Cross contamination is a real and present danger when the packaging of an item states “may contain” or “produced in a factory which also handles”, even though there are no gluten containing ingredients on the label.
The risk is slightly higher with “may contain” and it caught me out twice before I researched the term to find out what was going on. There are several ways cross contamination can occur but the five main considerations are: packaging, people, the raw materials, the manufacturing process and cleaning methods.
Packaging. Incorrect packaging is, apparently, a major cause of allergen related product recalls. This could be due to a change in ingredients or a change in cross contamination risk and good practice is to ensure that packaging is removed from the packing machines at the end of each batch. Multipacks may have inner and outer packaging, each with ingredient listings adding extra complications.
People. People work on more than one product line and there is a risk of cross contamination through clothing, equipment and on hands as they move around a factory. This risk also extendd to a maintenance risk as tools used on one piece of equipment can transfer allergens to another.
The raw materials. This is a big concern. Different materials may be transported in the same trucks so a wheat crop followed by a corn crop presents a potential hazard. This risk is present right the way up the food chain from farm to leaving the factory securely packaged.
Related to this is a recent study which found that just under a third of grains which do not contain gluten. There is a link to the abstract here. This type of cross contamination is particularly problematic because products labeled gluten free command a higher price but, if the product is naturally gluten free, labelling it as such is disengenuious. It sounds to me like another reason to avoid grains.
The manufacturing process. Here contamination can arise from shared equipment with other lines, storage of ingredients and reworking of old lines into new ones. Reworking happens when enough of one line has been packaged but there is still some left over. Instead of throwing this out it gets reworked into a new product.
Cleaning methods. This can be an issue with hard to clean equipment on shared lines and where the process of cleaning – a high pressure wash for example- which may cause contamination on neighbouring lines.
When I first realised that I had to avoid gluten and dairy I was cavalier about “may contain” and “made in a factory where” but after a few mishaps and doing the research…. More often than not there may be no contamination but there is a real risk that there is and if these foods make you ill, the risk may not be worth taking.