It is my understanding that almost all citric acid used in the US is derived from corn. This was my last holdout in relation to going corn free and I am about to give it up to see if it improves my current problems (which do seem to be very suspiciously like the reaction I had to corn on my elimination diet).
I would suggest browsing in the Delphi Avoiding Corn forum. I don't know the link but you can Google it.
Also, check out the list of corn and gluten free foods at
http://corn-freefoods.blogspot.com/2007/05...s-of-51607.htmlI'm not sure that this is an exhaustive list of all safe foods, but corn and gluten free cuts out most of the prepared/prepackaged stuff if you truly go completely corn free (which, as someone else mentioned, not everyone needs to do).
There is also a list of corn derived and corn based ingredients on corn allergen.com
http://www.cornallergens.com/list/corn-allergen-list.phpI hope some of that is helpful.
One other thought, do you use Splenda? I just found out from my mother that it is made from corn. No wonder that new Diet Coke with Splenda was a really bad experience for me.