First of all, I know One Step isn't a recommended sanitizer! I'm switching to Star San in future - or maybe just reverting to bleach, which never let me down. But anyway, my question.
I did two brews last fall where I used One Step to sanitize my equipment, and, since it's supposed to be a no-rinse sanitizer, I didn't rinse it out! This was just about the only thing I did differently from other brews I've done in the past. I took the usual precautions to avoid oxidation - not splashing hot wort, siphoning carefully, and so on. Both beers - one was a spiced Christmas ale and the other an English IPA - were super delicious at about three to five weeks after bottling, but both began to taste stale after six weeks or so. The flavour I get in them isn't glaring like wet cardboard, but in other respects it seems to resemble oxidation. That is, it tastes flat, and the interesting hop/malt/spice characteristics of the beers started to get muted once the off-flavour developed.
I generally expect my beer to last much more than six weeks, and I was surprised to see this flavour develop. Naturally, I suspect that it has something to do with the One Step, since that's the only thing that I changed in my process when I did these two beers. So - pardon my junk science. I'm no chemist. But One Step supposedly turns to hydrogen peroxide when mixed with water. If I don't rinse it out, will hydrogen peroxide oxidize my beer? Does anyone know? I'm curious!