What kind of juice goes sour?

OJ and apple go sour but if they were frozen, they shouldn’t go sour in the freezer.

Just curious, did you taste the juices before you made the popsicles? It seems like one of them had to be sour before you froze them.

Well it was purple so it was grape or cranberry.

My guess would be cranberry.

I think I found the culprit. I bought a large bottle of grape juice. It’s been sitting, open, for quite a while. I usually use the small individual juices.

Fresh juice will spoil pretty fast. Pasteurized juice will last quite a bit longer.

Im surprised they taste pickly. Usually, juice will ferment and become boozy/bubbly. You said open though, as in no top? That might do it, still its weird. My thought was contaminated popsicle molds. Plastic can hold a smell for a while.

I think you need to taste the bad juice to confirm the source of the flavor. Inquiring minds want to know.

The cap was still on. It’s gone now.

I’m not sure if it’s juice as such, but coconut milk definitely goes sour. Especially if the coconut flesh inside is green mouldy. I speak from experience.