Mcdonalds French fries are evidentially par fried and then frozen. To do this, the must coat in flour. It may have been the oil the above comment says but it is definitely the flour coated French fries they serve. Sad!
I went there hoping to eat their French fries. So i informed them i had an allergy and they told me the fries were in a seprate fryer and i thought great. Didnt turn out so great. The oil they use isn't 100% gluten free.