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From: Food Quality & Safety magazine, October/November 2013

Keep It Clean

by Kevin Keener

Keep It Clean

The Virtual Food Systems Training Consortium (VFSTC) is a coalition of four universities that is creating online training for food inspectors from federal, state, local, territorial, and tribal agencies. Inspectors of FDA-regulated foods will be able to get up-to-date training without taking time away from work and costing already-strapped states a lot of money. As the “subject matter expert” for two online courses about sanitation, I am detailing the best practices that inspectors of FDA-regulated foods will be looking for when they inspect a food procesing facility.

The Food Safety Modernization Act (FSMA) gives the FDA increased regulatory authority, and there is a good possibility that new regulations might require written hazard-control plans for food production facilities that have not required such plans in the past. FSMA includes an exemption based on income and sales, but recent discussions with state regulators suggest many states will implement regulations requiring small, exempt processors to meet the federal requirements.

Some of the regulations that will define the law are still a big question mark, but it might be a good idea to look at your current procedures, and companies that do not have a hazard analysis plan in place should get ready to implement a written plan. FSMA’s main emphases are prevention, inspection and compliance, response, and imports. Under “prevention,” you will have to evaluate hazards and then identify preventative steps and controls to reduce those hazards, which means you need to know the basics of disinfection.

The Cleanup

Cleaning is the physical removal of visible soil from surfaces, kind of a “touch-up.” But remember—just because a surface appears clean, it might still be teeming with microorganisms. Sanitizing, then, is the treatment of a surface to significantly reduce the number of microorganisms. What we call “sanitation” is a combination of the two.

Figure 1 illustrates the objectives in each step of the sanitation process. We are looking at the remaining soil and bacteria attached to a food contact surface, with the understanding that the initial “dry” clean and rinsing steps have already been completed. On the far left, notice the bacteria in the white area being protected beneath the overlying layer of soil. Once a cleaning agent is applied, along with some mechanical action and/or time and temperature requirements, followed by another rinse, we now see the removal of the soil along with a significant portion of the microbe population.

This first step, cleaning, is extremely important and removes approximately 90 percent of all microbes on a surface. After cleaning the processing equipment, floors, and walls, all visible traces of soils and contamination have been removed—but invisible microorganisms tightly adhering to equipment areas and surrounding surfaces still pose a contamination risk. These surfaces must be disinfected to kill all microbial populations.

Figure 1
Figure 1

The Role of Disinfectants

Sanitizers are the last line of defense against pathogens in a food manufacturing facility; when a sanitizer is applied to the surface after cleaning, the microbe population is reduced even more to a very low, safe, acceptable level, providing a surface nearly free of microbial contamination. Basically, disinfection is the process of destroying pathogens, their toxins, and associated vectors via heat, chemical treatments, or ionizing radiation. The disinfectant is the agent that delivers the disinfection.

The FDA defines sanitization as “the application of cumulative heat or chemicals on cleaned food-contact surfaces that, when evaluated for efficacy, is sufficient to yield a reduction of 5 logs, which is equal to a 99.999 percent reduction of representative disease microorganisms of public health significance.” FDA regulates chemical sanitizers as an indirect food additive and includes conditions of use specifications.

There are three commonly used methods of sanitation: Thermal, radiation, and chemical. The Environmental Protection Agency (EPA) regulates sanitizers for all applications, from health care to food manufacturing. To be an EPA-registered sanitizer (whether thermal, radiation, or chemical) for a food contact surface, test results for a product must show a bacterial reduction of at least 99.999 percent over the parallel control count within 30 seconds for the bacteria E. coli and S. aureus.

Obviously this is a big subject, so I am going to focus on chemical disinfection, a very common and effective way to sanitize equipment or other surfaces. Chemical sanitizers to be used on previously cleaned food contact surfaces require a 5-log reduction of S. aureus and E. coli and are registered by EPA for efficacy.

Sanitizing Solutions

A sanitizing solution consists of a chemical compound that is mixed with water and applied to a surface. This chemical attacks and kills microorganisms present on the contact surfaces. The most common chemical compounds utilized as effective sanitizers are chlorine, iodine, quaternary ammonium (known as “QUATS”), and peroxide.

Chemical sanitizers available for use in food processing vary in their chemical composition and their activity, and understanding the individual characteristics of each chemical is the key in choosing the best sanitizer for a particular job. The ideal sanitizer has broad-spectrum microbial destruction properties, with a uniform rapid kill against vegetative bacteria, yeasts, and molds. It must also be effective in the presence of organic matter, detergent residues, water hardness, and pH variability.

The ideal sanitizer is also nontoxic and nonirritating, soluble in water, noncorrosive, has a low level of acceptable odor or is odorless, and is stable in both its concentrated form or at its diluted usage level. Application methods vary from product to product, and recommended directions for use are listed on each sanitizing product. Sanitizers should be easy-to-use, readily available, and inexpensive.

