So- had a three gallon batch of cider I bottled last week. Fermented out all the way after a few months and tasted great. My dad took a few bottles home and tried one last night. It tasted like vinegar. So- I opened one too. Vinegar!!!!
I sanitized bottles just like I do with my beers. Used star San.
The ABV is 8%...... Thought that would have killed anything during transfer to bottle bucket...... What happened? I've made lots of cider, but have never had this happen....
The microb reaponsable actually converts the alcohol to the vinegear molecule so it has a very high alcohol tolerance. Make sure there are no fruit flies around your equipment as they tend to have the bacteria on them.
When I made apple wine it would get vingeary sometimes from the apple skins if I tried adding them after the open air fermentation. You could try sanatizing the outsides of the apple like you would your equipment before adding them.