39 Sanitization Methods
Learning Outcome
Describe sanitization methods and the effectiveness of each
Why Clean and Sanitize?
Food processing environments that are not adequately cleaned and sanitized can be a source of microorganisms that cause food spoilage and foodborne illness. These microorganisms may be bacteria, moulds, yeast, viruses or parasites.
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When nutrients and moisture are available and when the environment is favourable (suitable pH, temperature and oxygen level), bacteria, moulds and yeast multiply in food. Viruses and parasites survive in food but depend upon a living host (including the human body) to grow and reproduce.
Food spoilage microorganisms reduce shelf life by causing changes in food colour, texture, flavour and/or smell. These changes make the food undesirable or unsuitable for human consumption. Pathogenic microorganisms, which may produce illnesses or illness-causing toxins, do not create any visible changes in food.
Unclean food processing surfaces provide an ideal environment for the growth of microorganisms. When food comes in contact with unclean surfaces, food-spoilage or pathogenic microorganisms can be transferred to the food being processed. This transfer of microorganisms from a contaminated source to a non-contaminated source is called cross-contamination.
For more information on cross-contamination, refer to the following fact sheet:
Proper cleaning and sanitation of equipment, work surfaces and utensils will:
- Remove dirt and/or food material that harbour microorganisms
- Eliminate most bacteria, including pathogens
- Prevent cross-contamination
- Extend shelf life
- Improve food safety
- Increase protection against financial losses.
What’s the Difference?
While the terms are often used interchangeably, cleaning and sanitation have two entirely different purposes.
Cleaning is the removal of unwanted material (commonly called soils) from production equipment and production areas. Removing leftover particles eliminates many microbes, their food source and other physical debris that can contaminate future batches of food. Appropriate cleaning chemicals may be applied manually or mechanically to equipment that remains assembled (clean-in-place) or that is partially or fully disassembled (clean-out-of-place). Most often, a combination of methods is used.
Sanitizing is the treatment of a clean surface with a chemical or physical agent (e.g., heat) to reduce microorganisms that cause disease and/or spoilage to levels considered safe for public health. By definition, sanitizing a food contact surface must reduce the population of specific bacteria by 99.999 per cent (a 5 log kill) in 30 seconds. Non-food contact surfaces require a reduction of 99.9 per cent (a 3-log kill), also within 30 seconds. When microbial populations are reduced to these levels, the surfaces are considered to be microbiologically clean.
Under optimal growing conditions (e.g., food, water, nutrients, and suitable pH, temperature and oxygen level), the population of the surviving bacteria may double every 20 minutes. Therefore, surfaces that are microbiologically clean immediately after cleaning and sanitizing operations may develop high bacterial levels if left undisturbed for a period of time (e.g., overnight). As a general rule, surfaces left for more than four hours must be sanitized again before production resumes.
Undesirable microorganisms (pathogens and/or spoilage-causing organisms) may come from:
- Ingredients (e.g., fruits and vegetables to be processed or packed)
- People (e.g., dirty hands)
- The building (e.g., dirt and condensation dripping from overhead pipes, dirty drains or unclean doorknobs)
- Equipment (e.g., packaging equipment, pallet truck travelling through the building, dirty buttons and switches, or dirty cleaning brushes)
- Improperly stored garbage and product residues
- Non-potable water
- Pools of water on the floor
- Rodents and other pests
- The air (via aerosols)
- Many other sources.
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Biofilm
Incomplete cleaning/sanitation encourages the development of a biofilm, which becomes an ongoing source of bacterial contamination from apparently clean surfaces. Both pathogenic and spoilage microbes can form a biofilm.
A biofilm is a microcolony of bacteria that securely attaches itself to an inert surface using complex polysaccharide-like material. Once formed, a biofilm provides bacteria with an environment that is favourable to their survival while protecting them from flows of liquids, changes in pH or temperature, and chemical cleaners and sanitizers.
Biofilm can form on the surface of hoppers, conveyors, mixers, grinders, fillers or any other surface that is in continuous contact with food. The microcavities of porous surfaces such as elbows, junctions, cracks, and splits are also ideal areas for the accumulation of residues and biofilm-forming bacteria.
