Re: Hydrogen Sulfide - Rotten Egg Smell in Sauvigon Blanc

Frank Bacon wrote:
I fermented two batches of wine from Sauvignon Blanc grapes in September using two different type of yeast, one dry and one semi dry. The dry batch still reeks of Hydrogen Sulfide after repeated rackings. I used isinglass in the wine and its crystal clear but still smells like rotten eggs! Is there anything I can do to get rid of the foul odor? Will is dissipate with time?



Commercial wineries use copper sulfate for this purpose, but too much copper sulfate is toxic, so it must be done with caution. Also, some of the sulfur may be present in disulfide form, which smells like garlic or cooked cabbage. The disulfide form requires additional treatment.

Good Luck,
Gene

One of our well-respected members, Lum Eisenman, posted in Feb 2006 on H2S treatment (see below):

Subject: Re: Can H2S be measured?
From: "Lum Eisenman" <w.eisenman@xxxxxxxxxxxxx>
Date: Fri, 03 Feb 2006 00:03:33 GMT
Newsgroups: rec.crafts.winemaking

"Igor" <igorcarajo@xxxxxxxxx> wrote in message
news:1138916529.289952.289390@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

>> If you wanted to treat the H2S problem with CuSO4, it would be good
>> to know how much H2S you have, so that you can calculate how much
>> CuSO4 you need. Otherwise, how do you know how much to add?
>>

Igor,

A simple way of removing H2S is to add enough copper sulfate to produce about 0.1 ppm of copper in the wine. Then the wine should be stirred thoroughly, and after a few minutes, the wine should be carefully smelled. One treatment is often enough, but a second or even a third treatment may be necessary for difficult cases. The wine should be left undisturbed for several days after treatment so the copper sulfide (a very fine black powder) will settle to the bottom of the container. Then the wine should be carefully racked off the copper sulfide residue.

The following rules should be observed when using copper to remove hydrogen sulfide odors from wine. (1) Never add copper to active fermentations. Copper sulfate added during fermentation may cause more hydrogen sulfide to be formed. (2) Only very small quantities of copper sulfate solution are required, so use a pipette and measure carefully. (3) Add the 1% copper sulfate in small (0.1 ppm) doses rather than a single large dose. Very little copper will remain in the wine when copper sulfate is used in this way. More copper can be added if needed, but excessive amounts of copper are difficult to remove from wine. (4) Never add more than 0.5 ppm of copper to any wine.

Lum
Del Mar, California, USA


IN AUGUST 2006, LUM ALSO POSTED:

Winemakers use one percent copper sulfate solutions ( 1 gram copper
sulfate in 99 milliliters of water) to remove H2S and mercaptan stench from wine.

The reaction is very quick. Put 50 ml or wine in a glass, add a drop of
1% solution and stir. If the stench does not disappear, it is _not_ H2S or mercaptan. More info here
http://www.sdaws.org/Articles/Article4.htm


FOR DISULFIDE TREATMENT, LUM POSTED IN AUGUST 2006:

The "third structure" is disulfide.

H2S is a stinky gas. If the H2S is not removed from the wine in a few
weeks, the H2S will react with alcohol in the wine and form mercaptan. If the wine containing mercaptan is aerated, the mercaptan will form disulfide. H2S and mercaptan will react with copper and form copper sulfide. Copper sulfide is a solid. It has no odor and it precipitates out of the wine.
Unfortunately, copper will not react with disulfide directly. But, ascorbic acid (vitamin "C") is sometimes added to wines containing disulfide. The ascorbic acid breaks the disulfide bond and converts the disulfide back into mercaptan. Then the mercaptan can be removed with copper.

BUT, the ascorbic acid-disulfide reaction time is very slow (months not
weeks). So, treating a wine containing disulfide can be a very frustrating process and many winemakers give up too soon.
.

Relevant Pages

  • Re: H2s odor still lingering
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    (rec.crafts.winemaking)
  • Re: wine, hydrogen sulfide, copper sulfate
    ... "if you have a glass of wine showing some of these rotten egg, ... copper than newer ones and work better. ... <END QUOTE> ...
    (sci.chem)