Why does my lemon water start to taste FUNKY after it sits too long?

I have fresh squeezed lemon or lime juice in my kitchen almost constantly. I squeeze one at a time and slowly use its juice. I like to put it in smoothies and gin and tonics but also just in my water often as well.

Something I have noticed for years….when you add it to water, it tastes great for….roughly 4–6 hours I’d say. After that, some sort of chemical breakdown must happen, and it starts to taste WEIRD. Subtle, but I notice it, kinda like peroxide maybe. Very hard to explain. It is not rotten or BAD but it’s NOT pleasant and I dump it out, usually after making some dramatic facial expression. But, at this point, I’ve come to expect it, and try not to let it happen lol.

The thing I don’t understand is, the lemon or lime juice by itself lasts at least a day or two. I use it fast enough that I’ve never tested it beyond that so I can’t be sure. But, you add water to it, let it sit overnight for instance, and yuck. Does anyone know why this might be? Lots of extra time on my hands later has me wondering plenty of extra things, hehe.

BTW hi Fluther, it’s been a long time, hope youre all well :)