Listeria monocytogenes in the food industry: where it hides and how to control it through cleaning
Listeria monocytogenes survives in cold, damp environments and forms biofilm in drains, belts and equipment. What makes it hard to eliminate, which areas to monitor and which disinfectants in our range have been tested against Listeria according to their technical data sheets.
Call us: +34 938 891 344 · WhatsApp +34 610 77 61 25
What Listeria monocytogenes is and why it is a concern
Listeria monocytogenes is a bacterium found in soil, water and plants. Unlike most pathogens, it can grow at refrigeration temperatures, so the risk is concentrated in ready-to-eat foods kept chilled: dairy products, cooked meat products, smoked fish or prepared salads.
Listeriosis is rare but serious, especially in pregnant women, newborns, older people and the immunocompromised. Regulation (EC) No 2073/2005 sets microbiological criteria for L. monocytogenes in ready-to-eat foods, and the IFS and BRCGS standards require, depending on the risk, an environmental monitoring programme.
Where it hides in a plant
Drains and gullies
Water, organic residue and little mechanical cleaning: the classic sampling point.
Belts and rollers
Food-contact surfaces with joints and areas that are hard to clean.
Joints, cracks and damaged surfaces
Where soil builds up and detergent and disinfectant do not reach properly.
Cold rooms and evaporators
Cold and condensation: conditions in which Listeria keeps growing.
Equipment that is hard to dismantle
Slicers, peelers, packaging machines: interiors that fall outside daily cleaning.
Standing water
Puddles, poorly sloped floors and dripping hoses.
Biofilm: why disinfecting is not enough
Bacteria that attach to a surface form a biofilm: a layer protected by a matrix that disinfectant penetrates poorly. If you only disinfect, the biofilm recovers. It must first be broken down with detergent action and then disinfected. More detail in the biofilm guide.
Open surfaces
Enzymatic foam
- Enzi Foam — 3–6% at 40–55 ºC, alone or with Enzim Pro at 0.2%
- Enzi Foam Pro — concentrate, 1–3% at 40–55 ºC
Check
Biofilm detection
- Insta Check Pro — sprayed on and, after one minute, effervescence indicates biofilm
Five-step protocol for a risk area
- Remove debris and pre-rinse with low-pressure water, without splashing towards areas already cleaned.
- Clean with an alkaline foam detergent (for example, Gras Foam at 2–6% at 20–60 ºC) or, if verification has detected biofilm, with an enzymatic detergent.
- Rinse to remove the detergent and the loosened soil.
- Disinfect with a disinfectant tested against Listeria, at the dose and contact time on its data sheet (table below).
- Rinse if the data sheet says so, and verify: visual inspection, Insta Check Pro on accessible surfaces and laboratory environmental sampling according to your plan.
Disinfectants tested against Listeria monocytogenes
| Product | Test according to data sheet | Use and dose | Registration no. |
|---|---|---|---|
| Bacter Clor | UNE-EN 13697 at 2%, dirty conditions | Foam, immersion or manual at 2–5%, 5–15 min; rinse with water under pressure | 18-20-06676-HA |
| Clor NF Pro | UNE-EN 13697 at 6%, dirty conditions | Recirculation (CIP) and tunnels, 2–8% at 20–60 ºC, 5–15 min; rinse. Do not use on aluminium | 18-20/40-09617-HA |
| InstaBact® 3000 | UNE-EN 13697, clean conditions | Surfaces and equipment at 2%: 5 min (bactericidal) or 15 min (fungicidal); rinse | 22-20/40-11678-HA |
| InstaBact® DS | UNE-EN 13697, dirty conditions | Ready to use, undiluted, at least 5 min | 20-20/40-10631-HA |
| InstaBact® DS Plus | UNE-EN 13697, clean conditions | Sprayed undiluted on clean surfaces, 5 min (15 min for fungicidal action); single-use paper | 25-20/40/90-12659-HA |
Frequently asked questions
At what temperature does Listeria grow?
Listeria monocytogenes can grow at refrigeration temperatures, which is why it is a risk in chilled ready-to-eat foods and in cold rooms and cold areas of plants.
Which disinfectant kills Listeria?
According to their technical data sheets, the following comply with UNE-EN 13697 against Listeria monocytogenes: Bacter Clor (at 2%, dirty conditions), Clor NF Pro (at 6%, dirty conditions), InstaBact DS, InstaBact DS Plus and InstaBact 3000.
Is disinfecting enough to eliminate Listeria?
Not always: if there is biofilm, the disinfectant does not reach the bacteria properly. You must clean first (with an enzymatic detergent if there is biofilm), rinse and then disinfect.
How do I know if there is biofilm?
With Insta Check Pro: it is sprayed on the surface and, after approximately one minute, effervescence indicates the presence of biofilm. Laboratory sampling confirms whether Listeria is present.
Which areas should be sampled?
Those set by your environmental monitoring plan; the usual points are drains, belts, joints, equipment that is hard to dismantle, cold rooms and areas with standing water.
What do the regulations say about Listeria?
Regulation (EC) No 2073/2005 sets microbiological criteria for Listeria monocytogenes in ready-to-eat foods. IFS and BRCGS require, depending on the risk, an environmental pathogen monitoring programme.
Do you have Listeria positives or want to prevent them?
Tell us what you produce, in which areas the positives appear and how you clean now: we will propose a protocol with detergent, disinfectant, doses and verification.
Request advice
Todos los campos son obligatorios excepto el mensaje.
¿Prefieres hablar directamente? +34 938 891 344
Process guides for the food industry
- Cleaning and disinfection in the food industry
- CIP cleaning: detergents and disinfectants
- Foam cleaning (COP)
- Biofilm: detection and removal
- Step-by-step CIP protocol
- COP protocol for surfaces and utensils
- What CIP cleaning is and how it works
- IFS and BRC standards
- HACCP
- Listeria control
- Cleaning and disinfection plan (template)
- IFS and BRC: cleaning requirements
- Peracetic acid
- Meat industry and abattoirs
- Dairy industry
- Beverages and bottling plants
- Conveyor belt lubricants
- Cold room cleaning
- Dosing calculator