Once in place, a biofilm is extremely difficult to remove or sanitize. Removal often requires sophisticated cleaners with oxidizing agents. The best defence against biofilm development is prompt, regular, complete cleaning and sanitation of all food production surfaces.
For more information on Biofilm, reference the following fact sheet:
Chemicals
There is no perfect chemical sanitizer. Effectiveness depends on:
- Sanitizer concentration (too low or too high is ineffective)
- Surface contact exposure time
- Temperature of the sanitizing solution (generally, 21°C to 38°C is considered optimal)
- pH of the water solution (each sanitizer has an optimal pH)
- Cleanliness of the surface to be sanitized (an unclean surface cannot be effectively sanitized
- Water hardness.
Chlorine
Chlorine is the most commonly used sanitizer in food production facilities. The effectiveness of chlorine depends on several factors:
- The amount of turbidity and chemicals (e.g., iron, manganese, hydrogen sulfide and ammonia) in the water that “use up” chlorine
- The concentration of the chlorine solution added
- The time that chlorine is in contact with the surface
- Water temperature
- Water pH.
It is wise to wear protective clothing and eye covering when using chlorine solutions. Also, make sure that the area is well ventilated.
Contact time of two minutes is considered sufficient to reduce pathogen populations to an acceptable level when the surface is free of organic matter. After sanitizing, allow the surface to air dry.
Temperature also affects chlorine effectiveness. Temperatures should be 24°C (72°F) or a little higher (e.g., lukewarm/tepid water). Chlorine is ineffective above temperatures of 46°C. A word of caution: dangerous chlorine gas is released if chlorine is used in hot water.
Water pH level influences the chlorine concentration required for effective sanitation. The optimum pH is 6.5 to 7.0, but chlorine remains effective within a pH of 6.0 to 7.5. If the pH falls below 4.0, dangerous chlorine gas (mustard gas) is produced. Solution pH should be checked after chlorine is added. (pH may be adjusted with commercially available buffers).
Chlorine is relatively unstable, so chlorine solutions gradually lose strength even in covered containers. Fresh solutions must be prepared frequently. Maximum storage life is 24 hours. Always label containers containing chemical solutions.
Chlorine is incompatible with most other chemicals. Do not mix chlorine with detergent cleaners. When mixing chlorine solutions, always add concentrated chlorine to water; never add water to chlorine to avoid possible explosions when mixing chlorine solutions.
Iodine/Iodophors
Iodophors (a mixture of iodine and surfactant) have broad-spectrum activity and are effective against a wide range of bacteria, viruses, yeasts, moulds, fungi and protozoans. Although less affected by organic matter and water hardness than chlorine, iodophors have a limited effective temperature range (24°C-34°C). They are least effective at low temperatures and vaporize at 49°C. They are most effective at low pH (2.5-3.5) levels. Iodophors have 2.5 times the oxidizing power of chlorine, so a lower concentration is required (e.g., 25 ppm). Iodophors can stain and discolour equipment, especially plastics. They are widely used in the meat industry.
Quaternary Ammonium Compounds (Quats)
A diverse class of compounds, “quats” are the only sanitizer group with true residual activity. For this reason, they are often used on floors, walls, drains, and equipment that will remain idle for longer than 24 hours. Because quats contain surfactants, they can be “foamed” onto vertical surfaces. A concentration of 200 ppm at 24°C to 44°C with a contact time of 45 seconds is required for sanitation. Because quats adhere to surfaces, food contact surfaces must be rinsed before use.
Quats are non-corrosive, odourless and non-staining. They are effective on porous surfaces and effective over a wide pH range. Their effectiveness diminishes in hard water. Organic matter moderately affects their efficiency. Quats are effective at killing yeast, mould, E. coli and Salmonella. They are not compatible with common detergent compounds or chlorine sanitizers.
Compared to chlorine, quats are relatively expensive.
