If you have a sensitivity to zein know that it is the prolamine protein found in corn also known as corn gluten. This is not chemically identical to wheat or other glutens. 

It is hard to find a good substitute for corn and you must read labels carefully as it shows up as corn starch, high fructose corn syrup, corn oil, corn syrup,  corn gluten, dextrose, and malt syrup. It can found in baking powder, caramel (made from corn syrup), confectioner’s sugar, vanilla extract, and some time release medications.

According to Hope Jahren, a researcher at the University of Hawaii, and co-author of a new study that sampled almost 500 fast food items from McDonald's, Wendy's and Burger King proved that the vast majority of fast food meat is derived from animals that are fed corn/grains which is not their natural diet. This can affect the quality of the meat as well as possibly pose a problem to individuals that are allergic to corn/other grains. In lieu of this I would recommend buying grass fed beef if possible and staying away from most fast food chains while off zein.