Recent Listeria outbreaks and cheese recalls have renewed concerns about how easily bacteria can persist and spread in food processing environments. Unlike many foodborne pathogens, Listeria monocytogenes can survive and even grow at refrigerated temperatures, making it a particularly difficult challenge for dairy processors and other producers of refrigerated, ready-to-eat foods.
In summer 2026, the FDA and CDC investigated a multi-state outbreak associated with requeson, a soft cheese similar to ricotta. The investigation ultimately included 15 illnesses, 14 hospitalizations, and 1 death. Cheese samples and environmental samples collected from the manufacturing facility tested positive for the outbreak strain, highlighting the important role processing surfaces can play in persistent contamination. The outbreak led to recalls involving multiple cheese varieties, brands, and distributors. Read the FDA outbreak investigation.
Other recent recalls have involved Camembert, Gouda, cheddar, mozzarella, pepper jack, and grated cheese products. These incidents demonstrate that Listeria is not limited to one product, production method, or type of facility. Food processors need multiple layers of protection to control it, including sanitation programs, environmental monitoring, hygienic equipment design, and careful material selection.
Research suggests that coating stainless steel surfaces with Dursan® may provide an additional tool for reducing Listeria biofilm formation on food processing equipment.
Listeria monocytogenes is a disease-causing bacterium found in soil, water, decaying vegetation, and animals. It can enter a food processing facility through raw ingredients, water, equipment, employees, or the surrounding environment.
Once introduced, Listeria may attach to equipment and other surfaces. The bacteria can then form a biofilm, which is a community of microorganisms surrounded by a protective matrix. This matrix helps the bacteria remain attached to the surface and can make them more difficult to remove through routine cleaning.
The ability of Listeria to survive under refrigeration adds to the challenge. Cold temperatures slow the growth of many microorganisms but do not necessarily eliminate Listeria. According to the CDC, even fresh soft cheeses made with pasteurized milk can become contaminated during cheesemaking.
Listeriosis can be especially serious for pregnant women, newborns, adults aged 65 or older, and people with weakened immune systems. For these groups, an infection can lead to hospitalization, pregnancy complications, or death.
Stainless steel is widely used throughout food and dairy processing because it is durable, corrosion resistant, and compatible with many cleaning procedures. However, an uncoated stainless steel surface is not necessarily immune to bacterial attachment.
Scratches, pits, welds, crevices, and areas of higher surface roughness can provide locations where food residue and microorganisms accumulate. Cheese and dairy processing can be particularly challenging because fats, proteins, and other organic materials may remain on equipment surfaces and support bacterial attachment if they are not completely removed.
Moist, difficult-to-access areas can create additional risk. Potential problem areas may include:
Sanitation remains the primary defense against contamination. However, improving the underlying surface may help reduce bacterial adhesion and make equipment easier to maintain as part of a comprehensive food safety program.
Researchers from the University of Massachusetts Lowell and the USDA Agricultural Research Service evaluated how several coatings and surface textures affected Listeria monocytogenes biofilm formation on 304 stainless steel.
The study compared uncoated stainless steel with five coated surfaces, including Dursan. Researchers also evaluated different surface topographies, including machine-finished, brushed, and micropatterned stainless steel.
Biofilm formation was measured using two methods. Crystal violet staining was used to measure the total biomass attached to each surface, while plate counting measured the number of viable bacterial cells.
The crystal violet results showed that Dursan was one of only three coatings associated with statistically lower biomass accumulation. More importantly, the viable cell results showed that Dursan was the only coating tested that reduced active Listeria cells across the different surface topographies. The study reported up to approximately a fourfold reduction in viable cell count compared with uncoated stainless steel.
These findings indicate that surface chemistry, not just visible smoothness, can influence bacterial attachment and biofilm development.
Plate count testing showed the number of viable Listeria cells recovered from each surface. Dursan produced up to approximately a fourfold reduction compared with uncoated stainless steel.
Dursan is a thin, amorphous silicon oxide coating applied using SilcoTek’s chemical vapor deposition process. The coating forms a conformal barrier over stainless steel and other compatible substrates, including complex geometries and internal flow paths.
For food processing applications, Dursan offers several potentially useful surface properties, including a high degree of hydrophobicity that can help reduce surface wetting and unwanted material adhesion:
Dursan is also certified to NSF/ANSI 51 and meets applicable FDA food-contact coating requirements. It is important to distinguish FDA compliance from approval of a complete piece of equipment or process. Food producers should evaluate coated components under their own operating, cleaning, and regulatory conditions.
SilcoTek partnered with the University of Massachussetts and the US Department of Agriculture for this case study on reducing Listeria formation on stainless steel surfaces.
Dursan is not a disinfectant, and a coating cannot replace proper sanitation, environmental monitoring, employee training, or hygienic equipment design. It should be considered an additional surface engineering measure within a broader food safety strategy.
Dursan has also demonstrated stability following autoclave exposure, a sterilization method that uses saturated steam under pressure. In SilcoTek testing, Dursan-coated 316L stainless steel coupons were exposed to temperatures between 121 and 123.2°C for 60 minutes. After exposure, Dursan maintained a high degree of hydrophobicity, with the average water contact angle changing from 88° to 78°. Testing also found no significant loss of coating thickness or visible coating damage. View the complete autoclave test results.
By reducing the number of viable cells able to remain on stainless steel, Dursan may help processors address one of the conditions that allows contamination to persist. Its corrosion resistance may also help protect metal surfaces from pitting and degradation that can create additional sites for residue and bacteria to collect.
Potential applications include food-contact equipment used during cheese production, dairy processing, filling, transfer, sampling, and packaging. Because every process is different, representative parts should be tested under actual exposure and cleaning conditions before the coating is adopted throughout a production system.
Recent cheese-related Listeria incidents demonstrate how contamination within a processing environment can affect numerous products, distributors, retailers, and consumers. Preventing these events requires close attention to every potential point of contact, including the surfaces used to manufacture and transport food.
Research shows that Dursan-coated stainless steel can reduce Listeria biofilm biomass and viable cell counts compared with uncoated stainless steel. When combined with appropriate sanitation and monitoring practices, Dursan may provide food and dairy processors with another way to create cleaner, more resistant product-contact surfaces.
Contact SilcoTek to discuss your food processing components, sanitation conditions, and application requirements.