Food Safety: Biofilm Formation and Removal

Biofilm is not only difficult to detect, it can form just about anywhere in your food processing plant. Ensuring your food plant’s processing equipment is unaffected by this tricky food safety culprit is critical to preventing contamination and costly recalls.

Biofilm is not only difficult to detect, it can form just about anywhere in your food processing plant. Even clean-looking surfaces can be compromised by an invisible layer of biofilm harboring dangerous bacteria and pathogens. Ensuring your food plant’s processing equipment is unaffected by this tricky food safety culprit is critical to preventing contamination and costly recalls.

What is biofilm?

Think of biofilm like plaque on teeth: when you do not brush your teeth for a long period of time, a bacteria coating adheres to your teeth’s surface. The longer this coating is present, the more it hardens and becomes difficult to remove. That’s essentially how biofilm grows on the surfaces of processing equipment.

In the presence of moisture and nutrients — two elements commonly found in food plants — organic and inorganic material begin to bond together, forming a preliminary conditioning layer. As the conditioning layer grows larger, the bacteria begin to secrete extracellular polymeric substances (EPS), which help the biofilm attach to its contact surface. The EPS also acts as a protective barrier from sanitizing agents, which allows the biofilm to get stronger.

If the biofilm’s growth is uninhibited, it attaches so firmly to the equipment’s surface that it becomes resistant to normal sanitation procedures. Biofilm layers are often thin and can contain dangerous pathogens such as:

  • Listeria
  • E-coli
  • Salmonella

Where does biofilm form and how can you tell?

Biofilm is often difficult to detect, especially in the early stages of formation, but food processors should be on the lookout for the following symptoms:

  • A rainbow appearance on stainless steel surfaces
  • Slimy feel on otherwise clean-appearing surfaces
  • Sour or off-odors, which can indicate potential for biofilm formation

However, the only way to definitively confirm the presence of biofilm is to conduct biofilm testing through methods such as:

1. Adenosine triphosphate (ATP) bioluminescence—ATP is the energy molecule stored in all microorganisms. By analyzing ATP levels, you can reveal the presence of living bacteria on equipment surfaces. However, this is a broad test, and often only detects biofilms in the early stages of formation when bacteria is actively searching for nutrients.

2. UV light detection—UV light clearly reveals the presence of organic sediment otherwise invisible to the naked eye.

3. Total organic carbon (TOC) measurement—TOC measurement in food processing settings is most often used to test rinse water after it’s been used to clean equipment or piping. A low TOC measurement helps validate cleaning efficacy.

Be aware that biofilm can form on any type of surface, including stainless steel, concrete, glass and plastic. However, biofilm is most likely to form on rough, penetrable surfaces or on equipment that has scratches, cracks or dents because they provide a viable niche for bacterial growth and are especially difficult to sanitize. Biofilm also tends to form in hard-to-reach places that are not cleaned regularly, such as the underside of conveyor belts.

To best prevent biofilm formation, utilize sanitary equipment design to eliminate any areas that may be difficult to clean. Otherwise, you must regularly remove and inspect parts such as:

  • Gaskets
  • O-Rings
  • Piping

How do you remove biofilm?

Removing biofilm from surfaces is much more difficult than preventing it from forming. Food processors should develop and maintain a thorough sanitation regimen to help prevent a conditioning layer from attaching to equipment surfaces.

Unfortunately, biofilm can develop even after proper sanitation. If you detect biofilm in your food manufacturing plant, be sure follow these five steps for removal:

  1. Dry clean—Before using chemicals, remove as much visible soil as possible by scrubbing, brushing and sweeping the affected surface. However, be careful not to clean so rigorously as to scratch or etch the surface, as this will only create an environment prone to biofilm growth.
  2. Rinse—Rinse equipment using water at 140°F: a temperature best suited for cleaning with low pressure/high volumes after the mechanical action process (scrubbing). High volumes allow a sheeting effect to occur, allowing the detached biomass to drain.
  3. Apply chemical treatment—The proper chemical to use for biofilm removal will depend on the type of food materials used in the food plant. Collaborate with a sanitation provider to determine the optimal combination of chemicals for your food plant. Studies have shown that the most effective chemicals include sodium hypochlorite, iodine and peracetic acid. Allow an extended exposure time (usually at least five minutes) for the chemicals to dissolve the biofilm effectively. Then, scrub and brush the equipment to completely remove all layers of bacteria. Again, be sure to avoid scratching the surface.
  4.  Apply a final rinse—Rinse the equipment once more, following the same temperature guidelines as step two.
  5. Inspect the equipment—Use one of the detection methods mentioned above to confirm you have successfully eliminated the biofilm. Some instances may require multiple rounds of cleaning. The best way to prevent biofilm from forming to is thoroughly sanitize processing equipment between every shift. However, even with stringent sanitation practices in place, inspect equipment surfaces regularly to ensure they are not contaminated by a resilient biofilm

If you’d like to learn more about biofilm in food processing plants, email Jim Oko at [email protected].

About Stellar

Stellar is a fully integrated firm focused on planning, design, pre-construction, construction, refrigeration, mechanical & utility, building envelope, and total operations & maintenance services worldwide. Visit the company's blog at

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