How do MLF and Copper Sulfate Interact?

[Kcass]

Hi all,

My partner and I have added MLF nutrients to initiate MLF, this was a week ago now. We took a small sample yesterday for smell and flavour changes and noticed there was a very very mild sulfuric aroma. This went away once the wine had air for 20secs.

The sulfuric acid smell was worse before and we 'splash' racked it, then added copper sulfate. We thought it had gone but it seems to have, ever so slightly, remained.

Should we add another dose of Copper to the wine while we are still in MLF? Or just leave it till the MLF is finished and hope the smell dissipates with clarifying further down the track.

Cheers guys,

 

[jgmillr1]

There should not be a problem with incremental copper sulfate additions while doing MLF. Splashing the wine risks oxidation or introduction of favorable conditions for acetic acid bacteria to go to town. This is especially true since you should have a low sulfite level at this point to encourage the MLF.

Be careful not to add too much copper sulfate though or you will leave residual copper (toxic!) in solution. Add 0.75mL of the 1% solution per gallon (0.5ppm copper). If the odor is still present the next day, add another 0.75mL per gallon and keep doing this until the aroma is gone. This is much more controlled than trying to splash rack it away and doesn't come with the same oxidation risk.

 

[Kcass]

Hi there,
We were also wondering whether it would be safe to assume MLF was finished when the bubbles stopped?
Do we need a chromatography kit? They seem pretty pricey.

 

[jgmillr1]

MLF usually finishes for me in a 3-6 weeks, depending on temperature and pH. To be sure, you should invest in a chromatography kit. I've only had 1 wine that did not complete MLF and needed to be re-dosed, but the chromatography kit caught it. That is the most fool-proof way to check for completion. Of course, you can simply give it enough time and assume it has finished.

 

[Kcass]

Okay thanks jgmiller1!