Made a very tasty american pilsner 6 months ago Haven't had one in a couple months. Just opened one of the last ones and it was vinegary. Why would this happen? Thanks.
Yeah, probably an infection, especially a bacteria called Acetobacter. It might just be a bad bottle (didn't get cleaned well) but if the others also taste like this I would review your cleaning/sanitation. Acetobacter also requires oxygen so try to see if there is any place you are getting too much air into your beer, for example raking or bottling.
so acetobacter would take time to develop and that's why the beer tasted good for 2 months? You guys are right. I have a problem where I feel I have to save the good beer I make so I can enjoy it. Now I may be pouring it away.