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Food Recalls due to Listeria monocytogenes in the News Again

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As we reported earlier Listeria monocytogenes was a major reason for recalls according to “summary of recall cases in Calendar Year 2016”, by the FSIS/USDA, accounting for over 80% of the pathogen recall cases. Currently, this trend is continuing, with many recalls due to L. monocytogenes.

Hillcrest Dairy in Moravia NY

The New York State Department of Agriculture urged consumers in Cayuga County not to consume raw milk cheeses (“Old Fashioned Raw Milk Monterey Jack,” “Horseradish Monterey Jack,” and “Chipotle Adobo Monterey Jack”) made by Ripley Dairy LLC, from Moravia, New York because they might be contaminated with Listeria. The products are packaged in a plastic shrink-wrapped and marked with Hillcrest Dairy name and were made from raw milk.
The NY Department of Agriculture announcement claimed that “A routine sample of the cheese, taken by an inspector from the Division of Milk Control and Dairy Services on August 9, 2017, was subsequently tested by the New York State Food Laboratory and tested positive for Listeria monocytogenes.  On August 11, 2017, the manufacturer was notified of a preliminary positive test result and voluntarily recalled the product from all their customers.  Test results were confirmed on August 17, 2017.  The cheese will be destroyed by the manufacturer.”
 To date, no illnesses associated with this product have been reported to the Department. 

Expresco Foods Inc Montréal, Québec

The U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS/USDA) announced that the company recalled approximately 20,446 pounds of imported, fully cooked chicken skewer products that may be contaminated with Listeria monocytogenes. American authorities found Listeria monocytogenes during a routine foreign shipment inspection.
The recall includes both Expresco and West End Cuisine brand chicken kabobs. Expresco produced the products between Aug. 9 and 15. The products were distributed to retail locations in Arizona, Connecticut, Florida, Illinois, Maryland, Michigan and Texas.  There have been no confirmed reports of adverse reactions due to consumption of these products.

SunOpta, a subsidiary, Sunrise Growers in Kansas

The FDA announces that SunOpta Inc’s subsidiary, Sunrise Growers Inc. is issuing a voluntary recall of frozen organic dark sweet pitted cherry products due to the potential to be contaminated with Listeria monocytogenes.
 
The recall includes frozen organic dark sweet pitted cherry products distributed from Sunrise Grower’s facility in Edwardsville, Kansas on August 10, 2017. The contamination was discovered during routine testing.
Ninety cases of Great Value, Organic Dark Sweet Pitted Cherry products, were recalled.  The products are packaged in 32 ounce printed plastic zip top bags. Some of the products were packaged under Walmart’s Great Value brand. These recalled products were distributed to a customer distribution center in Louisiana and may have been redistributed to stores in Louisiana and Mississippi.  
No illnesses related to the consumption of these products have been reported.

Fair Oaks Farms, LLC, Pleasant Prairie, Wisconsin

The U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS/USDA) announced that the company is recalling approximately 1,134 pounds of fully cooked pork sausage patties that may be contaminated with Listeria monocytogenes. The fully cooked pork sausage patties were produced on August 8, 2017.
The contamination was discovered by Oaks Farms during routine testing. The products were put on hold at a distribution center but inadvertently they were shipped. The products were shipped to distribution and retail locations in Illinois, Iowa, and Wisconsin.
While no adverse reaction was reported, FSIS and the company are concerned that some product may be frozen and in consumers’ freezers.
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Biofilm and food safety: What is important to know?

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Part 2: What are the best control strategies?

Dr. Bassam A. Annous, Eastern Regional Research Center, USDA–ARS–NEA, and Dr. Ruth Eden, BioExpert.
Biofilms are usually formed in a wet environment and in the presence of nutrients.  Once biofilms are formed, the cleaning of the food and food contact surfaces becomes more difficult to remove the extracellular polymeric substances (EPS). Therefore, prevention of biofilm formation, using regularly scheduled cleaning and disinfecting protocols is an important first step in preventing cells from attaching and forming biofilms on surfaces.
High-temperature washing can reduce the need for the physical force required to remove biofilms. Chemical cleaners suspend and dissolve food residues by decreasing surface tension, emulsifying fats, and denaturing proteins. The mechanism by which cleaning agents remove EPS associated with biofilms has not been determined.

