5 Fundamentals of Allergen Analysis #2: Risk-Based Sampling

An important and often overseen part of allergen analysis is the process of sampling. Allergens that make their way into a product by cross-contact can be considered contaminants. Yet unlike other “contaminants”, the distribution of the allergen contamination tends to be heterogeneous, a result of most cross-contact processes. Furthermore, allergens do not spread once they are in the product (as would be the case of microbial contaminants). The sampling strategy is therefore of great significance in allergen control.

Define the type, number and size of samples to take

Some of the most advantageous sampling strategies are those based on previous risk-assessment. The best way to begin is to define the possible allergens, their presentation and allergen load, as well as the frequency and the points where cross-contamination is more likely to happen (and how). It also helps to define the kind (e.g. swabs, rinsates, extrudates, finished product, etc.), number and size of samples to take, as this allows for an initial, rough estimate of the amount of contaminant allergen to be expected. Thus, if the only possible cross-contact point in a product is the storage room, fewer samples will have to be obtained than if the production line itself is a critical point. Similarly, powder-based allergens or allergen-containing materials can be spread through the air, necessitating the swabbing of surfaces other than only immediately adjacent ones.

Avoid composite samples!

The nature of the sample itself and the process from which it derives also have an impact on the size of the sample to be taken. This also affects the degree of homogeneity that can be achieved when processing it. Most methods are able to test a minimum amount of sample (normally between 0.2 to 1 g and, in some cases, up to 5 g). Therefore, these small amounts must derive from a thoroughly homogenized sample that is as representative as possible of the material being tested. This is of particular importance when this material is in itself heterogeneous (like most finished products). 

But beware! By no means does this mean that equivalent materials should be pooled to obtain a larger and more representative composite sample before homogenization. In fact, the opposite is true. Precisely because of the uneven distribution of allergens, the composition of samples tends to dilute the allergens, rendering them undetectable by regular methods of analysis. Furthermore, the pooling of samples leads to the loss of vital information regarding the exact time and origin of the cross-contact. These are just some of the challenges that can come up during allergen analysis. In the next installment, we address how to prepare the material for testing.