Chlorine Sanitizers. These sanitizers are commonly utilized in the food industry because they are inexpensive, fast acting, and effective against a variety of microorganisms. There are several different chlorine compounds that are used, including hypochlorite, organic and inorganic chloramines, and chlorine dioxide. Chloramines are formed from the addition of ammonia to hypochlorous acid, forming chloramine and water.

The term “available” or “free” chlorine is used in evaluating a chlorine sanitizer’s level of effectiveness. “Free chlorine” is the amount of chlorine available to act as a sanitizer. One thing to remember, however, is that chlorine will bind to organic soils or evaporate and, as a result, becomes unavailable in the sanitation process. For example, residual soap will negate a chlorine solution’s sanitizing effectiveness, underscoring the importance of the cleaning process that precedes the disinfection process.

Municipalities that treat drinking water with chlorine target a minimum residual of 1 part per million, or ppm, of free chlorine. Most public spas and hot tubs must contain 1.5 to 3 ppm of free chlorine. In the food industry, a chlorine solution of 50 ppm or less is not considered a sanitizer, so 50 ppm of chlorine is the minimum requirement imposed on a sanitizer for a food facility. But remember—too high a concentration of free chlorine results in chlorine residues. Therefore, generally, the maximum usage level for equipment (without rinsing) is 200 ppm.

Chlorine efficacy is both temperature and pH-sensitive. At high water temperatures, chlorine quickly evaporates, rendering the solution ineffective. The pH also affects a chlorine solution’s efficacy, with chlorine solutions being most effective at pH levels around 6.5. At a lower pH, the chlorine solution can be corrosive to materials and surfaces. Chlorine’s effectiveness drops very quickly as pH rises above neutral pH of 7. Because chlorine is corrosive and a skin irritant, its use poses potential health hazards.

Iodine Sanitizers. The most effective iodine-containing compounds used in the food processing industry are iodophors. Iodine sanitizers are effective against most microorganisms, including bacteria, yeasts, and molds at a usage level of 12.5 to 25 ppm. Unlike chlorine, iodophors are effective under a wide pH range (pH 2 to 10); however, they are primarily utilized under low-pH conditions (in the acidic range). Remaining soil on surfaces will quickly bind chlorine, making it ineffective. Therefore, iodine sanitizers are more stable where there is residual soil in the environment.

The advantages to iodine sanitizers are that they can be used at much lower pH levels and that they are less corrosive than chlorine. The efficacy of iodine sanitizers is temperature dependent, however. At high temperatures (above 80 degrees Celsius), iodine becomes very corrosive. At temperatures below 50 degrees Celsius, it is unstable and ineffective.

The disadvantage to iodine sanitizers—and it is a big one—is that iodine sanitizers are two to four times more costly than chlorine sanitizers, depending on the formulation. Another drawback is that the significant contact or residence time required for an effective microbial kill is longer (up to 30 minutes). In addition, iodine sanitizers have an odor that some people find unacceptable, and iodine solutions can stain, leaving equipment surfaces yellow or orange.

QUATS. The QUATS family of tertiary amines is identified in part by its different chemical side groups. A variety of QUATS are available for use in the food processing industry, but bromine or chloride types are the most commonly utilized. QUATS readily adhere to the surface of microorganisms and are considered to be the most efficient and effective sanitizers used in the food industry. They are very effective in killing bacteria over a wide pH range (pH 6 to 10) and under high temperatures, at a usage level of 150 to 200 ppm.

One advantage to using QUATS is that they are odorless, unlike chlorine and iodine sanitizers. Also unlike chlorine and iodine sanitizers under similar pH conditions, they are noncorrosive. Disadvantages with QUATS are they are sensitive to hard water conditions, they have poor efficacy at low temperatures, and they are ineffective against spores and may support the growth of pseudomonas (spoilage bacteria). QUATS generally are two to four times more expensive than chlorine disinfectants.

Peroxide. Peroxyacetic acid (PAA) has become a popular sanitizer in the food industry. This sanitizer has an effective usage level between 100 to 250 ppm. Advantages are that this sanitizer generates little foam and is effective against a broad microbial spectrum, including bacteria, yeasts, and molds. In addition, PAA is fast-acting and pH tolerant. It is also effective over a wide range of temperatures and under hard water conditions, as well as being nonreactive with organic soils such as

fats and proteins. It is environmentally friendly and breaks down into acetic acid (vinegar), oxygen, and water. The disadvantages are that PAA does have a strong odor and becomes ineffective above pH 8.0. PAA is three to five times more expensive than chlorine.

Which Disinfectant to Use

The Code of Federal Regulations (CFR) contains requirements for sanitizing different kinds of operations. For example, 21 CFR 129.80 (d) includes a number of sanitizer options for sanitizing bottled water operations. These are all disinfectants and meet sanitizing requirements. Many times the selection of a specific sanitizer is determined by water chemistry, costs, and operational activities. If steam is available, it is a very effective and low-cost sanitizer; when steam is not available because of equipment complexity or facility limitations, many other chemical alternatives exists.