Fruit and Vegetable Surfaces

Conventional methods of washing fresh produce with hypochlorite or other sanitizing agents cannot assure microbial safety because they can only achieve 1-2 log reduction. This is because of many enteric pathogens, such as Escherichia coli O157:H7, cause illness at very low infectious doses. For apples, using water, detergents or sanitizing agents, produced a maximum of 3-log (99.9%) reduction in the levels of E. coli. The same treatment using brush washer surprisingly gave less than a 1-log (90%) reduction in E. coli.
A commercial-scale surface pasteurization treatment developed at ERRC (Annous, Burke, and E. Sites), resulted in 4-log (99.99%) reduction in the population of Salmonella Poona on the surface of artificially contaminated cantaloupe. The process involved the immersion of melons in water at 168.8°Fahrenheit for three minutes and then rapidly cooling them. This pasteurization process not only enhances the safety of the fruit but increases the product shelf life by reducing the native microflora that may cause spoilage.

Equipment

Bacterial cells could attach and form biofilms on food processing equipment.  The complexity of processing equipment makes it difficult to remove and/or inactivate the bacterial cells in biofilms on food processing surfaces.  Since it is extremely difficult to remove these biofilms, food processors should prevent biofilm formation in the first place. This could be done by developing and maintaining a thorough sanitation regiment to help prevent a biofilm layer from attaching to equipment surfaces. Product residues due to spills or debris in the facility support bacterial proliferation and subsequent biofilm formation. Consequently, regular removal of food residues is a key to preventing biofilm formation.
Oko, 2013 suggested three important steps to removing biofilm in a food processing facility:
(i)     Cleaning with appropriate sanitizing agents at the required concentrations
(ii)     Allowing enough exposure time at the appropriate temperature
(iii)     Applying mechanical action
This combination is claimed to penetrate and/or remove the biofilm, and thereby to kill the embedded bacterial cells.
An effective cleaning procedure would break up or dissolve EPS allowing sanitizers to gain access to viable bacterial cells. Alkaline cleaners, especially those with chelators like EDTA, are more effective at removing biofilms than acidic cleaners. Bacteria become far more susceptible to sanitizers once the biofilm matrix has been destroyed, certain enzymes have been proven effective in disrupting EPS matrixes, thus allowing for the removal of biofilms. Recently, novel methods that can serve as alternatives to the current methodology for the disinfection of microbial contamination, such as essential oils and bacteriophages have been successfully tested.
Poly ethylene glycol (PEG) has been shown to inhibit protein adsorption and bacterial attachment to surfaces.  Cold plasma was used to deposit PEG-like structures on the surfaces of stainless steel 304 and 316L using 12-crown-4 ether and tri (ethylene glycol) dimethyl ether (triglyme), and ethylene glycol divinyl ether as starting materials.
The plasma modified surfaces significantly reduced biofilm formation by about 80%. When 1% beef hot dog was added to the base medium, biofilm formation on stainless steel 304 was reduced further. Plasma modification of the surfaces did not interfere with the efficacy of cleaning by the chlorinated alkaline detergent.
Newer physical methods of biofilm removal include super-high magnetic fields, ultrasound treatment, high pulsed electrical fields, combined use of high pulsed electrical fields in conjunction with organic acids, and low electrical fields alone or in combination with biocides, such as silver, carbon, platinum, and antibiotics.

Summary

Most bacterial cells in nature exist in biofilms instead of planktonic single cells.  Organic and inorganic material (nutrients) attach to surfaces of food and/or equipment and thus creates a conditioning layer whereby microorganisms attach to. Microbial cells then start secreting EPS that further help in the attachment of the biofilm to the food and food processing surfaces.  The ESP formation acts as a barrier from sanitizing compounds, making the biofilm stronger. Bacterial activity within the biofilm community can be coordinated through cell-to-cell signaling (Quorum sensing).
Biofilm formation is associated with many foodborne outbreaks. As a result, biofilm has become a problem in food industries as it renders its inhabitants resistant to antimicrobial agents and cleaning agents. The growth of biofilms in food processing environments leads to an increased opportunity for microbial contamination of the processed product.  Pathogenic microorganisms in biofilms are the major source of food contaminations.
Biofilms were created by various bacteria on fruit and vegetable surfaces, on various meats, and especially on all types of processing equipment.  Once created the biofilm is very difficult to remove, and offer significant protection to the bacteria residing in it.
Breaking up EPS is important in eliminating the biofilm protection and making the bacterial cells more susceptible to the cleaning sanitizers.  Several novel methods are available to better clean surfaces containing bacteria in biofilms.
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The Papaya Salmonella Outbreak Expands as Number of Victims Triples

