Study on Shared Fryers

As someone with a gluten issue, we have all heard shared fryers are a big no-no. Nobody ever tested the theory, we all just assumed this was accurate. Makes sense right, cook gluten in one thing and cook something gluten free in the same oil and gluten contamination is likely to occur. Well, some smart people looked at it and this is what they found.

What did the study say?

The scientists took two samples of French fries from 10 restaurants in California and Ohio. The fries were ordered with salt only.

Samples were taken on two consecutive nights. When the staff was questioned about the French fries, the researchers were told the fries were gluten free by the staff. Neither the oil nor the fries had any gluten containing ingredients.

The researchers then asked a follow up question to the staff at the restaurant about the fryers. None of the fryers were dedicated gluten free fryers. All fryers were used to fry gluten items – onion rings and chicken fingers were given as examples.

The samples were tested via sandwich ELSA and R5 ELSA. Each of the twenty samples were processed into smaller samples. So, each sample was broken down into six samples to be tested via the ELSA methods.

Note that in this real world example, the French fries and oil were not tested to be gluten free before the samples were taken. The scientists did have a control using flour and a microwave.


Fries from 6 of the 10 restaurants came up with quantifiable gluten. Five of the twenty samples would not be considered gluten free. Fifteen samples tested at less than 20ppm of gluten.

Also, note that there are some limitations on the ELSA testing to detect gluten molecules that have been heated. Each of these French fry orders have been heated and could skew the results of the gluten content lower than it actually is.


This is a real world example of the kind of testing that would really help those of use with celiac disease. It is great that this study confirms that shared fryers are not good for those with celiac disease.

You now know the risk of eating French fries out of a shared fryer. Eat at your own risk.

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