Oily substance on top of wine

[nicklausjames]

Cabernet sauv 13 gallons stored in demijohn. It just completed mlf, I removed the stopper and noticed an oilish substance on top. It almost looks lthe consistency of gasoline spilled in a mud puddle. I immediately sulfited the wine but the substance was still there today. I tasted and the wine tastes great. Any idea on what this is? And how to treat it?

 

[cintipam]

Just a wild guess, no experience, but I sometimes see rainbow effects like I think you are talking about from soap on top of water. How did you clean and rinse the demijohn? I'll be interested in other folks ideas.

Pam in cinti

 

[nicklausjames]

Good point it does look suspiciously like soap. Although I did not use any I am aware of in cleaning. It showed up after I took a sample with a wine thief or at least that is when I noticed it.

 

[JohnT]

I do not think that this is anything to worry about. It could be a number of things like residual oil from you press/destemmer, soap, etc.

I would just keep an eye on it and check if it getting worse going forward.