Toasters, Pasta and Cupcakes - Cross Contamination

A recent study looked at how much gluten contamination occurs in various food prep methods — and the results were surprising.

A recent study published by researchers from the Celiac Disease Program at the Children’s National Health System and the Harvard Celiac Disease Program looked to see how much gluten cross-contamination would occur with three different types of food preparation methods: cooking pasta, toasting bread and slicing cupcakes.

Cooking Pasta

To test gluten transfer when cooking gluten-free pasta, the researchers used the same pot after cooking gluten-containing pasta first. When reusing water contaminated with gluten to cook gluten-free pasta, all 12 samples had gluten detected greater than > 20 ppm. When the contaminated cooked pasta was rinsed under cold water, five out of six samples had detected gluten, but less than < 10 ppm. If the shared pots were rinsed with water alone first, or scrubbed with soap and water before cooking the gluten-free pasta, there was no gluten detectable. Thus, either cleaning method works to prevent gluten transfer. 

Slicing Cupcakes

Slicing cupcakes: Re- searchers sliced a gluten-free cupcake using a knife that had just prior sliced a frosted gluten-containing cupcake. Just under half (46%) of the samples had detectable gluten at 10-20 ppm and 7% even > 20 ppm. However, if the knife was washed either with soap and water, rinsed in running water, or cleaned with antibacterial hand wipe, 93% of the samples were found to be uncontaminated. All three methods of cleaning the knife were equally effective.

Toasting Bread

Toasting bread: Gluten transfer was tested when toasting gluten-free bread in a shared toaster with gluten-containing bread (rolling and pop-up) and visible crumbs present. Toasting in a rolling toaster detected gluten in 20% of samples at 5-10 ppm, while toasting in a shared pop-up toaster was not associated with any detectable gluten in the 20 samples tested. 

The Takeaway

Certainly, the results of this study are intriguing. With this published data, there is evidence to show what those with celiac have long believed: that sharing water to cook gluten-free pasta is a significant source of contamination. Hopefully this study should provide more support to those advocating for safer food preparation practices in restaurants.

But should the toaster results change the way you prepare food? Should those with celiac feel safe using a non-dedicated toaster? Not quite. More studies with larger sample sizes are required to confirm the results, since only 20 samples were tested for each toaster. Given the severity of symptoms some patients may develop after being contaminated with gluten, keeping a dedicated gluten-free toaster seems like a simple measure to avoid feeling quite unwell post gluten contamination.

Finally, this study confirms that simple cleaning measures for cooking utensils with soap and water is very effective to eliminate gluten contamination, and possibly that separate utensils and pots for GF cooking are not necessary.

Study review by Dr. Dominica Gidrewicz, Gastroenterologist, CCA Professional Advisory Council


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