Cleaning Validation and the Role of Sampling in Your Production Environment

Microbial cleaning validations should always include indicator organisms and important pathogens, such as Salmonella or Listeria spp.

Why conduct a cleaning validation?

Keeping the food process environment clean is key to avoiding cross-contamination. National and international regulations require the food industry to ensure that foodstuffs placed on the market are safe for consumption and are under specifically defined thresholds for (if not free from) chemical, physical, biological and allergenic traces. In the European Union, for example, EC/178/2002 states that products may not be injurious to health or unfit for human consumption.

Cleaning validation plays a crucial role in quality control by demonstrating that a documented cleaning plan works as it is intended to work. Validations should be carried out on a regular basis and include, if necessary, a documented corrective action. Products, equipment, personnel, protective clothing and other items in the production process are subject to cleaning validation, though it is important to keep in mind that the validation should be based on the associated level of risk. Everything that could be a potential source of cross-contamination should be taken into consideration.

How do you know if it’s clean?

The first step for a proper cleaning validation is to determine how clean is clean enough. In other words, what are the acceptance criteria? These can be measured in cfu/ml (colony forming units per milliliter) or cfu/cm² for microorganisms and µg/cm² for chemicals or allergens. ATP test systems can also be used to check the surface for residues, but this will not work in all environments: for meat or fresh fruit production, ATP levels will be much higher than in a bakery. There is a simple reason for this: after a living cell is destroyed, the ATP degrades. For ATP tests, pass and fail limits of cleanliness should be determined by the facility and documented as to how they were determined.

Microbial cleaning validations should always include indicator organisms and important pathogens. For ready-to-eat products, for example, these may be Salmonella or Listeria spp., the acceptable limit of which is always at zero. Though there are several different methods on the market to monitor for pathogens, the gold standard is culturing, which relies on multiple enrichments and petri dishes. These, in turn, rely on a proper environmental sampling method.

How do you take samples in your process environment?

Generally, there are four ways to take samples from the process environment: swabs, sponges, direct methods (contact plates, dip-slides), and rinse water. Swabs are suited for gaps and corners while sponges are better suited to test larger surfaces. The use of a direct method such as a contact plate or a dip-slide does speed up the sampling procedure and reduce the requirements for other consumables (pipettes, petri dishes, dilution buffer etc.), but it drastically limits the sampling area (approx. 10-25 cm²). Testing rinse water has two advantages: there is no need for a special sampling device and it more accurately represents the sampling area. However, what is gained in scope is lost in precision, as with rinse water the exact location of the contamination cannot be determined.

A cleaning validation is most effective when tailored to a specific production environment. A variety of sampling and test methods may be required to cover all potential sources of contamination.