Mastering Allergen Testing: Webinar Q&A with Barbara Hirst

Webinar Q&A: Keynote Speaker Barbara Hirst Answers Questions on Allergen Testing

Following our industry webinar, Mastering Allergen Testing: Best Practice and the Role of Rapid Testing, keynote speaker Barbara Hirst joined Klipspringer’s Engagement Manager, Guy Bush, to answer the audience questions we didn’t have time to cover during the live session.

The following article also includes Barbara’s responses from the webinar Q&A, bringing together all of her expert insights for easy reference.

If you have any further questions about allergen testing, Klipspringer’s in-house Technical Team is here to help. Simply click here to submit your query, and we’ll be in touch.

WEBINAR: Watch the complete webinar online

Barbara Hirst | RSSL

Barbara is a Senior Consultant in the Food Safety and Quality team at RSSL, specialising in allergen management. She works closely with food production sites to identify allergen control challenges and implement practical and effective solutions.

Do denatured proteins still present an allergen risk?

Barbara addressed this question during both the live webinar and the following Q&A.

Barbara explained that although denatured proteins can be more difficult to detect, this does not mean they are no longer allergenic. Put simply, they can still pose a risk to allergic consumers.

Barbara added that the Morinaga test kits discussed during the webinar are particularly well regarded for their ability to detect denatured proteins and are becoming more widely used across the industry. At RSSL, Morinaga tests are used for a range of allergens, including milk and egg, where they perform especially well.

Barbara also highlighted the importance of positive control testing. This involves submitting a product known to contain the target allergen for ELISA testing. The results can help to determine whether the selected on-site test method is suitable for the specific product and processing conditions being evaluated.

Why are qualitative results recommended for verification purposes rather than quantitative testing?

Barbara highlighted that validation and verification serve different purposes and therefore require different testing approaches.

Validation

Validation is not only about determining whether an allergen is present, but also about understanding how much is present. For this reason, it requires a quantitative test (e.g ELISA) which provides a numerical result rather than a simple detected/not detected answer.

Verification

Verification follows validation and is focused on confirming that existing controls and processes are still working effectively. For this purpose, a qualitative test that provides a detected/not detected result is sufficient, provided the limit of detection is understood.

Regarding the limit of detection (LOD), Barbara explained that this is the lowest concentration at which an allergen can be reliably detected.

Quantitative tests, such as ELISA methods, also have a limit of quantification (LOQ), which is the lowest concentration at which the allergen can be accurately quantified.

How can sites balance practical on-site requirements such as speed and ease of use with the need for accuracy?

Barbara acknowledged the pressures sites face around cost and speed but warned that there are no shortcuts when it comes to allergen validation. She explained that if factories attempt to take the “cheap and cheerful” route, their results may not be reliable and could create a false economy.

Barbara stressed the importance of careful planning, taking samples from the correct locations, using appropriate test methods, and working with competent laboratories to ensure confidence in the results being generated.

How often should allergen testing programmes be reviewed or revalidated?

Barbara advised that allergen validation should always be reviewed whenever anything significant changes. Examples discussed included changing cleaning chemical suppliers, modifying equipment, altering production layouts or changing the cleaning process itself.

Alongside change-driven reviews, Barbara recommended carrying out at least an annual formal review to confirm whether anything has changed that could impact the effectiveness of allergen controls. She also noted that some retail customers may require annual validation activities as part of their own supplier policies.

Why do rapid swabs still require site-level validation if the manufacturer has already validated them?

Barbara explained that while the manufacturers of rapid tests carry out extensive validation work before launching their products, they cannot possibly validate every individual food matrix or production scenario.

Using the example discussed during the webinar, she explained that a milk test may have been extensively validated on liquid milk, cream or even cheese, but not on a specific product such as a Parmesan-topped ready meal.

Without site-specific validation, sites cannot assume the test will perform with the same sensitivity in every application. In some cases, Barbara noted that sensitivity can be reduced by 100- or even 1,000-fold depending on the ingredient or product matrix involved.

Why is rapid testing described as a qualitative method?

Barbara clarified that rapid tests remain qualitative because they provide a yes-or-no answer regarding allergen presence. Although rapid tests may have a defined limit of detection, they do not measure how much allergen is present.

Quantitative ELISA testing, by contrast, is used when sites need to understand allergen concentration levels, such as during cleaning validation studies or finished product analysis.

How can sites reduce false positives in rapid testing programmes?

Barbara returned to the importance of validating rapid tests before use. Validating them against site-specific products and processes helps to reduce the risk of both false positives and false negatives.

She explained that false positives can lead sites to believe equipment is not clean when it actually is, potentially resulting in unnecessary recleaning or production delays.