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The Recalls

Since our last report on July 23, there have been several additional recalls associated with the outbreak of Salmonella in papayas. On July 26 after many people got sick, Grande Produce issued a recall for its imported papayas from the Carica de Campeche farm in Mexico. This farm seems to be the primary source of the outbreak. 
On August 4, a second papaya recall was issued by Agroson’s LLC, for more than 2,000 boxes of Cavi-brand Maradol Papaya imported from the same Mexican farm. A few days later, a third papaya recall was issued by Freshtex Produce. These papayas sold under the Valery brand were distributed in Illinois.
Carica de Campeche farm produced papayas under the following brands: Caribeña, Cavi, and Valery.
The FDA first recalled the Maradol papayas from the Carica de Campeche farm in Mexico.
 
Carica de Campeche farm under the brand Caribeña: This first recall came after extensive testing and trace back.  Papayas from the Carica de Campeche farm tested positive for Salmonella Kiambu, Salmonella Thompson, Salmonella  Agona,  Salmonella Senftenberg, and Salmonella Gaminara. The Caribeña brand was distributed by Grande Produce between July 10 and 19, 2017.
 
Cavi brand papayas distributed by Agroson’s:  Agroson’s LLC, recalled certain Maradol Papaya Cavi Brand, grown and packed by Carica de Campeche.  The papayas were distributed on July 16-19 and were available to consumers until July 31. No illness has been reported due to the Maradol Papaya Cavi Brand, and the recall was voluntary in cooperation with the FDA.
 
Valery brand distributed by Freshtex: The FDA announced that Freshtex Produce of Alamo, TX was voluntarily recalling “Valery” brand Maradol Papayas grown and packed by Carica de Campeche. The papayas were distributed to the State of Illinois from July 10 to July 13, 2017. No illness has been reported.
The FDA increased its testing to see if papayas from other farms from Mexico could be contaminated. More brands and distributors are expected to be linked to the investigation.

The Outbreak

The CDC found that as of August 9 a total of   141 people were infected with the outbreak strains of Salmonella Kiambu (51) or Salmonella Thompson (90) in 19 states. Among 103 people with available information, 45 (44%) have been hospitalized.
The data from the testing laboratory and from epidemiological investigation indicated that the most likely source of the outbreak was Maradol papayas from Carica de Campeche farm in Mexico.

Why did it Happen?

Papayas from Mexico are being screened at the border for Salmonella since the outbreak in 2011, by a third party laboratory. Only papayas that have tested negative for Salmonella are allowed into the USA.  The question needs to be asked: how was it possible that the contaminated papayas were able to get into the USA?
As shown in our recent post, research indicated that bacteria can attach and colonize on the surfaces of plants, ultimately forming biofilms. Bassam A. Annous 2005  shows Salmonella produces fimbriae and cellulose, commencing biofilm formation, which helps Salmonella attach and colonize on melon and cantaloupe surfaces. Once attached the cells survive better on the surface.
As mentioned in our previous post, the outbreaks can be due to the ability of Salmonella to attach or internalize into fruits.  Survival and multiplication of Salmonella on fresh fruits is considerably increasing once the protective epidermal barrier has been broken.    FSMA is designed to help minimize the risk of illness from foodborne pathogens in fresh fruits, and include requirements for water quality, employee hygiene, and equipment and tool sanitation. However, to date, all these new measures did not prevent the current papaya outbreak.

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Beef Products Recalled due to Possible E. coli O26 Contamination

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The Recall

The Department of Agriculture’s Food Safety and Inspection Service (FSIS-USDA ) announced that Good Food Concepts, LLC., a Colorado Springs, Colorado recalled 1,290 pounds of raw beef products, processed Aug. 3 and Aug. 4, 2017, due to potential contamination with E. coli O26.
The contamination was discovered on Aug 5, 2017, by the company who had notified the FSIS inspection.  A lot of carcasses received from Callicrate Ranch on July 31, 2017, were found to be contaminated with STEC (Shiga toxin producing E. coli) E. coli O26.
Good Food Concepts company and FSIS are concerned that some beef may have been frozen and in consumers’ freezers.