Peroxyacetic Acid (PAA)
Peroxyacetic acid is effective against a broad spectrum of coliforms, bacteria, yeast and moulds. It is effective at temperatures from 5°C to 40°C and at a pH up to 8.0. It decomposes to acetic acid (vinegar), water, oxygen and carbon dioxide.
PAA is most commonly used in fresh-cut, further processed, and post-harvest fruit and vegetable flume and wash water systems, especially in applications where high organic matter would significantly decrease the effectiveness of chlorine. Different formulations are designed to be used directly on whole and processed fruit and vegetable surfaces, on food and non-food contact surfaces, and in clean-in-place (CIP) systems. Rinsing is generally not required.
Peroxyacetic acid can be very expensive.
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Cleaning and Sanitation Methodology
Because sanitizing requires direct contact between the sanitizer and the microorganisms to be killed, surfaces must be clean before a sanitizing solution is used. The presence of organic matter significantly reduces the killing power of sanitizing solutions.
The following steps are required for cleaning and sanitizing:
- Remove/cover food, ingredients and packaging materials from the area to be cleaned. Cover electrical equipment and other equipment that could be damaged by water.
- Using brooms, shovels, squeegees, etc., physically remove as much soil and other debris as possible from equipment, utensils, preparation areas and floors. Place in clearly marked “inedible” containers for prompt disposal. In addition to reducing water usage, “dry” cleaning will reduce the risk of cross-contamination caused by water overspray and lessen opportunities for high-risk drain pooling and backups.Disassemble equipment, as required. Do not place disassembled food contact surface equipment on the floor. Even if it is cleaned and sanitized before reassembly, its floor “storage” location may prevent complete sanitation. Clean, dedicated carts or racks should be provided to clean and sanitize or to transport disassembled pieces to appropriate soak or circulation tanks for cleaning and sanitizing.
- Using 43°C to 50°C potable water, rinse walls from the top down, equipment from the top down and in the direction of product flow, and floors. Don’t forget the underside of counters, tables, belts, etc. and other cracks and crevices where soil may be hidden. Use the lowest effective water pressure (increase volume to compensate for decreased pressure) to reduce the risk of cross-contamination caused by aerosols and oversprays. Excessive pressure may also cause machine damage. Where conditions require higher pressures to remove surface soils, high-pressure sprays must be limited to this step during cleaning procedures. Following this step, walls, equipment and floors should look clean.
- Apply cleaning agents to loosen any remaining “invisible” soil and keep it in suspension. Apply to walls, floors and equipment, in that order, at the correct concentration and temperature. This will reduce the potential for cross-contamination and prevent detergent from drying on equipment surfaces. Cleaning solution must be applied to every square centimetre of surface, including all food contact surfaces and undersurfaces.Every cleaning agent has an optimum concentration level at which soil removal is most efficient. A concentration that is too high is as ineffective as a chemical concentration that is too low. Always follow the manufacturer’s directions carefully.It is generally assumed that the hotter the water used in cleaning, the better the cleaning job. This is true only to a point. A water temperature between 43°C and 50°C is best for efficient cleaning. Water that is too hot may cook the soils onto the surface.Generally, the longer the contact time of the chemical cleaning agent on the surface being cleaned, the better. Check manufacturer’s instructions for minimum exposure time.Some surfaces may require extra scrubbing. Manual cleaning may include using brushes or other hand-operated equipment to remove soil from surfaces. Cloths and sponges can harbour and spread microorganisms from one area to another, so their use should be avoided. Abrasive materials (e.g., steel wool) may scratch surfaces, leading to eventual corrosion. Abrasive materials may also leave behind tiny metal particles that could end up in the food. Clean, sanitized nylon scouring pads may be used instead. Brushes and brooms with food-grade plastic handles and bristles may be used. Squeegees may be used on floors and walls but must be constructed of materials acceptable to the CFIA (e.g., food-grade plastic).Mechanical cleaning may include water hoses with a spray head, pressure spray devices (high or low pressure using hot or cold water) or steam guns. High-pressure water should be used only after preliminary cleaning has been completed in order to lessen the possibility of contamination by aerosols caused when high-pressure water hits contaminated surfaces.
