Removal of hydrogen sulfide - by copper or refermentation?

[Søren Ugilt Larsen]

Dear all,

I have two batches of cider batches which have developed sulphury smells at the later part of the fermentation process. I suppose the smell is due to hydrogen sulphide, since a test with addition of a piece of copper removed the sulphury smell effectively (according to the test suggested in Andrew Lea's book). 

Both batches were based on culinary apples, fermented by wild yeast, typically at 10-12C and without any addition of nutrients. One batch was based on apples harvested early October and with a relatively successful keeve and relatively slow fermentation. The other batch was from apples harvested early December, the must was sulphited with a quarter of the normal dose (pH 3.4, -> 21 ppm SO2) and with a rather poor keeve (poor formation of brown hat) and a relatively vigorous fermentation. Both batches appear slightly to moderately hazy by know. 

As for prevention of the H2S smell, from what I can read, there is increased risk of H2S formation when not adding fermentation nutrients, so this might have prevented it, however, addition of nutrients is somehow in conflict with the aim of having a slow fermentation?

As for removal of H2S, I understand that copper products such as Kupzit or Kupfat may solve the problem (Copper Citrate (Kupzit) 1kg - Vigo Ltd,

Copper sulphate (Kupfat) 500g - Vigo Ltd) (also some discussion on the topic in these treads: Filtration or Racking after Copper Treatment? (google.com), Referment of cider (google.com)). However, I also understand that it may be necessary with some precipitation of the excess copper and perhaps even filtration (which I do not have equipment for). Or could I avoid increasing the copper content of the final cider by using as low a dose as possible (by an initial test of various concentrations)?

Is it likel that the H2S smell could disappear during a refermentation of the cider, e.g. by addition of a little sugar (e.g. 10 g/L), fermentation nutrients (dose?) and a champagne yeast such as EC1118 (low in H2S production)?

Hope for some good suggestions - and sorry if the topic is already over-discussed :-).

Best wishes

Søren

[Andrew Lea]

II you have my book you can find directions for treatment with copper sulphate solution to remove H2S. It works and is simple to do. The amount you add is very small and in practice there is no need to worry about precipitation of excess copper.  

The other thing you could try is “splash-racking”, which may remove H2S simply by physical means.

There is no guarantee that re-fermentation will remove H2S since it is generated by yeast from amino acid precursors and is not re-metabolised (unlike ethyl acetate).

In my experience H2S problems when using a wild yeast are pretty minimal.  It’s only when you start to use nutrient-demanding cultured yeasts that H2S starts to become a problem.

Andrew

Wittenham Hill Cider Portal
www.cider.org.uk

On 23 May 2021, at 12:01, Søren Ugilt Larsen <sorenugi...@gmail.com> wrote:



--
--
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 view this discussion on the web, visit https://groups.google.com/d/msgid/cider-workshop/CANR-nxhh3wzyT9mgPNKjUZNkzBd3hnRYUJ28uP0kzNr1VPNCxw%40mail.gmail.com.

[Søren Ugilt Larsen]

Dear Andrew,

Thanks a lot for your advice. I certainly have your book and will follow the instructions on p.101. It is good to know that there is no risk of critical high levels of copper when applied in a controlled manner.

Is this treatment generally used in commercial cider production in case of H2S smell?

I have previously used champagne yeast in my cider production - is it likely, that this cultured champagne yeast may have 'carried over' somehow (on equipment etc.) into subsequent batches with wild fermentation and then may have become dominating in the later stages of the fermentation and caused the production of H2S?

As a first step, I may try the splash racking - although my wife is rather concerned about the implications of the concept! (she has recently repainted the kitchen ceiling after a small 'carbonation incidence'...) :-)

Best wishes

Søren

[Wayne Bush]

Hi Soren--just chiming in to say that I've used the "splash racking" and then waiting method that Andrew suggests above a couple of times, and both times that has solved the problem without having to go to the next step of a copper sulphate treatment.  I make sure that the cider gets well aerated during racking and then put some CO2 over the top of it and let it rest another couple months.  Regards, Wayne

[Søren Ugilt Larsen]

Dear Wayne, 

Thanks a lot - it sounds promising with the splash racking. I don't have CO2 to put on top of the cider, but I always try to minimize the headspace as much as possible, also to avoid acetobacter and oxidation, so I hope this will do.

Do you normally add SO2 in relation to splash racking to avoid oxidation and spoilage microbes?

Best wishes

Søren

[Wayne Bush]

Soren, yes--sorry I forgot to mention it, but yes I also added SO2.  I know a lot of people don't really like it and neither do I, but it prevents many bad things from happening to your cider.