiilto’s specialists are happy to help in selecting detergents and disinfectants and in determining the problem areas in different premises. Through working together, we can ensure high-quality food production and a good level of hygiene for facilities and equipment. 

Kimmo Nurmi

Product Development Manager