ATP Monitoring Fact Sheet (CLICK TO ACCESS FACT SHEET)
Biofilms – Clean Those Surfaces! The Importance of Cleaning
What are biofilms and why should we care? Biofilms sound like they come from outer space but they are a common occurrence in many different environments. They develop in any place where cleaning is incomplete or ineffective. This might be a variety of surfaces, such as living tissues, medical devices, industrial or potable water system piping or natural aquatic systems. In a food service facility, the concerns are many: plumbing, work surfaces, utensils, equipment or floors, walls and ceilings.
In some cases, biofilms are valuable aids in food production. They are essential in the production of vinegar, ethanol, cellulose and industrial applications (textile, laundry, pulp and paper processing); the formation of biofilms results in more effective processing. In too many other cases, however, the presence of biofilms poses a real hazard in food processing. Pathogens, disease causing microorganisms, use biofilms as hiding places where they can survive and grow.
Researchers define biofilms as a colony of ‘primarily polysaccharide (carbohydrates) material’: the film is difficult to see, often microscopic. Thus, the worker might think that cleaning was effective. A wet wiping cloth left on a work surface, not kept clean and stored properly, might smear soil residues, not removing them entirely, allowing the growth of microorganisms. Only sanitizers used in toxic amounts, a practice not allowed by law, might penetrate these films (not always however!). Over time, the biofilm hardens and protects microbes from all but the most diligent cleaning and sanitizing.
Bacteria in these environments have everything they need to survive and multiply: a food source; moisture and ambient warm temperatures. They might survive for long time periods, depending on the type of bacteria and the level of soil on the surface. (Salmonella, for instance, survives for up to 60 days in soil).
Microorganisms have the ability to adapt to their environment, and, once attached to a surface, can survive for long periods. Listeria monocytogenes, Staphylococcus aureus, E. coli, Lactic acid and Bacillus have been documented in biofilms. Listeria has been found in an ice cream – and dairy plant after 7 years. Staphylococcus aureus, E. coli and lactic acid have the ability to form biofilms on surfaces, E. coli at refrigeration temperatures (4 degrees C – 39.2 degrees F.) Staphylococcus aureus and E. Coli have the ability to form slime layers which simulate biofilms and provide shelter for future growth.
Once formed, removal of biofilms require extraordinary efforts, often impractical and unsafe for the food service industry. Over time, merely rinsing a surface will not remove biofilms; scraping will be required. Biofilms are typically alkaline with a high pH, only affected by strong and caustic detergents such as used in a dish machine. Sanitizers are typically not effective at high pH levels and will not effectively penetrate established soil growth. Sodium hypochlorite (bleach) is much more effective at acidic pH ranges of 3-7.5 range; longer contact times, five minutes or longer, would be required to obtain the required kill rate defined by the government rules as a five log reduction. This type of cleaning is simply not practical or safe.
One problem as with any type of cleaning problem, must be the risk of environmental cross contamination, where colonies of bacteria might become air borne or carried by food service workers into other areas of the facility. Biofilms could also lead to food spoilage, reduced shelf life and transmission of pathogens.
Cleaning must be done with great care to prevent recontamination from soiled implements or wiping cloths.
The Importance of Surface Materials: The first step in addressing biofilm reduction involves the selection of easily cleanable, well designed equipment, utensils and surfaces. The surface construction is important since it influences how easily microorganisms can become attached. Every food sanitation program talks about the construction of food contact surfaces: ‘nonabsorbent, non-toxic, light colored, durable and easily cleanable’. A wood cutting board, for instance, cannot be effectively cleaned due to cracks and crevices. (Accordingly, approved use of wood is usually limited to processing low risk non TCS types of foods.)
Even the smoothest most durable food contact surface, however, has microscopic cracks and crevices which will accumulate debris. Research shows that Listeria monocytogenes can attach to, and leave a sanitizer resistant film on glass, polypropylene, rubber and stainless steel.
The Importance of Organized and Effective Cleaning: The second step in biofilm reduction must be an organized and effective cleaning program. This involves training, modeling of required skills and employee practice sessions to gain competency. The correct chemicals must be selected based on the soil residues which require cleaning (read the label directions for safe use). Cleaning equipment (mops, brooms, buckets) must be cleaned following use, and properly stored, to discourage the spread of biofilms throughout the facility. This contamination can occur, either through the air stream or by employees. Cleaning efforts must be monitored and recorded, both to demonstrate compliance as well as positive and negative patterns of behavior. Since continuous cleaning is impractical and unsafe on a food production line, subsequent cleaning must be planned, organized and effective.
