When it comes time to begin the process of defining individual test sites in an ATP sanitation verification program, the question often becomes, “how do I choose the best sites for testing?” The key to answering this question is to focus on a set of test sites that provide a representative sample of the sanitation that was performed during each cleaning event.
Once the full population of representative sites has been determined, the next question becomes, “how do we choose the correct number of sites to sample after each cleaning event?” To address these questions, we’ll start with an exploration of what constitutes a representative sample.
In a food production environment, ingredients flow along a series of physical surfaces on their way to the final package or consumer. Each unique surface the ingredients come into contact with should be considered a potential test site. In most cases, any spot on the surface that is typical of the entire surface can be selected as the sampling site.
In the case of a conveyor belt, for example, even if it’s 100 feet long, a spot selected at the beginning, middle or end could be considered representative of the cleanliness at any spot on the conveyor’s surface. But, the larger the surface, the more necessary it becomes to validate that assumption and rotate sampling sites along the surface.
It is not always necessary to select each individual surface for testing. Consideration must also be given to the type of cleaning that was performed on these surfaces. In many ways, the consistency of the cleaning process can dictate the number of test sites — with fewer being necessary the more standard the process. In the case of utensils, trays or bins, for example, which were cleaned and sanitized in a large automated dishwasher, sampling one or a few of the items from the dishwasher should give a representative sampling of the cleaning efficacy for all items in this cleaning cycle.
Establishing good representative sampling requires some assumptions. The key is to make these assumptions with as much data as possible. When first getting started, the assumptions might be based on expert opinions or past experience, and it’s always best practice to extend the net wider where uncertainty exists. But as experience builds with existing equipment and processes, the choice of test sites and concept of representative sampling should be reviewed regularly to test the validity of the assumptions. This process can become a type of validation cycle and new assumptions can be tested as they occur.
Once the pool of potential test sites has been established, the process moves to establishing a quantity of test sites that will reflect a representative sampling of each cleaning event. Most facilities utilize a random selection of a subset of test sites for this process. The quantity established is usually a function of experience, statistical probability, comfort level and budget, with the latter item often becoming the determining factor.
In the real world, we all must function within budgets and other fiscal restraints that often heavily influence our programs. But best practices call for a balance of budget, comfort and probability to achieve an effective representative sampling. The optimal ATP sanitation verification program is one that provides management with the assurance they need by showing that the cleaning and sanitation performed was effective at removing or rendering inert the contaminants on surfaces that can make our products unsafe or unsuitable for consumption.
Neogen offers the industry leading AccuPoint Advanced ATP Sanitation Verification System, the only AOAC-approved ATP sanitation system, which provides the most accurate and consistent results as proven by an industry-leading source. Visit our environmental monitoring webpage for more information dedicated to helping facilities establish robust environmental monitoring programs.