Microbial contamination not only relates to the presence of pathogens but also to spoilage organisms, such as Pseudomonas or lactic acid bacteria. Early spoilage and product quality are increasingly becoming a blemish on a brand’s reputation. Brand reputation, financial impact, and citations by regulatory agencies are at the core of the problems that occur when cleaning and sanitation is not effective in a food processing or manufacturing facility.
Through proper cleaning and sanitation, many biological risks can be prevented and controlled. In order to confidently state that a cleaning and sanitation operation was conducted successfully, the process should be verified on a regular basis. Choosing appropriate methods and relevant test points, determining an adequate sampling frequency, and analyzing the data collected over time, are all critical elements of a sound sampling, testing, and monitoring plan. Reliable data is derived from quality instruments or test kits that are routinely calibrated and tested for accuracy, and to eliminate human variability, individuals collecting the samples must be properly trained. For as long as these concepts have been known in the industry, many methodologies have emerged in the test kit market for verification of cleaning and sanitation as a part of an environmental monitoring program. Each method brings value to an environmental monitoring program, but choosing the right tools is key.
Visual inspection is a longstanding method and allows for a big picture assessment of the equipment and surfaces. It simply means visually evaluating a piece of equipment or plant floor location with a flashlight or blacklight. This can be useful to find the buildup of foodstuffs that were missed during cleaning as well as discovering damaged equipment. Documentation of a visual inspection can be beneficial when assessing other data and determining trends in sanitation. For example, if the wear on a piece of equipment or part is progressing over time, maintenance can be done before a serious problem occurs. Although it has benefits, visual inspection has several limitations. It is a subjective and imprecise means of verifying proper cleaning. More importantly, even if a surface appears immaculate with no apparent residue, this does not mean it is. Visual inspection cannot ensure that all of the food residue from the previous run has been cleaned away or that a sanitizer effectively reduced the microbial level on the surface.
Another enduring tool in an environmental monitoring plan to verify cleaning and sanitation is microbial detection through direct enumeration by a microbiological medium. This includes not only pathogens but indicator organisms as well. Currently in the industry there is great focus and importance placed on pathogen detection, however, screening for indicator organisms is also important. Understanding the trends and harborage areas of spoilage organisms to help target cleaning and sanitation efforts can increase product quality and perhaps even lengthen the shelf life of a product. The main limitation of microbial detection through traditional methods is the amount of time it takes to obtain results, especially when compared to other methods.
Before the sample reaches the microbial enumeration medium, it must first be successfully collected and also released from the collection device. Not all materials used as collection devices have the same efficiency in recovery. It is important to choose the best collection device material for all surface types being tested and ensure that the material is biocide-free. According to ”Principles of Microbiological Troubleshooting in the Industrial Food Processing Environment” edited by Jeffrey L. Kornacki, when choosing the proper collection device, the size and shape must be appropriate for the area or surface being tested.
A swab works best in crevices and small areas that may be difficult to clean. However, due to their small size, swabs are not very sensitive when sampling large areas and can easily be impeded in areas with a heavy soil load. Pre-moistened sponges provide greater sensitivity when sampling large, flat surface areas. They also allow for greater pressure to be applied to help pick up microorganisms that have strongly adhered to the surface either by soil or their own matrix of sugar and proteins. Direct contact of a media to a surface is sensitive and works well on flat surfaces, but not as well in small spaces or gaps.
The most common rapid approach used in many facilities to assess sanitary conditions post cleaning and sanitation before starting production is measurement of levels of adenosine tri-phosphate (ATP) on surfaces or in rinse water (e.g., closed systems). Within the last several years, the decreasing size and time to result of ATP systems have made them an indispensable method for verification of cleaning and sanitation. Most ATP systems on the market are simple to use and efficient. They provide an indirect overall estimation of microbial contamination and residual organic matter that may still be present to assess the cleaning and sanitation efforts.
