Acetaldehyde in Xingu Black Beer?

My dad and I just shared a Xingu Black Beer from a bottle. He'd had it before and liked it, and I hadn't tried it before. It had what can only be described as a green apple taste. I was surprised to find this in a commercial beer. To my knowledge, it's not a bottle-conditioned beer, which suggests to me that the entire batch would be like this. Anyone else experienced something like this with a commercial beer? It doesn't seem like something that would be done on purpose.

... and now we're drinking a Samuel Smith's Taddy Porter and I'm getting the same thing. He says he doesn't taste it. Am I crazy?

It's possible you are perceiving the acidity from the roasted barley in these beers as acetaldehyde. While it's is not exactly a green apple flavor, it can be quite tart, and in the presence of any appreciable level of fruity esters, could give that impression.

Xingu is a somewhat complex drink. I love that stuff. Never noticed a sour apple note though.
I've found that it can taste slightly different from bottle to bottle.
I haven't had it in a while. Now that it comes in 6x12, I think I'll see if the same holds true.
Plus, now that eu jogo capoeira, it just seems fitting.
(That's Brazilian Portugues for "I ache all over".)

I'll need to try both of those beers again. It's possible that I was misinterpreting the taste. Maybe I'd eaten something earlier that was messing me up. I have a hunch, though, that neither beer was very fresh. We got them at a Total Wine and More store, and they're both imports. Could've been some less than ideal shipping/storage somewhere along the line.