Pathogenic E. coli

The most prevalent strain of E. coli causing recalls and illnesses is E. coli O157:H7. However, there are seven serotypes of E. coli that cause most of the food recalls and diseases, called the Top 7. They include: in addition to O157:H7 also O26, O45, O103, O111, O121, and O145.

E. coli O26

In the recent past, E. coli O26 resulted in several recalls and illnesses.  E. coli O26 is one of the six most common strains of non-O157 E. coli found to cause foodborne illnesses. 
It is difficult to identify in the laboratory the O26, in particular by the new rapid methods, because most laboratories are looking specifically for E. coli O157:H7. However, it is a pathogenic strain that caused disease. E. coli STEC O26 shows that the extensive genetic diversity and pathogenic clonal subgroups can emerge soon.

Disease Symptoms

Symptoms usually begin two to eight days after exposure. People infected with O26 often develop bloody diarrhea, dehydration, and abdominal cramps. Most people recover within a week. However, some patients can develop hemolytic uremic syndrome or HUS. Children and older people, with suppressed immune systems, are more susceptible to HUS.

Recall due to E. coli O26 by Costco in Canada

The Canadian Food Inspection Agency (CFIA) announced a few days ago that Costco Wholesale Canada Ltd. recalled Gold Coast brand Broccettes – Broccoli Florettes due to possible E. coli O26 contamination. The products had been sold in British Columbia, but no illnesses were reported in association with these commodities.

Previous Recalls Due to E. coli

E. coli O26 and O21were found in flour from General Mills. The FDA investigation identified General Mills flour as the source of this outbreak which led to a voluntary recall in May 2016. On September 29, 2016, the CDC reported (https://www.cdc.gov/ecoli/2016/o121-06-16/index.html) that 63 people were infected with the outbreak strains of E. coli O121 and O26 in 24 states. Illnesses started on dates ranging from December 21, 2015, to September 5, 2016. Seventeen ill people were hospitalized, and one person developed the hemolytic-uremic syndrome.

Multistate Outbreak of E. coli O26 Infections Linked to Chipotle Mexican Grill Restaurants

The FDA  and the Centers for Disease Control and Prevention (CDC) along with state and local officials investigated two separate outbreaks of E. coli O26 infections. Both were linked to Chipotle Mexican Grill restaurants in several states
The CDC reports indicated that as of January 27, 2016, a total of 55 people had been infected with the outbreak strain of E. coli O26. Eleven states were involved: California (3), Delaware (1), Illinois (1), Kentucky (1), Maryland (1), Minnesota (2), New York (1), Ohio (3), Oregon (13), Pennsylvania (2), and Washington (27). There have been 21 reported hospitalizations. The majority of these cases were reported from Oregon and Washington during October 2015.
Chipotle Mexican Grill closed 43 restaurants in Washington and Oregon in early November 2015 in response to the initial outbreak. 

National Meat and Provisions Recalls Beef and Veal Products Due To Possible E. Coli O26 Contamination

The FSIS-USDA announced the recall of approximately 2,349 pounds of beef and veal products that may have been contaminated with E. coli O26, on Oct. 14, 2016. The products were shipped to a distributor, as well as hotels, restaurants, and other institutions in Louisiana.
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Biofilm and food safety: What is important to know?

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Dr. Bassam A. Annous, Eastern Regional Research Center, USDA–ARS–NEA, and Dr. Ruth Eden, BioExpert.

Part 1: What are Biofilms?