Using foaming solutions means that cleaning solutions will stick to vertical surfaces. Foam should be applied from the bottom up and rinsed off from the top down.
Closed systems require turbulent flow of water, cleaning agents, water, sanitizing agents and water (in that order) through pumps, valves, connections, pipes and tanks. This is described as clean-in-place (CIP). The optimum water temperature is usually 60°C.
Some equipment must be taken apart for cleaning and sanitation. Clean-out-of-place (COP) requires a soak or circulation tank, which comprises four compartments. Disassembled equipment and utensils are soaked/rinsed in the first compartment, manually cleaned with a cleaning compound in at least 43°C solution in the second, rinsed in the third in 43°C to 50°C water, and sanitized in the fourth with either chemical sanitizers or 77°C water for 45 seconds. In a circulation tank, the velocity of recirculating water, combined with chemical cleaners, cleans equipment parts and utensils. Where three compartment tanks are used, initial cleaning must be “dry.”
- Even on vertical surfaces, minute amounts of cleaner may remain after cleaning. (Cleaners are formulated to “stick” to surfaces.) Thorough rinsing carries away the remaining soil (a biological contamination risk) and the cleaning agent (a chemical contamination risk). Use the lowest effective pressure and volume to avoid aerosols and oversprays. Rinse walls first (from the top down) followed by the floor and drains, with equipment and food contact surfaces (from the top down and in the direction of product flow to keep track of what has been rinsed) last. This order will avoid the potential risk of overspray or splashing on equipment that is considered clean. As noted above, only potable water must be used.
- Before reassembling equipment, someone not involved in the actual cleaning should conduct a organoleptic (sight and smell) inspection to check that walls, equipment, utensils, food contact surfaces and undersurfaces, floors, and all nooks and crannies are clean. Use of a flashlight may be helpful. Areas that are not completely clean must be cleaned and rinsed again.
- Much of the floor probably will be covered with cleaner when equipment is cleaned. However, it may be necessary to scrub areas that have been missed. Allow cleaning agents to stand for an appropriate time, then rinse. Don’t forget to remove drain covers and to clean inside drains (see “Important Considerations,” below). Be careful not to use excessive water pressure that may create equipment-contaminating aerosols.
- Apply sanitizing solution at the correct concentration, the correct temperature, and for the appropriate contact time to floors first. Then move to equipment, beginning with support structures and working upward until all surfaces are completely covered. As with cleaners, sanitize in the direction of product flow to keep track of what has been done.After the use of some sanitizers and certain concentrations of others, rinsing with potable water is necessary. Rinsing normally eliminates all traces of chemical sanitizers, but only when all surfaces are flushed with a sufficient volume of water.Hot water sanitizing is commonly used where immersion of the contact surfaces is practical (e.g., small parts, utensils). Depending upon the application, immersion may last from 45 seconds to 5 minutes at temperatures from 77°C to 85°C.A 45-second immersion in 77°C water is equivalent to immersion in:
- A 100 ppm chlorine solution for 45 seconds
- A 20 ppm quaternary ammonium solution for 45 seconds
- A 25 ppm iodine solution for 45 seconds.
- After rinsing, the surface should be air dried to eliminate chemical odours. Drying should be as swift as possible to discourage microbial growth. In some areas (e.g., belt surfaces, floors), it may be necessary to squeegee off water to speed the drying process. Surfaces should never be dried with a cloth or towel that can contaminate the freshly sanitized surface with microbes. Sophisticated operations may lower the relative humidity in the facility so water evaporates more quickly.Food processors may wish to conduct microbiological tests (via environmental swabs) to confirm that food contact surfaces are free from harmful microorganisms.
- “If you don’t write it down, it didn’t happen.” As part of the Sanitation Standard Operating Procedure (SSOP), a record indicating completion of cleaning and sanitation activities should be kept. Deviations from prescribed practices and other irregularities should also be noted, as should the corrective actions taken.
Important Considerations
It is important to understand that sanitation is a sequence of steps with each step building upon the successful completion of the previous step. To prevent potential cross-contamination, each step must be fully complete before the next step occurs. For example, if one sanitation worker is performing a pre-rinse procedure on a machine beside another machine where another worker is doing a final rinse, there is risk that an overspray from the dirty machine may contaminate the clean, sanitary surface of the cleaned machine.
