I'm a bit late to the game here, but I thought I'd throw this out there. Baking soda. It reacts with acids, and apparently adding some to tomato sauce is a good way to smooth out the taste without having to add a lot of extra sugar, and also makes it milder for people who are prone to heartburn.
I'm not sure how this would work in something other than tomato sauce, but the chemistry is sound. The sodium bicarbonate would definitely react with lemon juice.
I've just been sharing this with everyone because I was so surprised that I'd never seen, heard or thought of it before (despite my mother's insistence that she's been doing it for years. She's completely on crack), and once my mom mentioned it, it seemed so obvious.