When choosing a target for the validation study, it is best to choose something that is present at high levels, has a high protein content and is hard to clean away from the line. You are trying to demonstrate that the clean works in the most challenging situations, so ideally you want to be using your worst-case scenario to prove this. It can be tempting to opt for a target that can be easily cleaned away to establish a quick win - however by basing the validation on the worst-case situation, it should then be possible to gain assurance that the cleaning will work across multiple scenarios where the cleaning is less challenging. It would not be possible to make this assumption based on validation of a clean of something easily removed or present at low levels.

Step 4: Choosing the right allergen testing strategy

You need to be sure there is a good laboratory test method to detect the chosen allergen in your samples - ideally you should use a quantitative method. For allergen cleaning validations, the recommendation is to use an ELISA test where possible as these look for protein and will provide quantitative results (within a range). As it is the protein that causes people to have allergic reactions, it is good practice to be aiming to detect this with any testing. PCR testing is generally not recommended for allergen cleaning validation studies as these tests are looking for DNA rather than protein, and the results are not easily quantifiable or translatable into levels of protein. You may be in a situation where there is no suitable ELISA test for your target allergen (as is currently the case with celery). In these situations, the advice is to consult with the lab and see whether there is another target you could use, or whether the PCR test will give you the information you need.  

Bear in mind that some validation work may need to be done by the lab if they haven’t tested your products or source of allergen before - they should be able to advise you if this is needed. This might include spike recovery testing of your next off-line product, as well as cross-reactivity checks. Spike recovery testing is used to check whether the lab’s test can detect the allergen in a product or ingredient, should it be present as carry-over. Testing a positive control is also a key part of validating the test method, as is outlined below.

Step 5: Collecting your samples for laboratory testing

The samples you should be looking to take for your study include:

• Positive control - this is the source of the allergen contamination of your line/equipment. It could be an ingredient, part-made product or finished product depending on the equipment being cleaned. Your positive control should be tested once to ensure the allergen can be detected and at the level you are expecting it to be at – you do not need to test this for every round of the validation. 

• Post-clean samples – typically these will be swabs, rinse waters or purge material. The type of sample will be dependent on the cleaning method being performed. When deciding where to collect the post-clean samples from, focus on the areas that are most challenging to clean, as these represent the worst-case scenario. If these can be cleaned well, then the less difficult to clean surfaces also will be. If testing rinse waters, ensure it is the final rinse that is collected, as this will most closely represent what the next product will be exposed to.  

• Next off-line product – this typically is the first ingredient or product that comes into contact with the equipment after the cleaning has been done. Testing this product or ingredient is the only direct measure of what the consumer will be exposed to. If carry-over of allergen is detected in this sample, this represents a risk to an allergic consumer.

Industry best practice is to repeat the validation exercise three times (but only test the positive control once), and to achieve non-detectable results for all post-clean and next off-line samples in three consecutive rounds. Where possible, include different shifts to demonstrate that the clean is performed consistently and is fit for purpose regardless of who does it.  

Step 6: Results and next steps

Part of the planning stage of the validation study should include consideration of what action to take should unexpected results be obtained. Where any results come back as detected, this should deem that round of validation failed, and the whole exercise should be repeated. Before this, it is essential to review where the result came from and to try to understand what could have caused it on that occasion. There could be a simple fix that would save potentially repeating the exercise unsuccessfully.

A successful cleaning validation  study is one that is well planned and considers all the aspects outlined above. Always keep in the front of your mind that you are collecting evidence of effectiveness and consistency of the cleaning procedure based on your worst-case scenario.