Vinegar smell within a week

[hlmbrwng]

I haven't really been messing with my sours in the basement. One of the larger batches (about 6 gal in a 6.5 gal carboy) was starter from dregs of a Quetsche Tilquin bottle. The starter smelled amazing, and the first time I took a little whiff from the carboy, it smells really nice like the actual Tilquin. Then a few months I noticed lots of fruit flies in the airlock...none got past the star san inside. I replaced the airlock with another one dedicated to sours.

I took a whiff while I was changing the air lock. I noticed the Tilquin aroma was faded and there was a slight off flavor. It was one that I imagine will go away with time. I didn't really smell any vinegar aroma.
Well, today I was nosy (only a week after changing the airlock) while I was in the basement and took another whiff. This time I smelled predominantly vinegar.

My question: Is it because a lot of oxygen must have gotten in a made the whole batch sour? Or is it possible acetic acid has been produced at the top since the oxygen has to diffuse through the top of the beer first (i.e. it's not necessarily the whole batch)? I realize that it also could be something like acetobacter that was introduced when I switch the airlock. Perhaps a dead fruit fly fell into the carboy.

What are opinions about how much oxygen one can let in before it really becomes a problem. I am using a glass carboy. There is some headspace, but I (try to) flush out oxygen with CO2 in the carboy.

 

[hlmbrwng]

I guess the first sentence doesn't go with the rest...I suppose I am indeed messing with at least one of my sours in the basement. :/

 

[hlmbrwng]

I've decided to put my sours in kegs. Each has been aging for almost 4 months. The sour I am referring to above is my least favorite. I tasted each one while I had the opportunity during the transfer. But, it has been less than half a year, so who knows what it will end up like. And this was the one I was most excited about, since I harvested microbes from a sour beer I really enjoyed. I realize there are so many factors involved that there is no guarantee that they will turn out identical or even remotely similar. This has been a good lesson for me.

It isn't vinegary like I first thought. It has aroma of apple (almost cider) and of white wine (I'm not good with grapes varieties, so that's the best I can do with a descriptor). It may benefit from oak.

 

[Dcpcooks]

It's hard to tell what's going on with out a taste. It doesn't take much contact from fruit flies to create acetobacter my experience.

My best advise is to leave the sours alone at all costs. I use barrels for my sours and a bit of oxygen is expected along the way. So I've found most problems occur from dry air locks, fruit flies or during transfers.