Chemical sanitizers are designed to address specific microorganisms in food, beverage, dairy and pharmaceutical processing hygiene. However, in most facilities, the microflora of a processing line may shift due to changing production conditions. In these cases, sanitizer rotation is a worthwhile action to address the spectrum of microbial activity as well as concerns about the development of microbial resistance.
What is Microbial Resistance?
Microbial resistance is broadly defined as the ability of the microbe to survive and propagate under conditions that were previously lethal. Some of these conditions include temperatures, pH, water availability, and chemical exposure. There are two accepted types of microbial resistance: intrinsic and acquired.
What is the difference between intrinsic resistance and acquired resistance?
Intrinsic resistance is the microbe’s natural ability to survive certain types of chemicals. For example, Iodophores are effective against various Gram positive and Gram negative bacteria but are less effective against spores or bacteriophage.
Acquired resistance is when organism strains have survived sub-lethal exposure to chemicals. Sub-lethal exposure can be low concentrations of acids or low parts per million (ppm) of chemicals. Acquired resistance can be further classified. Some of those definitions are listed below:
- Acid Tolerance: tolerance to acidic conditions.
- Chemical Tolerance: tolerance to chemical exposure.
- Cryo Tolerance: tolerance to freezer, or sub-zero conditions.
- Thermo Tolerance: tolerance to thermal conditions.
Why use chemical sanitizers in processing plants?
There are two goals for plant sanitizing. The first is to maintain control of the plant sanitizing program and the second is to prevent any existing microbial situation from becoming worse.
A processing plant can maintain control of its sanitizing program by identifying areas of concern and maintaining them on a master Standard Sanitation Operating Procedure (SSOP) schedule. This includes the identification of problem areas (biofilm formations, bioaerosols, etc.) and the routine monitoring of these areas by microbiological means (either by adenosine triphosphate (ATP), daily plating, or monthly baseline numbers).
Preventing existing situations from worsening can be accomplished easily by putting the plant on a sanitizer rotation program. It is recommended that plants alternate sanitizers during the week to prevent bioresistance or proliferation of specific flora1.
Why rotate sanitizers?
The reason for sanitizer rotation is that using only one type of sanitizer may eliminate one type of organism, but allows others to proliferate instead. For example, a plant uses a sanitizer that is highly effective against Gram-positive bacteria. However, the sanitizer actually allows Gram-negative bacteria to flourish because there are no Gram-positive bacteria to compete for resources. The site can combat this issue by using a different type of sanitizer once a week that is more efficacious against Gram-negative bacteria thus leveling the microbial field.
Does switching sanitizers to something like chlorine cause additional corrosion problems?
Sanitizers are highly effective and relatively low in corrosion when used at the appropriate dilution. Please refer to the label for correct dosage rate, metal interactions if listed, and contact times for sanitizing.
What precautions do you need to take when rotating sanitizers?
It is important to note that sanitizers may not be compatible with each other. For example, do not follow the use of an acid cleaner or sanitizer with a chlorinated sanitizer without rinsing well between chemical applications. Nor should you follow a quat with chlorine without rinsing well. Both of these situations can produce a dangerous chemical reaction where toxic gases can be produced. It is best to thoroughly read all Safety Data Sheets (SDS) and technical data sheets prior to application.
Most sanitizers are ineffective against large amounts of organic debris. Residual organic debris will effectively cancel the germicidal ability to sanitize2. To enhance the effectiveness of a sanitizer, thorough cleaning of the equipment, or area to be sanitized, is necessary.
Remember: a dirty surface cannot be sanitized. It is important to thoroughly clean equipment before sanitizing.
Note that when a sanitizer is rendered sub-lethal, microorganisms may become resistant.
It is also possible to employ a technique known as double sanitizing. In double sanitizing, the surface is exposed to a very strong solution, thoroughly rinsed with potable water and then sanitized. In this case, the initial sanitizer application oxidizes away any interference.
Another issue to be aware of is the fact that employees may not follow the master sanitation schedule. Employees may routinely forget to rotate sanitizers. The sanitation schedule must be clearly posted for all employees to follow. While these are just a few of the issues that can occur when rotating sanitizers, overall, sanitizer rotation is more beneficial than harmful. By incorporating a sanitizer rotation schedule into a master Sanitation Standard Operating Procedure, processors can both maintain biological control of their environment and prevent any existing microbial situations from worsening.
Diversey's hygiene specialists can help design bespoke sanitizer rotation programs aligned to the specific requirements of individual production plants. Contact us for a consultation.
1Gregersen, J., “Clean Sweep Sanitizers and Disinfectants are Only as Good the SSOP’s that Govern Them”, Meat Mark. Technology, 53-58, 2005.
2Yousef, A. and Juneja, V., Microbial Stress Adaptation and Food Safety, CRC Press, 2003.