Use the right technique. Swabbing of hard-to-clean spots on the processing lines (nooks and crannies) is important. Multiple swabs should be taken, especially in the initial stages of cleaning validation on a processing line to identify the spots that are hardest to clean. Those spots can then become the focus of subsequent cleaning validations and verifications. Allergen cleaning protocol effectiveness should be re-validated periodically or whenever anything changes (product formulation, equipment matrix, processing conditions, etc.). The frequency of re-validation is not fixed and is dependent upon the frequency of changeovers. When using the recommended environmental swabs, the swabbing technique can vary without much effect on the observations. Swabs and surfaces can be either wet or dry.
Interpret the results. LFDs offer qualitative results. Thus, results should be interpreted primarily as negative or positive. The goal for cleaning validation should be “negative by swab” after documenting that the chosen LFD is fit for purpose.
Commercial LFDs provide sensitivity limits in concentration terms, such as ppm, and relate to the allergen concentration in the swab extraction solution. This term has no bearing on the allergen concentration that might be found on a finished product that comes in contact with the equipment surface. Swab test results should instead be provided in terms of µg/cm2, but that presumes users will swab uniform areas of the equipment surface. Since irregular surface areas are swabbed, the most appropriate expression of results would be µg/swab. And since the degree of hazard to the finished product cannot be determined from a swab result, the goal should be “negative by swab” as noted above unless you are brave enough to test finished product (see below).
Know when to test finished product. The results of equipment surface swabs cannot easily be translated to finished food products. Swabs with LFDs offer qualitative results while finished product testing is usually quantitative. LFDs tend to be extremely sensitive; they can detect extremely small amounts of allergen on equipment surfaces. When the subsequent product is manufactured on the shared equipment, allergen residues will likely be transferred to that product especially on the initial amount of product made after changeover. However, depending upon the amount of residue remaining of the equipment surface and the volume of the next product that passes over that equipment surface, the residues may not always be detectable in that next product. The testing of finished product is the only way to determine if detectable residues are present.
For obvious reasons, food companies are reluctant to test finished food products for undeclared allergens because the presence of such residues means that the product cannot be sold. However, the ultimate validation of an allergen cleaning procedure involves ensuring that no detectable residues are present in the finished product. If a robust swabbing strategy has been used and no allergen residues have been detected by swab with LFD, then it is very unlikely that allergen residues will be detected in the finished product. In those circumstances, testing of the finished product does serve as the ultimate validation.
Dr. Taylor is the co-founder and co-director of the Food Allergy Research and Resource Program (FARRP) at the University of Nebraska, Lincoln. Reach him at email@example.com. Dr. Baumert is the co-director at FARRP. Reach him at firstname.lastname@example.org.