Soils left on surfaces during production cannot be continuously cleaned and can create further problems; research shows that proteins left on the equipment begin forming a film within 5-10 seconds after contact. Food processing equipment often requires disassembly for cleaning and sanitizing; this presents the potential for airborne cross contamination. Contrary to popular belief, bacteria have limited movement on surfaces; they create waste products (slime) from their use of soils for energy. The facility infrastructure (floors, walls, ceiling, piping, bends in pipe, rubber seals, conveyor belts, ventilation ducts, fans) will not be as carefully cleaned, creating the potential for bacterial growth and transfer. Research shows that Buna-N (synthetic rubber) and Teflon seals were sites for biofilms and also cause cross contamination.
What is the moral of this blog article story? Cleaning must be done effectively and regularly to prevent the growth of pathogens. The failure to clean often, using a written cleaning program, will inevitably result in sanitation problems. Over and over we read about processors closed for long time periods during to the presence of listeria. It is difficult enough to produce a five log reduction for ready to eat foods without worrying about migration of pathogens into the production area.
Research has demonstrated that, given optimum growth conditions, bacteria will attach to and grow on a great number of materials used in food processing, including stainless steel. Thus it is inevitable that bacterial problems will develop without a proper cleaning program. It is not a matter of whether bacteria will appear but rather, whether they can be controlled using a cleaning program.
Design your program today! Check your professional associations, industry friends or regulatory contacts for advice. There are often free templates which can be adapted to your facility. List the areas which need cleaning – include the frequency of cleaning, the worker to be assigned the task and the equipment and chemicals required for the job.
Read the chemical label to know the safe and effective use; consult with your chemical supplier if you are unsure. There are five major groups of cleaning compounds (degreasers, acids, detergents, abrasives, descalers), each with a specific cleaning application and each with limits for their safe use.
Then give training presenting the cleaning program, allowing your workers a chance to practice doing their assigned tasks. Regularly monitor to be sure the cleaning is done regularly and effectively. Keep written records of your observations.
It is possible to damage surfaces and equipment using the wrong chemical or process. Here are examples. Increasing heat will bake on soil and, in a dish machine, may simply evaporate as steam. Increasing sanitizer levels (beyond legal requirements) will not result in increased kill levels of bacteria. Surfaces such as stainless steel may be damaged, resulting in more problems with biofilms. Some microorganisms develop resistance of sanitizers; if test results show ineffectiveness, try changing sanitizers.
Rinsing will be critical to remove residues of destroyed microorganisms, possible sites for future biofilms. Agle suggests testing both for proper cleaning as well as the presence of cell residues on cleaned surfaces. This suggests the use of ATP and RLU testing. For more information about ATP and RLU, see the following fact sheet from Cornell.
https://cals.cornell.edu/sites/default/files/2024-02/atp-monitoring-fact-sheet-02072024.pdf
References:
‘A Comprehensive Analysis of ATP Tests: Practical Use and Recent Progress in the Total Adenylate Test for the Effective Monitoring of Hygiene’ Mikio Bakke, Journal of Food Protection, V. 85 (7) July, 2022 pp. 1079-1095
‘Unraveling Microbial Biofilms of Importance for Food Microbiology’ Microb. Ecol (2014) V. 68 pp 35-46 Lizziane Kretli Winkelströter, Fernanda Barbosa dos Reis Teixeira, Eliane Pereira Silva , Virgínia Farias Alves, Elaine Cristina Pereira De Martinis
‘Importance of Microbial Biofilms in Food Processing Plants’ Mahendra Pal, Hayat Seid, Oga Karanfil, Tefera Woldemariam and Asefa Deressa, Beverage and Food World V. 40, 2013, pp. 49-50
‘Disinfection of food production areas’ J. T. Holah, Rev. sci. tech. Off. int. Epiz., 1995,14 (2), 343-363
‘Significance of Microbial Biofilms in Food Industry: A Review’ C. Ganesh Kumar, S.K. Anand International Journal of Food Microbiology V. 42 (1998) pp 9–27
‘Biofilms in the Food Industry’ Meredith E. Agle in Biofilms in the Food Environment
Edited by Hans P. Blaschek, Hua H. Wang, Meredith E. Agle Copyright © 2007 by Blackwell Publishing and the Institute of Food Technologists Environment’