I have never caught an eel on a boilie, hopefully, that's just luck on the waters that I fish, because I do know of eels being caught on all manner of baits, including maize and tigers.
I think that eels in certain lakes will eat anything, whereas in other lakes they will stick to bloodworm or fish.
If you're unlucky enough to fish a water where the eels will eat anything, then I don't think you'll stop them by changing your boilie recipe.