I opened a bottle of red wine (cabinet) about six months ago and there were about half of bottle remaining so I corked it back into the bottle. Last night I poured some out of the same bottle and it appears that the color of the wine has changed to deep darkish red/brown colour along with lots of particals. What is that and is it safe to drink in that condition. How do I prevent that from happening in the future? Maybe the cork’s mass is not air tight enough caused the wine to degrade? Is there a self life for wine after all?