The chemical alternative is generally selected to minimize the impact on product quality. For example, a bottled water plant one will typical use a 0.1 ppm ozonated water over a 50 ppm chlorine solution because the residue from a chlorine solution may impart an objectionable taste even at levels as low as 1 ppm. Some facilities find that alternating between two different disinfectant types (such as a chlorine and a QUATS) allows better control of spoilage organisms.

Environmental considerations may come into play when choosing a chemical disinfectant. Wastewater discharge requirements, the level of wastewater treatment capacity at the facility, pH, water temperature, and water chemistry management may factor into the decision.

Deciding between so many possible disinfectants might seem difficult unless sanitation is your full-time job, but there are plenty of suppliers that can help you identify the right product type and the most appropriate level for your water type, pH, temperature, and equipment type.

Factors Involved in Selecting Sanitizer
click for large version

Verification with ATP

After cleaning and sanitizing is complete, how do company personnel know equipment and other surfaces are indeed clean and sanitary? Verification is absolutely the most critical part of a sanitation plan and should never be skipped, no matter how small the operation. In fact, small operations are at higher risk for bacterial contamination of equipment, which can affect the product and be passed on to the consumer. A company can be ruined if a product is recalled or, worse yet, people get sick from a foodborne illness.

First, start with a visual inspection immediately after cleaning. Surface contamination must be removed along with the residual cleaner. Lighting in some facilities is not always optimal, so visual inspection should be performed with a flashlight, a spotlight, or even a black light. This serves as a daily “check.”

Periodically, a rapid chemical test using adenosine triphosphate (ATP) bioluminescence should be performed to verify clean conditions prior to sanitizing. This commercially available rapid swab test measures the amount of organic matter remaining on a surface by detecting the amount of ATP in the organic matter. ATP is a vital energy source that microbes easily store and utilize for cellular functions. The amount of ATP—and where it is located—alerts company personnel to possible trouble spots that might need to be re-sanitized before starting the next production cycle.

A sanitizing solution consists of a chemical compound that is mixed with water and applied to a surface.

Once the testing swab has been swiped across the surface of interest, the swab is placed in a solution and undergoes a reaction, producing light. The swab is then placed in a luminometer, which measures the light intensity produced in “relative light units” (RLUs). The light intensity is directly related to the amount of ATP on the surface, and therefore is an indicator of the amount of organic matter remaining on the surface. High remaining organic residual levels may render a sanitizer ineffective.

How often to do ATP testing? That depends on a lot of factors. Depending on the size of an operation, a company might have 50 different sampling sites and test five of them a week.

Microbial Assays. ATP test results, however, do not correlate to microbial count. The high RLU might result from food residue, not from potentially harmful bacteria. For that reason, ATP testing is complemented by conducting microbial testing on the surface and in the air and/or in the water rinsed through equipment, both before and after sanitizing. Microbial testing can determine what microorganisms are contaminating the production area, which can help identify the source.

These microbial assays generally include testing for aerobic plate count, or APC, which indicates bacterial populations that grow and proliferate in the presence of oxygen (aerobic conditions) and in some instances, may involve more sophisticated testing for genus of bacteria which include potential pathogens such as Listeria spp. Salmonella spp., and/or E.coli spp. These microbial test methods utilize sterile agar plates, swab techniques, or petrifilm to verify the effectiveness of the sanitizing practices utilized in the food processing facility.

For a small operator, the prospect of utilizing microbial assays to verify the success of a sanitation program might seem intimidating and expensive, but do not hesitate to seek outside help. Once again, there are a number of chemical suppliers and related companies that provide service and assistance in establishing verification and validation programs, including testing and monitoring. Associations also have technical bulletins. The cost of a foodborne illness outbreak would undoubtedly cost more than hiring an outside lab. Again, there is a great deal of variation in how often a company carries out microbial assays to verify the efficacy of its sanitation program.

Remember, the new FSMA may mandate written hazard-control plans, and state departments may extend FSMA requirements even to smaller operators that FSMA exempts. Once a hazard-control plan is in place, you must have verification that it is working effectively. Utilization of visual, chemical, and microbial test methods enforce and ensure that proper sanitary practices are being carried out. The final key piece to any sanitation puzzle, of course, is employee training and implementation of proper sanitary procedures. Practicing all the measures in your plan on a continuous basis will validate the sanitation plan’s efficiency and effectiveness in food processing facility.


Dr. Keener is a professor in the Department of Food Science at Purdue University and is a core faculty member with the VFSTC. This article was written with the assistance of Jacqueline Kochak, who is with the Auburn University Food Systems Institute, home of the VFSTC. Dr. Keener can be reached at kkeener@purdue.edu.

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