Racking After Copper Sulfate Treatment

[winters...@gmail.com]

I am considering treating about 225 gallons of cider with copper sulfate to eliminate h2s smell.  I am doing trials now to determine the minimal amounts needed.  My question is how long after treatment can I wait/should I wait before racking it?  If I don't rack it off for a few months, can it cause any serious problems?  Many thanks.

[Andrew Lea]

The wine making textbooks tend to advise racking and filtering within a
few days of treatment. This makes intuitive sense to me. You are
generating nominally insoluble copper-sulphide adducts which may not be
chemically and microbiologically stable long term, so you run the risk
of both sulphides and free copper dissolving back into the cider if the
cider sits there long-term.

You may like to consider using a copper citrate / bentonite material
such as Kupzit (whose data sheet also recommends racking and filtration
after 2 days).
https://morewinepro.com/products/kupzit-hydrogen-sulfide-remover.html

Andrew

--
near Oxford, UK
Wittenham Hill Cider Portal
www.cider.org.uk

[Handmade Cider]

Some of my immature (just finished fermentation) ciders have an edge of H2S and it generally passes in a few weeks. If you are planning on storing the cider then it may be worth not treating it for a while to see if it passes.

Denis 

Denis France   www.handmadecider.co.uk   07590 264804  Company. No. 07241330

White Label – Champion Farmhouse Cider, Bath & West Show 2015.

Spring Surprise - Cider of the Festival Chippenham Camra Beer Festival 2015 & 2014

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[winters...@gmail.com]

Dennis,

How does it escape over time?  I have this batch in a SS variable capacity tank right now with the lid sealed (pumped up).  Sure would welcome this.  My fermentation ended about 3-4 weeks ago.

[Wes Cherry]

The sulfur from H2S doesn’t go away.    It just transforms into other slightly less objectionable compounds, some of which have higher sensory thresholds.   It seems to go away but it’s lurking and can come back to haunt you.

The problem is in a reductive environment (either in stainless tanks or worse, in a capped bottle) the sulfur compounds can be reduced back to more obnoxious variants such as methyl mercaptan (rotten cabbage) or H2S.   What seems like a decent cider at bottling can turn into a stinky cesspool cider.

Treat H2S problems ASAP after fermentation completes.   If you don’t they will soon transform into disulfides which are very difficult to treat.   The treatments for disulfides (ascorbic acid + copper + activated carbon) can strip flavor and color.

Some more details:

https://www.etslabs.com/resources/publications/sulfide-analysis/technical-bulletin.aspx

Screen test to determine what sulfur compounds you have

http://www.apps.fst.vt.edu/extension/enology/downloads/HydrogenSufide.pdf

and US source for chems

http://www.wine-testing-supplies.com/Item/assembly11

Here’s another option for treatment.   I haven’t tried it.

http://www.scottlab.com/product-119.aspx

Despite all this, if the H2S aroma is very faint at the end of fermentation, I don’t worry about it.  I think a tiny bit of sulfides and disulfides can lend roundness and complexity to a cider.

-Wes

To post to this group, send email to cider-w...@googlegroups.com.

[Jason MacArthur]

I wanted to add another wrinkle to the convoluted topic of H2S, and that is that we often find, in bottle conditioned ciders, a sulfury note immediately after they carbonate in the bottle.  We typically find however, that this disappears within a few months.  This seems contrary to a great deal of the literature on the topic, since the cider in the bottle is not only on the "problematic" lees  but is in the reductive environment of a closed bottle.  My best guess is that the lees themselves are somehow reabsorbing the compound, and this makes me think there might be an advantage to not racking a recently completed and slightly stinky fermentation.  

Jason

[winters...@gmail.com]

A follow-up to my original question...

Will it effect the timing of the CuSO4 doing its thing if my cider is only about 45-48 degrees F when its dosed?  In another words, will it take longer or be less effective than if the cider were at a warmer temperature, say 55 degrees?

Many thanks.

G  

[winters...@gmail.com]

I guess my trials to determine the dosage were done at similar temperature (50), so I presume it will work about the same...  Still interested if anyone has any thoughts or comments on this.

[Andrew Lea]

A standard rule of thumb is that the rate of a simple chemical reaction increases for each 10C rise in temperature. Conversely it decreases in the same way as the temperature falls. I would expect that to apply here, at least so far as the initial formation of copper sulphide is concerned. However, because you are not dealing with just chemistry, but also the complexities of sensory perception above and below a threshold, and that isn't linear, the only sure judge of the situation has to be you. 

Andrew

Wittenham Hill Cider Portal
www.cider.org.uk

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[Andrew Lea]

Sorry I missed out the most important bit! Which is that the rate DOUBLES for each 10C rise in temperature, and conversely as the temperature falls. 

Apologies for incomplete information!

Andrew 

Wittenham Hill Cider Portal
www.cider.org.uk

[winters...@gmail.com]

Thank you so much, Andrew, for the input.  It helps me formulate better expectations on timing, etc.