Instruments used for the detection of ATP, or luminometers, establish a correlation between light emitted from a bioluminescent reaction proportional to the amount of ATP present, expressed as Relative Light Units (RLU). Determination of pass/fail thresholds for ATP detection should be based on baseline values representing acceptable clean conditions. If the ATP level for an area or surface is greater than the allowable limit for that location, it can be cleaned and sanitized again before restarting production is allowed. In contrast, if using a microbial culture method, results are not known until at least 24 hours after production has begun. The rapid results offered by an ATP method allow for more immediate corrective action than most methods. As with the previously mentioned methods, it is equally important to understand the limitations and functionality of any ATP detection system being used, including but not limited to, potential food or sanitizer interference.
Choosing a luminometer is not a decision that should be taken lightly, as it will be a critical component in verifying that a facility’s cleaning and sanitation procedures are effective. Firstly, the system needs to be sensitive enough to detect low levels of residue or contamination. The components on the luminometer should be of good quality. In particular, the apparatus that detects the light emitted from the reaction of the ATP, luciferin, and luciferase should be best in class. For example, a photomultiplier detector may be more expensive but is considerably more sensitive than a photodiode. Capable of detecting small amounts of light emitted from the reaction, a photomultiplier is more sensitive given that it multiplies the current produced by the incident light by a million times. Instruments with a photodiode rely on the swab formulation to strengthen the light signal to get a better reading. However, users must be quick to place the swab into the instrument after exposing the swab to the chemistry containing the luciferin and luciferase enzymes. There is a significantly shorter window of opportunity to analyze the swab as the increase in enzymatic activity reduces the amount of time that the light is emitted from the reaction.
Secondly, results should be repeatable and consistent from swab to swab, analyst to analyst and day to day. This is particularly important when monitoring data over time and looking for trends. Having to conduct extra cleaning or missing contamination due to variance from the instrument or swab is not an efficient way to verify cleaning and sanitation. Moreover, many instruments can have differing results due to temperature changes or even the position the instrument was held in during the reading. Choosing an instrument that provides sensitive and consistent results at a wide range of temperatures is essential. This is especially true if part of the environmental monitoring plan includes cold rooms. As a measurement of repeatability, the coefficient of variation expressed as percentage can be calculated for an ATP detection system. The lower the coefficient of variation, the more repeatable results that can be obtained from the method.
A comprehensive but simple-to-use data management system can easily upload or import data from the ATP instrument and can be a beneficial tool to help with test planning and data trending. Documentation is a key element of managing compliance with preventive controls, and having a system that can easily display the data in a way that is useful can improve cleaning and sanitation over time. In a well-established environmental monitoring program, it may not be necessary to sample every test point before every startup. A randomization algorithm is helpful to enable more efficient environmental monitoring without bias from operators. Monitoring trends and data can be accomplished even more effectively if the system allows for recording not only the ATP values but also other criteria such as visual inspection results. This allows for a quick view of a more complete picture rather than just one component.
It is beneficial to note that ATP detection systems detect one thing—ATP. Determination of whether ATP detected on a surface has come from the food or microorganisms or a combination of both cannot be deciphered by a luminometer. If it is a combination of both microorganism and food, it is impossible to know what proportion of the ATP being detected comes from the food or microorganism. Additionally, there is no correlation between RLU values and the number of microorganisms present on a surface. There is considerable variation in cellular ATP levels, particularly between species of microorganisms.
Visual inspection, microbial enumeration, and ATP detection all have a role to play when verifying cleaning and sanitation. Visual inspection allows for the quick, simple detection of heavily soiled surfaces. Microbial detection can help determine the source of product contamination, identify niches harboring specific classes of microbes missed during cleaning and sanitation, and track where microorganisms may be going next. ATP bioluminescence systems provide a rapid, actionable result if cleaning and sanitation did not successfully remove foodstuffs or microbes. The key to link all of these tools together is to analyze the data and monitor for trends to gain a true understanding of the large picture in regards to microbial control in a facility.
Lingle is senior microbiologist for global technical service at 3M Food Safety. Reach her at firstname.lastname@example.org.