I have a one gallon jug of Merlot from 2003 that has went bad. It has been separated from the rest of the batch for some time so thankfully the bulk of this batch is fine. Unfortunately I was a bit lax in my note keeping and labeling on this one and had just marked it to keep separate because of off-flavors but that's about it. I believe this is a jug that the airlock went dry on earlier in its career, but not positive about this -anyway it had a white film on surface and now has a very sour, undrinkable taste.
The strangest thing about it is that it has stained the inside of the jug purple with a thick purple hardened coating. Anyone seen this before and know what causes it?
Is it possible that it has started to turn to vinegar and if so, or not, can I make vinegar out of it?