In nature, most bacteria do not exist as suspended (planktonic-free floating) cells. Bacteria live in a group (mass of bacterial cells) attached to each other and to surfaces, in a biofilm form.
A biofilm is as a complex community of microorganisms, embedded in self-created extracellular polymeric substances (EPS). Therefore, the biofilm is a microbial population adherent to each other and to surfaces or interfaces enclosed in the matrix. In this complex biofilm network of EPS, the bacterial cells perform less as individual cells and more as a collective living system, frequently creating channels to deliver nutrients and water to the cells located inside the biofilm.
Bacteria create biofilm as a protection mechanism, for better survival in the environment. Cells in a biofilm are more resistant to cleaning and disinfection processes in the food industry. The bacteria in the biofilm attaches so firmly to the equipment’s surface that it becomes resistant to conventional sanitation procedures used by the food industry.
Various techniques such as molecular methods, chemical methods, and physical methods have been used to better understand the complex mechanism of biofilm formation, and to get an insight into how to create a process that will eliminate the biofilm formation and/or inactivate cells within the biofilm.
Moisture and nutrients from food (organic and inorganic material) are commonly found on production lines. These two elements bond together to create a conditioning layer. This layer allows for the initial attachment of the bacterial cells to the surface of the layer and the secretion of EPS. The production of ESP enhances the biofilm attachment to the food contact surfaces and protects the cells within the biofilm from the external stresses such as sanitizing agents.

How is Biofilm Formed?

The formation of biofilm can be described as a stepwise process, as shown in Figure 1, consisting of:
  1. Initial reversible attachment of the planktonic (free-floating) bacteria cell to the surface
  2. Irreversible attachment by the production of EPS
  3. Bacteria multiplication and development of biofilm structure
  4. Development of a microcolony covered by mature biofilm, stabilizing the microcolony from environmental stress
  5. Dispersion of cells from the biofilm into the surrounding, and the return of cells to their planktonic form.
 
Figure 1: Formation of biofilm (adapted from Wikimedia , and Firstenberg-Eden et al )
Organisms in a biofilm act less as individual cells and more as a combined living system and are significantly more resistant to environmental stresses such as antibiotics, sanitizers, chemical stress (pH, oxygen) and biocides than their planktonic cells. This increase in resistance to external stresses, as well as a shield against desiccation, is probably due to the presence of the EPS material.
Quorum sensing (cell to cell signaling) has been shown to play a role in biofilm formation, allowing bacteria to display a unified response that benefits the whole population. Research shows that transfer of antibiotic resistance gene is common in the biofilm environment. This transfer happens readily through conjugation or transformation.
Quorum sensing also enhances the ability of bacterial cells within the biofilm to access nutrients and increases their defense mechanism against competing bacteria and environmental stresses.
A recent publication in Cell showed that bacteria residing within biofilm communities could coordinate their behavior through cell-to-cell electrical signaling. Combining experimental data and mathematical modeling point to an extracellular potassium produced in the biofilm as a mechanism of changing the membrane potential of remote cells, thus, directing their motility.
Therefore, cells embedded within the biofilm can not only influence their behavior but influence the behavior of far-away cells through electrical signaling.  A genetic mechanism appears to allow electrically mediated attraction between bacterial species

Why are Biofilms important to Food Safety?

Continual low-level contamination can be caused by biofilm, releasing bacteria, including pathogens and therefore, causing a food safety concern. Bacteria residing in biofilms are more resistant to antimicrobial agents and cleaning agents. Biofilms on processing equipment can reduce the lethality of the process.
Attached cell increased resistance to cleaning chemical because of the protection provided by the EPS layer. The decreased effectiveness of chemicals might also be as a result of cells being in a compact format reducing exposed surfaces that the chemical can make contact with the bacteria.
Product contamination can occur as bacteria detach from the microcolony periodically and can contaminate the processed foods and the lines.  Pathogenic bacteria such as, Listeria, Salmonella, E. coli, or Pseudomonas, can form a multi-species biofilm, which is more stable and resistant to sanitizing agents.
 
Many outbreaks of foodborne disease are associated with biofilm. Research shows that biofilm has become a problem in food industries such as dairy, fish processing, poultry, meat, and Ready-To-Eat foods, because of the residing organisms increased resistance to external stresses.

