Consider that the technique must be:
- Appropriately sensitive
- Qualitative or quantitative
- Specific for the target substance
- Able to detect the target substance in the specific matrix (some matrices, like chocolate and meat, do not readily liberate proteins and produce false negatives)
- Able to be performed in an appropriate time frame (minutes to days)
- Able to be performed by the person doing the test (simple to requiring an experienced laboratory-based analysis)
- Economical ($ to $$$)
- Validated (independently for its intended use).
Identify required outcome
An understanding of the required outcome will help to choose the correct method of analysis. Some methods provide quick results and may be useful for production scenarios such as to check if a production line has been sufficiently cleaned. However, often tests which can be performed rapidly do not provide quantitative results. Scenarios where quantitative results may be required, such as finished product testing to verify a VITAL risk assessment, may be required to be performed under laboratory conditions and be more time-consuming.
Specificity of test
Care should be taken to choose a test kit which is looking for the correct target. Allergen testing may be highly specific for a particular target and it is important to establish which marker the test is looking for and whether it will be in the product being tested. For example, kits which detect Beta Lactoglobulin are specific to the beta lactoglobulin fraction of milk. If the cross-contact allergen comes from the casein fraction of milk (which does not contain beta lactoglobulin) then a Beta Lactoglobulin kit would provide a false negative result for milk.
Affect of Matrices
Different matrices will affect the validity of allergen testing. Some matrices inconsistently and reluctantly liberate target proteins for identification by test kits. Also, some matrices, such as cleaning or flush solutions, may destroy target proteins and give a negative result which does not accurately reflect the allergen status of the product or flush. Extreme ph levels, high levels of sugars and salts and polyphenol rich foods (e.g. blueberries, blackberries, vegetables including onion, cabbage, and legumes) may all present challenges for analysis and require specialised extraction protocols to provide correct results.
Affect of Processing
The target protein can be adversely affected by processing, with high temperatures and/or hydrolysis possibly altering the structure of the proteins and making it more difficult to detect. Whilst these changes generally reduce the detectability of the allergen, they may in fact enhance allergenicity.
- For example, soy trypsin inhibitor is a target used by some soy allergen test kits. If the product that you are testing contains hydrolysed soy, or has been exposed to hydrolysis, then the presence of soy will not be detected in this kit and could produce a false negative result.
- Cleaning products may hydrolyse allergenic proteins so it is particularly important that this is considered when testing after a clean.
When choosing an external contract laboratory chose one with:
- Expertise in the field of allergen analysis
- NATA or equivalent accreditation for the performance of allergen analysis
- Validated methods
- A verification program for kit performance in the sample type submitted or has evidence that the sample is suitable for analysis
- Participation in appropriate proficiency programs
- Robust quality control processes
- Reports with clear details around the method and the reporting units provided in the results
Whether using an external laboratory or performing in house analysis it is important to choose:
- Methods or kits from a company with an established history and record of performance.
- Methods where the performance has been peer reviewed, published or approved by an international body (eg. AOAC, AFNOR) or has external validation data to support performance.
- Methods which perform well in proficiency programs
- Methods which are appropriately sensitive, specific and robust and able to detect the target allergen
- Methods which are designed to detect the correct form of the allergen (eg. casein or whey or both dependent on which milk component has been used by the facility).
The preferred method to identify and quantify cross contact allergens in a VITAL risk assessment is to sum the cross contact which is identified by the supplier in each raw material with cross contact allergens identified during a physical audit of the production environment. However, there is a significant role for allergen analysis in:
- validation of the VITAL risk assessment;
- verifying ingredient allergen statements and potential raw material cross contact;
- targeted analysis of problem pieces of processing equipment;
- confirming assumptions made during the implementation of VITAL (such as validation of cleaning);
- testing allergen status of the final product to compare with calculated results from VITAL assessment (this may be especially relevant to high risk environments); and,
- monitoring the effect of critical changes.
The concentration of cross contact allergens in a final product may be validated using analytical testing. It should be noted that this is not a mandatory part of this procedure, but that it may be useful in some circumstances.
Consult a skilled analyst to ensure that the correct methodologies are used and to ensure that the units of measure are appropriate to use with the VITAL Action Levels Grid.
Where the concentration of allergens identified by analytical testing is greater than found during the VITAL risk assessment, consider reviewing the risk assessment for other factors. Consideration should be given to the type of analysis, nature and form of the allergen. It is important to consider the nature of food processing as some processes may reduce the amount of detectable allergen. Further to this, where quantitative measure is done by both analytical and physical measures, in order to consider the situation of greater risk, the greater of the two should be taken. Where analytical results are significantly higher than would be expected based on calculation, consideration should be given to other possible contributing factors.
Finished product testing may be used to verify results from cross contact allergens identified in a VITAL risk assessment. When comparing analytical test results with concentrations calculated from the VITAL risk assessment, it is important to ensure that the units of measure are comparable. The VITAL Action Levels Grid uses concentration (parts per million [ppm]) of total protein. Analytical results use a range of units of measure. Check with the analyst as some kits provide conversion factors to assist in standardising units of measure.