Adding Copper Sulphate, Correct Dosage

[Tom Dunn]

I have a few batches of stinky cider that has refused to fall in line even after splash racking and stirring with copper pipe -

I want to attempt adding Copper II Sulphate Pentahydrate to a tank to see the effects however it's very difficult to find information on a correct dosage, which I gather is quite important not only due to ruined cider taste, but the legal limit of 0.5ppm and the fact Copper Sulphate is a poison.

One site suggests adding 0.5ml of 0.1% solution per 4.5L of cider to reach 0.3ppm,

Now if I have 1,000L of cider I understand that I should add 109.5ml (0.5x219) of 0.1% solution, or to make it easier, 11ml of 1% solution to the cider.

To make that 1% solution i'm understanding I just add 10g of 100% Copper II Sulphate Pentahydrate to 1 Litre of water - I then pipette off 11ml from that one litre and add it to the cider.




Am I correct? It seems like an incredibly small amount of 1% solution for a 1000L batch.
Is the source reliable to provide 0.3ppm of Copper Sulphate?
What is the difference between copper sulphate and copper II sulphate and which to use?

Could someone who has added copper sulphate to their own ciders or wines please give me some advice,

Cheers,
Tom

[Andrew Lea]

On 31/12/2015 11:57, Tom Dunn wrote:
> I have a few batches of stinky cider that has refused to fall in line
> even after splash racking and stirring with copper pipe -

See the extract from my book below. Note in my last paragraph and as Wes
previously posted, that if this problem is long standing then the H2S
may have gone on to form even smellier disulphide compounds which can no
longer be remedied by simple copper treatment.

I suggest you do small test batches first. Don't treat 1000 litre of
cider all in one go without trials!

> What is the difference between copper sulphate and copper II sulphate
> and which to use?

The standard form of copper sulphate commercially available is Cupric II
Sulphate Pentahydrate (blue crystals). You are unlikely to be able to
buy anything else.

Andrew

--------

If your cider smells of rotten eggs, drains or is generally ‘unclean’
then it may have a sulphur taint. Unfortunately most volatile sulphur
compounds in fermented beverages are odour-active at very low levels,
even parts per trillion in some cases, so these can be very noticeable
even when present in minute amounts. Many ciders do smell slightly
sulphurous when in the course of active fermentation but this usually
disappears quickly at the end of fermentation. If it does not, excess
hydrogen sulphide (H2S) or a related compound may be the cause. This can
be tested by taking a small sample of the offending cider in a glass and
dropping a brightened copper penny or a piece of copper wire into the
sample. After 10 minutes or so, its aroma should be assessed against an
untreated control glass. If the offending aroma has disappeared or is
reduced, it is possible to treat the bulk cider by the addition of
copper (cupric) sulphate. This is a permitted practice for winemaking in
the EU but only very small amounts of copper are used. (Excess copper
can have adverse effects on both cider colour and flavour by encouraging
unwanted oxidation as described later.)

The addition required is one part per million which is an extremely
small amount to measure. The best way to do this is by ‘serial
dilution.’ For instance a 1% solution can be made up by dissolving 5 g
of copper sulphate (a flat level plastic teaspoon) in 500 ml of water. 5
ml of this solution (a level plastic teaspoon) can then be dispensed
into 50 litres of cider to give the required level. Wait a day to see
how well it has worked; one (or exceptionally two) further teaspoons may
be added if required. The copper combines with the hydrogen sulphide to
form cupric sulphide which is insoluble. It is also possible to buy
bentonite impregnated with copper salts (eg Kupzit) which does the same
job but minimises the amount of residual copper passing into the cider.

The chemistry of sulphur in wines and cider is exceedingly complex and
if disulphide compounds have been formed after some time in storage it
may be necessary to ‘reduce’ them before copper treatment by the prior
use of ascorbic acid (Vitamin C). A professional winemaking textbook
should be consulted for further details. It has been claimed that
sulphur taints were not so much of a problem in a previous era when
brass or bronze (copper alloy) fittings were common on tanks and
pipework, since the transient contact with the metal acted to remove
them. Some people nowadays even suggest running cider through a short
length of copper piping for this reason! The ultimate cause of such
flavours is generally yeast related and is connected with the metabolic
pathways for sulphur-containing amino acids. In some cases nitrogenous
nutrients added before fermentation, especially with some cultured
yeasts, will prevent the problem. Because there tend to be two peaks of
H2S production during fermentation, some authorities recommend ‘split’
additions of nutrients with half being added before fermentation and the
remainder after about one-third of the sugar has been consumed.


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

[Wes Cherry]

Check out wineadds.com for a copper addition calculator.   

According to that calculator:

For 0.3 ppm cu2+ into 1000 liters you need 30 ml 1% solution or 1.18g cuso4

(Remember that you have to account for the relative atomic weight of copper vs the sulftate+hydrate when making copper solutions.  The ppm refers to the copper ion concentration by weight, not the rest)

And as Andrew suggests, run a trial first using much smaller samples.

-'//es Cherry

Dragon's Head Cider

Vashon Island, Wa US

www.dragonsheadcider.com

--
--
Visit our website: http://www.ciderworkshop.com
 
You received this message because you are subscribed to the "Cider Workshop" Google Group.
By joining the Cider Workshop, you agree to abide by our principles. Please see http://www.ciderworkshop.com/resources_principles.html
---
You received this message because you are subscribed to the Google Groups "Cider Workshop" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cider-worksho...@googlegroups.com.
To post to this group, send email to cider-w...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Steve OConnor]

If I have understood correctly, one should use ascorbic acid first , then treat with copper sulphate?

[Jay Kenney]

I'm not a chemist, but here's what I learned when I had a batch get stinky a few years ago. Have the cider tested for presence of H2S, mercaptans, sulfides and disulfides. Copper sulphate will not treat disulfides--that's where the ascorbic acid comes into play, it breaks them down into simple sulfides that can be treated with copper sulphate. Don't use ascorbic acid unless you've got disulfides above the sensory threshold. Then do a copper trial. Then treat with copper. Confirm that you are below the legal limit in your jurisdiction. In the US, "The quantity of copper sulfate added (calculated as copper) must not exceed 6 parts copper per million parts of wine (6.0 mg/L). The residual level of copper in the finished wine must not exceed 1 part per million (1 mg/L). 21 CFR 184.1261 (GRAS)." 

1. Test cider

2. Treat with ascorbic acid if indicated by presence of disulfides

3. Conduct a copper treatment trial. 

4. Treat cider with copper sulfate

5. Test cider for compliance with jurisdictional limits

[Joe Barfield]

Here is the copper trial procedure as outlined in Winery Technology and Operations by Dr. Yair Margalit. I found it very useful and elegant. 

I also added a photo of an easy way to do a rapid copper test wherever you might find yourself. I made a bunch of key fobs from Romex wire. It's waaaay more pure than old pennies, and you aren't likely to accidentally spend them. If I ever encounter any of you all out there in the wild, don't be surprised if I hand over a few copper key fobs. It's not because I think you make stinky cider. I just consider it a useful and simple thing to have on hand. Plus, I like to think it's sort of like a badge identifying cider makers. 

Enjoy,

Joe Barfield

     

[Steve OConnor]

Gentlemen, thank you for the information.