However, false negatives present a greater risk, as sites may believe allergens are absent when residues are still present. This could result in subsequent products being manufactured under the assumption that equipment is clean, when allergen residues remain on the line.

Is a laboratory ELISA method always more sensitive than a rapid test, and is it possible to get different results for the same sample?

Barbara stressed that it is not possible to make a generalised comparison, as there is a wide range of tests on the market that detect slightly different things and operate with varying levels of sensitivity.

She also confirmed that different ELISA and rapid testing methods can absolutely produce different results for the same sample.

However, variations in results do not automatically mean that one method is correct and another is incorrect. Instead, they may arise because different kits target different proteins, use different analytical approaches, or operate at different sensitivity thresholds.

The key, once again, is understanding how each method performs through proper validation work.

Is there a recognised reference list of cross-contaminants that sites can use?

Barbara explained that all biological assays, including both ELISA and rapid tests, are likely to demonstrate some degree of cross-reactivity, which can lead to false positive results.

Manufacturers of allergen testing kits will usually provide cross-reactivity reports and validation data outlining known interactions. Barbara stressed that food factories are responsible for reviewing and understanding this information before implementing a testing method.

However, she also noted that test kit manufacturers cannot possibly assess every ingredient or finished product combination. For this reason, sites still need to confirm whether their own ingredients, products, or manufacturing conditions could create unexpected cross-reactivity issues during testing.

Is it good practice to continue annual swabbing/testing even if it is only to justify the ongoing use of Precautionary Allergen Labelling (PAL)?

Barbara explained that cleaning validation is about demonstrating whether a site’s cleaning process is effective. If residues are found on surfaces, and more importantly if they are carried over into the next product, this is a clear indication that the cleaning process is not effective.

In such cases, the first step is to understand why the cleaning is not effective and identify what can be improved. Businesses have an obligation to achieve the cleanest possible outcome while remaining reasonably practical and cost-effective.

If, despite best efforts, residues cannot be reduced to non-detectable levels when tested using a ELISA method, then precautionary allergen labelling (PAL) may be appropriate. However, there is an expectation that everything reasonable is done to minimise or avoid the need for this.

What is your recommendation for the surface area for swabbing? What about conveyors that are several metres in length?

Barbara confirmed that, ideally, a 10 cm × 10 cm area is what you should aim for when it comes to surface swabbing.

She explained that, prior to sampling, it is best practice to examine the line when it is dirty and identify where product tends to get stuck. These are the areas that should be targeted after cleaning. For long conveyors, this may include worn edges or the space around the rollers.

The key is to maximise the probability of detecting any residual contamination by targeting the “worst-case” scenario. If these areas are clean, it can reasonably be assumed that the rest of the surface is also clean.

Barbara also cautioned against swabbing areas significantly larger than the 10 cm × 10 cm guideline, as this may produce results that are not representative of cleaning effectiveness. While it may increase the likelihood of detecting residue, it does not reflect a defined sampling area.

She added that the swabbing process can be more complex for irregular surfaces such as pipes, which is why results should be reported as amount per swab rather than parts per million, since the sampled area is not always precisely defined.

How are spike recovery tests done and who should do them?

Test manufacturers such as Morinaga will have completed extensive spike and recovery testing, with details typically provided in the validation report. However, it is not reasonable to expect manufacturers to have carried out this process using every factory’s specific product matrix. For this reason, spike and recovery testing should be performed by your laboratory.

Missing this step can lead to false positive or false negative results. The former may trigger an unnecessary product recall, while the latter could result in a serious food safety incident. Despite its importance, spike and recovery testing is not a UKAS requirement and may therefore need to be specifically requested from your laboratory. If the laboratory has not requested an ingredient list, this may indicate that spike and recovery testing has not yet been considered.

Barbara explained that ideally, whenever a laboratory receives a new sample, it should review the ingredient list and consider whether it has analysed a similar matrix before. If it has, repeat spike and recovery testing may not be necessary. If it has not, the laboratory should spike the sample with a known amount of allergen, run it through the assay, and measure the recovery. The expectation is close to 100% recovery, within an acceptable level of uncertainty.

When carrying out a validation and swabbing equipment surfaces, can a composite swab be used?

Barbara explained that composite swabs are almost always a bad idea and a false economy. Although they may appear to save time or cost, for example asking your laboratory to combine five swabs into one sample, there are two key issues with this approach.

Firstly, combining swabs can dilute any contaminant to the point where the test may incorrectly indicate that no allergen is present. Secondly, if a combined sample does return a positive result, it is not possible to determine which of the original swab locations was responsible.

That brings us to the end of our webinar Q&A roundup.

We hope you found Barbara’s expert answers helpful and informative. If you would like to learn more about allergen testing and best practice, we recommend watching the webinar in full.