Food Allergen Testing - Facts vs. Fiction (1)

As food allergens represent an ever-present risk for individuals with allergies, it is crucial for food producers to conduct routine tests for potential allergen contamination in their products. This sounds simpler than it often is.

Food products can range widely from straight raw materials, such as cereals, to highly processed ready-to-eat products. Therefore, the composition of food products varies according to the amount of protein, fat, salt and other compounds present. Test methods are expected to analyze all food sample types for allergens with equally reliable results. This however is often far from achievable in reality.

In this series, we will shed some light on common misconceptions in allergen testing.

A test kit from the shelf works with any food matrix

Taking a test kit from the shelf and starting to test right away does sound tempting and would be the quickest way to get to results. However, are these results reliable? In reality, food products are highly diverse and certain test methods may work better for certain food samples. The extent of processing adds further complexity to this equation. The best testing method must be determined in a food matrix validation study. Here we explain some prior considerations and how to perform these studies on-site.

Handling new food types

When we receive or encounter a new food type that has not been tested before, we undertake a spike recovery validation to ensure it works as expected with our test kits. We will spike three different levels of allergen in to the sample – low, medium and high – to cover the detection range of the assay.

The low allergen spike will either be close to the Lower Limit of Quantitation (LLOQ) of a quantitative test kit such as ELISA (in this case the lowest value calibrator above 0 ppm), or close to the Limit of Detection (LOD) of a qualitative lateral flow device (LFD). The medium spike will be in the middle of the ELISA calibration curve, and the high spike will be at or near the Upper Limit of Quantitation (ULOQ) (the highest ppm value calibrator).

What can influence my spike?

If we spike for example almond into chocolate, we would expect to see a recovery of 40% or less which could be boosted to 60% or above when using extraction additives. From experience, chocolate is one of the most challenging food matrices to test – it is full of tannins and other polyphenols which can bind to any allergenic protein that may be present and form insoluble complexes which are difficult to extract.

Improving the extraction of your spike

Such difficulties can be overcome by adding extra protein to the extraction buffer. The excess protein binds to the polyphenols and makes the allergens available for extraction. One protein of choice is fish gelatin. Other proteins such as milk powder can be used to improve the extraction efficiency from high polyphenol containing foods. If you are using milk powder, be careful not to contaminate your laboratory space, especially if you are carrying out milk allergen testing.

The result…

During implementation of an allergen control plan, it is highly recommended that the selected allergen test method is fully validated on the food producer’s specific food matrices. By following the described validation rules, a reliable and accurate result is guaranteed for almost every food product.

In our next issue of “Food Allergen Testing – Facts vs. Fiction” we will give insight to the common misconception that “May contain…” statements can solve all our problems.


This article was originally published in "International Food & Meat Topics", Volume 28 Number 1 (2017)