I have found it useful to put all the emphasis on me. "Sorry, I have this issue with eating noises, so I'm going to step out for a bit". Nice people will generally pick up on this and work with me over time. I don't get so many defensive reactions any more.
I wouldn't dare say that to a colleague or friend, because although they might appear to take it well, I don't think I'd be doing our relationship any favors. I'd step out with an excuse instead.
But given my lifestyle, I almost never have to be around anybody who's eating, except in contexts in which I can't hear them eating (busy brunch, say).