The warmer the temperature, the faster microbes grow and reproduce, and the more frequent the requirement for cleaning and sanitation. As a rule of thumb, for every 6°C (10°F) rise in food ingredient or food product temperature, the rate of microbial growth increases by 50 per cent. For example, at 16°C (60°F), the rate of microbial growth in food debris in a processing plant is 50 per cent greater than if the temperature is 10°C (50°F). The vast majority of human pathogens grow best at temperatures of 25°C to 40°C. (The human body is 37°C.) It should be noted that E. coli grow at temperatures as low as 10°C; Salmonella at temperatures as low as 7°C and the spoilage bacteria Pseudomonas as low as 4°C. A microbiological monitoring program can be used to determine the period of time necessary between cleanups.
Pay special attention to areas where trapped food and water create ideal growing conditions for microorganisms. These include cracks in floors, pools of standing water, clogged floor drains, tape used for temporary repairs, exposed insulation, open-design conveyor belts, the underside of conveyor belts, hollow rollers, fixed sleeved assemblies, concave surfaces and crannies, and crevices in poorly designed manufacturing equipment. Each of these areas can provide an environment in which bacteria (including pathogens, if they are present) can survive and grow.
Drains are an especially high-risk area because they provide an ideal environment for the growth of the pathogen Listeria monocytogenes. To discourage Listeria growth, clean drain covers and the inside of drains on a regular schedule. Sanitation personnel who handle drain components should be prohibited from cleaning food contact surfaces or equipment until protective clothing has been replaced, footwear has been cleaned and sanitized, hands have been washed and gloves replaced.
As with personnel, sanitation tools should be limited to specific functions. To ensure that this happens, colour-coded tools should be used. For example, one colour should be dedicated to food contact areas, another to non-food contact areas, and a third for cleaning drains and other similar areas.
Aerosols created by high-pressure/low-volume water cleaning can be a source of cross-contamination by carrying microorganisms from non-food contact surfaces to food contact surfaces. Whenever possible, do not use high-pressure air or water to clean food processing and food storage areas. Where pressure sprays cannot be avoided, take care to create as few aerosols as possible. Pressure sprays should never be used as a final rinse because any resulting cross-contamination will negate previous cleaning and sanitation.
Certain items require special cleaning and sanitation methods. For example, dirty control buttons can transfer microorganisms to hands, which, in turn, contaminate food, ingredients, food contact surfaces or packaging. Because control buttons are covered for worker safety during cleaning, a safe, effective cleaning and sanitation method must be developed for them. Another example is that only one side of screens may be readily accessible for cleaning and sanitation. This may create a potential area of cross-contamination. In this case, develop procedures to remove screens or to partially dismantle equipment to enable complete cleaning and sanitation. Water and/or chemicals may penetrate sealed surfaces such as bearings if they are cleaned and sanitized improperly. In addition to causing premature wear, penetration may create an entrance for microbes and provide an inaccessible niche for microbial growth.
Applying sanitizer at too low a level or for an insufficient period of time can lead to higher bacterial levels and/or to development of resistant strains of microbes. When this occurs, the area must be “shocked” back to a safe bacterial level by switching to high concentrations of another sanitizer for several days.
A good pest control program is necessary for a cleaning and sanitation program to be effective. Pests, including birds, mice, rats and insects (e.g., flies, cockroaches), can contaminate a food processing facility with urine and droppings, can damage packaging supplies with their gnawing, and can spread a variety of pathogens as they move around the building, equipment and food contact surfaces. Even areas that have been cleaned and sanitized can be recontaminated.
For a summary of sanitation, refer to the following fact sheet:
Sourced from “Foods of Plant Origin Cleaning and Sanitation Guidebook” © QUEEN’S PRINTER FOR ONTARIO, 2016, in accordance with terms of use, accessable at: http://omafra.gov.on.ca/english/food/inspection/fruitveg/sanitation_guide/cs-guidebook.htm