Where Does Listeria Become Dangerous in the Food Industry?
At first glance, a pack of smoked salmon looks, smells and tastes perfectly normal. Even so, it can carry enough bacteria to make a pregnant woman seriously ill. That is what makes Listeria in the food industry so treacherous. The bacteria are invisible, they tolerate cold and they hide in places that ordinary cleaning misses. However, if you control the cold chain, hygiene and records, you reduce the risk considerably.
What Listeria is
In short, Listeria are rod-shaped bacteria found almost everywhere: in soil, water, on plants and, unfortunately, in food businesses too. The most important species for humans is Listeria monocytogenes. It causes listeriosis, a rare but serious infection.
The tricky part is that you cannot see, smell or taste Listeria. As a result, a contaminated product looks completely normal. In addition, the bacteria can grow at refrigeration temperatures, only more slowly than in the warm.
What EU law requires
The central rule comes from Regulation (EC) No 2073/2005 on microbiological criteria for foodstuffs. Among other things, it sets limits for Listeria monocytogenes in ready-to-eat foods. A key value is 100 colony-forming units per gram (cfu/g) throughout the shelf life of products on the market.
In addition, Regulation (EC) No 852/2004 requires a working food safety system based on HACCP principles. For producers of ready-to-eat foods with a Listeria risk, Regulation 2073/2005 also requires samples from processing areas and equipment.
What changed on 1 July 2026
Commission Regulation (EU) 2024/2895 amending the Listeria criteria in Regulation 2073/2005 has applied since 1 July 2026. It concerns category 1.2: ready-to-eat foods that can support the growth of Listeria and are not intended for infants or special medical purposes.
For these products, the strict criterion "not detected in 25 g" now applies throughout the shelf life. Previously, it applied before the food left the immediate control of the producer. Now it also covers retail and the time until the use-by date.
However, there is one exception. You may still work with the 100 cfu/g limit if you can demonstrate to your competent authority that the product will not exceed it throughout its shelf life. In practice, this usually means shelf-life studies and challenge tests.
For this reason, the European Commission updated its guidance on Listeria shelf-life studies. The Food Safety Authority of Ireland's summary of the new EU Listeria guidance explains what it covers.
Cold slows Listeria, heat kills it
This is the most important point about Listeria. Unlike many other germs, they keep growing in the fridge. Cold therefore slows them down, but it does not stop them.
Heat, by contrast, kills them. A widely used guideline is thorough cooking with at least two minutes at 70 °C in the core of the food. Freezing does not kill Listeria. It only stops growth, which continues after thawing.
Specific storage temperatures depend on the product, the manufacturer's instructions and your own hazard analysis. As a rule of thumb, keep products as cold as practical and never break the cold chain. Independent sensors from the QMSpot sensors and temperature monitoring module help you prove exactly that.
Where the weak spots are
Listeria like damp, cool corners and patient businesses. In practice, the same weak spots come up again and again.
Broken cold chain. Goods stand too long on the loading dock, in a warm delivery area or during restocking.
Cross-contamination. For example, raw and ready-to-eat foods share boards, knives, hands or surfaces.
Biofilms. Listeria settle in drains, seals, door gaskets and slicers and survive superficial cleaning.
Vacuum packs. Listeria also grow without oxygen, so vacuum packing is no protection. Smoked fish is a classic example.
Cleaning equipment. In particular, bacteria multiply quickly in damp cloths and sponges.
Storage that is too long. Teams ignore the use-by date, although bacterial counts rise over time.
In production, environmental monitoring of these places is part of the routine. Our article on hygiene in food manufacturing explains zones and sampling in more detail.
Where it gets really dangerous
Above all, the real danger lies where high-risk foods meet vulnerable people. Typical high-risk foods include smoked and gravlax-style fish, raw milk cheese and soft cheese, minced meat and short-ripened raw sausage. Pre-cut packaged salads, smoothies and sandwiches from the chiller cabinet also belong to this group.
Equally, vulnerable groups include pregnant women and their unborn children, newborns, older people and people with weakened immune systems. For them, listeriosis can be severe. Therefore, kitchens in hospitals, care homes and childcare carry a particularly high responsibility. For these groups, it can make sense to reheat ready-to-eat dishes thoroughly before serving.
What you need to document
Temperature records. Continuous, time-stamped values for every cold spot, ideally from independent sensors.
Cleaning and disinfection. Plans and checks for slicers, drains and seals as digital checklists and inspection plans.
Environmental monitoring. Sampling plan, results and actions after positive findings.
Shelf-life evidence. Shelf-life studies or challenge tests for category 1.2 products.
Training. Instructions on cross-contamination and use-by dates, recorded in the QMSpot training and instructions module.
Recall readiness. A tested procedure for withdrawals and recalls, supported by the QMSpot product recalls module.
Frequently asked questions
At what temperature does Listeria die?
Thorough heating kills Listeria reliably. A widely used guideline is at least two minutes at 70 °C in the core. Freezing is not enough, because it only stops growth.
Does Listeria grow in the fridge?
Yes, and that is exactly what makes it so treacherous. It grows at normal refrigeration temperatures, only more slowly. Short storage times and respecting the use-by date are therefore essential.
Which limit applies to ready-to-eat foods?
Regulation 2073/2005 sets a limit of 100 cfu/g throughout the shelf life for many ready-to-eat foods. For category 1.2 products, "not detected in 25 g" has applied throughout the shelf life since July 2026, unless you can prove the 100 cfu/g limit holds.
Which foods are most affected?
Mainly chilled ready-to-eat products that are not heated again. For example, they include smoked fish, raw milk and soft cheese, minced meat, short-ripened raw sausage and packaged salads, smoothies and sandwiches.
How to get started
Tomorrow, walk through your cold store and chiller cabinets with one question in mind: which ready-to-eat products are not heated again before eating. Then mark them as your high-risk group.
After that, check three things for these products: the temperature records, the cleaning of the equipment they touch and the shelf-life evidence. To see how this comes together in one system, take a look at QMSpot quality management software.
Not sure where Listeria could hide in your business?
Then let's talk briefly about your processes and see how you can control cold chain, cleaning and shelf-life records with QMSpot in a clear and traceable way.