Biofilm formation on food surfaces

Fruit and vegetable

Research has shown that bacteria can attach, colonize on the surfaces of plants, eventually forming biofilms. The ability of sanitizers to inactivate the bacterial cells in the biofilm is significantly reduced
Disinfection steps by a diverse group of chemicals (e.g., chlorine, peroxide, surfactants, organic acids, etc.), UV, and irradiation were tested without successfully eliminating pathogens in the biofilms formed on fresh produce (without significantly affecting the product quality).  Pathogens that are incorporated into mixed-species biofilms make them less susceptible to antimicrobial treatments as well as increase their tolerance to other stresses such as desiccation and UV.
Biofilms on plant surfaces are composed of a wide variety of bacterial species.  The population dynamics of biofilms vary greatly corresponding to environmental conditions such as temperature, relative humidity, and the availability of nutrients.
Biofilm formation on plant surfaces is probably a survival mechanism for bacteria to endure harsh environment, including desiccation, UV exposure, and temperature fluctuations.
Research data (Bassam A. Annous 2005 ) shows Salmonella produces fimbriae and cellulose, starting biofilm formation, which helps the organism attach and colonize on melon and cantaloupe surfaces. Once attached to the fruit Salmonella cells survive better, and are less susceptible to the harsh sanitizing environment. The organism becomes difficult to remove from the cantaloupe surfaces due to attachment to inaccessible sites and biofilm formation on the cantaloupe rind surface, thus avoiding contact with the sanitizing solution.
After that, the surviving cells can be transferred from the surface of the fruit into the internal tissue of the fruit during processing, presenting a major obstacle for ensuring the microbiological safety of fresh-cut cantaloupe.
The produce most frequently associated with outbreaks include cantaloupe melons, apples (unpasteurized juice or cider), and leafy greens.

Meat

There are meat surfaces to which bacteria attach readily and other meat surfaces to which they attach much slower. The smooth chicken breast muscle (fascia) was the best surface for attachment of all bacteria examined. A linear relation between the concentration of bacteria attached to the surface and time during the attachment process was observed. On some surfaces, this linearity continued for a long time [teats of a cow, chicken breast with fascia, chicken skin]. Bacterial strain also impacts the attachment kinetics.
The bacteria are easily removed in the water film stage. With time, these bacteria could attach to the meat and become difficult to remove due to EPS formation. Brown et.al showed the attachment and biofilm formation by Campylobacter jejuni to extruded chicken meat. They demonstrated that chicken juice contributes to C. jejuni biofilm formation by covering and conditioning inert surfaces and is a source of nutrients. The organism preferentially attached to chicken juice particulates, increasing the attachment rate.
 
Escherichia coli O157:H7 from cattle had the ability to produce biofilm on food contact surfaces such as stainless steel. The attached organisms in the biofilm were able to transfer onto a variety of products such as raw meat, raw poultry, ready-to-eat deli meats, and produce products.
Strains isolated from cattle, retail chicken, and retail beef were able to form strong biofilms in addition to curli fimbriae and EPS production.
Spoilage and/or Pathogenic bacteria can attach to production food contact surfaces, and eventually form a biofilm. The biofilm formation is a major challenge to the meat industry due to the potential of cross-contamination of the meat, causing short-shelf life and/or spread of diseases.

Equipment

Both Gram negative and Gram positive bacteria present on food processing equipment can colonize on stainless steel.  Gram-negative bacteria produced much greater biofilms on stainless steel than Gram positives.
The ability of Listeria monocytogenes to develop biofilms and survive on different types of materials was studied by Wong 2002. The materials studied included two types of stainless steel (304 and 316L), two types of rubber (Buna-N and silicone), and three materials used in conveyor systems (Polyester 3000 and TURE-2 used as belting material, and Delrin, a hard plastic, used in rollers for conveyor belts).
Biofilm formation was best supported by the plastic material Delrin, followed by stainless steel type 304. Food grade silicone rubber and stainless steel type 316L surfaces were the most resistant to biofilm development. L. monocytogenes was capable of forming a biofilm at 10°C, in low nutrient medium on all surfaces tested. The 5-day biofilm cells were more resistant to cleaning and sanitizers as compared to the 2-day biofilms.
The persistence of bacterial cells within a biofilm in the whole food industries including cheeses, dairy products, raw foods, and ready to eat produce continue to contribute to the short shelf-life and/or human pathogenic foodborne outbreak. ESP Material produced by the bacterial cells in biofilms and the complexity of processing equipment makes it difficult to remove and/or inactivate these bacterial cells on food processing surfaces. Therefore, biofilm control relies on the implementation of effective cleaning and sanitizing procedures. Also, the design of processing equipment and the food processing environment that reduces and/or eliminates the accumulation of bacterial and that allows easy, and thorough soil removal can be a significant issue in controlling biofilm formation.
Comming soon our second chapter about Part 2: What are the best control strategies?