New Nofima Case Study Highlights the Real-World Challenge of Controlling Listeria monocytogenes
Share
A newly published case study from Nofima - the Norwegian Institute of Food, Fisheries and Aquaculture Research - provides a rare and detailed look into how Listeria monocytogenes can persist in food processing environments, even in facilities with robust cleaning and disinfection programs.
Case study: Møretrø et al. Controlling Listeria monocytogenes in the food processing environment: Lessons learned from a salmon processor associated with outbreaks. International Journal of Food Microbiology. Volume 449, 16 March 2026, 111604 - see link at the bottom of the page.
The study documents an extensive “seek and destroy” investigation at a cold-smoked salmon producer linked to multiple listeriosis outbreaks. Over several months, researchers conducted intensive environmental sampling, applied deep cleaning and disinfection, whole-room hydrogen peroxide treatments, and even prolonged high-temperature heat exposure of equipment. Despite these efforts, the same Listeria strain repeatedly reappeared.
The root cause was ultimately traced to complex equipment components - specifically conveyor belts and rollers within a skinning machine - where bacteria were able to survive deep inside materials and interfaces that conventional sanitation methods could not reliably reach. Only after the complete replacement of the machine did the contamination stop, with no further detections during long-term follow-up.
What this research tells us
This case study reinforces several important realities faced by food processors today:
- Listeria monocytogenes can persist for long periods in hard-to-access niches, even in modern facilities
- Traditional cleaning, chemical disinfection, and heat treatments may be insufficient when equipment design limits access
- Standard surface sampling can miss deeply embedded contamination
- Hygienic design and continuous contamination control are critical for risk reduction
- The authors rightly focus on hygienic equipment design, intensive investigation, and genomic tools as key elements in managing persistent contamination.
Our perspective at Spectral Blue
While this research does not evaluate light-based interventions, we believe it clearly illustrates why the food industry needs additional, next-generation contamination control tools.
Based on our own experiences across multiple food processors in different countries, we see automated, non-chemical approaches - such as Spectral Blue MWHI™ multi-wavelength, high-intensity blue light - as a valuable complement to traditional hygiene programs. When correctly designed and applied, such systems can continuously target exposed surfaces and hard-to-reach areas between cleaning cycles, helping to reduce the risk of persistent contamination establishing itself in the first place.
Every production line is different, and not every machine or layout is suitable for blue light treatment. That is why application-specific evaluation matters.
Tip: Watch our webinar on Listeria control and new EU regulation - recorded June 2025
Want to know if it could work in your facility?
If you are concerned about Listeria risks on specific machines or processing lines, we invite you to contact us. Our team can review your layout and provide an expert opinion - along with a virtual blue light simulation - to assess whether Spectral Blue MWHI could be a practical and effective addition to your contamination control strategy.
Understanding the risk is the first step. Designing smarter, more resilient control systems is the next.
Related articles
- Nofima's study: Controlling Listeria monocytogenes in the food processing environment: Lessons learned from a salmon processor associated with outbreaks
- Nofima chooses Spectral Blue MWHI for laboratory disinfection
- Sushi producer eliminated Listeria contamination at a packing line
- Atria’s laboratory tested Listeria monocytogenes inactivation with Spectral Blue in a biosafety cabinet
