“Sulphide Detection and Treatments Regarding
Wine”
W.C. PAETZ
February 18, 2004 Michigan State University
Abstract:
During our lab exercise we completed the process of sensory
evaluation of sulphides and mercaptans in wine utilizing exclusively
aroma trials. After discerning that sulphide problems did exist
in our wine sample, we explored methods to identify, isolate and to
determine a plausible treatment protocol.
INTRODUCTION:
Sulfur dioxide is one of the most versatile of chemicals.(1)
It comes as close as anything to being recommended for all wines. It
has many properties which make it the exclusive additive of choice to
preserve and protect wines during every aspect of the making of wines.
Sulphur dioxide has become such a universal additive because it has
four quite distinct properties.(2)
1.) Antioxidant the prime reason behindtis anti-oxidant property is
the fact that it will readily combine with oxygen, thus removing it
before too much harm can be done.
2.) Antiseptic (anti-microbial) Septic wounds are caused by bacteria
infecting the surrounding tissue, where they can flourish in the warmth
and the damp nutritious surroundings. When an antiseptic is applied
to a wound, the bacteria are killed. Sulphur dioxide has the same effecto
on bacteria in wine.
3.) Anti-oxidasic : The third property of sulphur dioxide relates to
enzymes. These are catalysts to change in the browning and degradation
of fruit substances and phenolics. Enzymes are named by words ending
in –ase; thus enzymes that promote oxidation are known as oxidasess.
Sulphur dioxide ascts as a poison to the oxidases, greatly reducing
the rate of oxidation.
4.) Corrective after oxidation: The first three properties of sulphur
dixode are all preventative, it is also corrective, in that it can freshen
tired wines which have been badly handled and have lost their intire
free SO2.
It is often administered prior to fermentation to inhibit wild yeasts
and to protect a wine from spoiled fruit and oxidation. SO2 is applied
whenever a wine is exposed to oxygen such as during a racking when the
wine is moved off sediments and might be exposed to contamination growth.
It is used prior to bottling to protect and preserve the wine. It is
rather ironic that this chemical which has such positive aspects, also
has a dark side. It is important to note that during a primary fermentation
the wine is protected by a blanket of CO2. At this time it would be
inadvisable to add any SO2. Doing so would needlessly promote SO2 in
its bound form, which would offer no protection to the wine and the
production of acetaldehyde may ensue.
SO2 or Sulfites are a good thing. Sulfides and Mercaptans are odoriferous
compounds which can ruin the desirable characters of wine. H2S or the
rotten egg smell may be present in a wine. Poly-Mercaptans represents
too much saturation of sulfur compounds and can be detrimental to wine.
Mono-Mercaptans and H2S are problems but are treatable. What if the
wine bouquet was comprised of cauliflower or onions? Being able to identify
and treat sulfur problems is a key role and an inevitable one for every
wine maker.
Materials and Methods
1.) Equipment:
1.) Wine Sample Pinot gris
2.) Five glasses
3.) Cadmium Sulfate
4.) Copper Sulfate
5.) Copper and Ascorbic Acid
6.) 50 ML beaker
7.) Pipette
Method:
1.) Measure 25 – 50 ml of wine to be tested
2.) Pour sample in five glasses
3.) One glass left as control sample
4.) Glass two 5 drops of cadmium sulfate
5.) Glass three 5 drops copper sulfate
6.) Glass four ½ to 1 ml of ascorbic acid, after several minutes
an addition of 5 drops copper sulfate added to this glass.
7.) Smell control sample
8.) Smell each sample in succession paying attention to changes in olfactory
sulfur character.
9.) Cadmium is poisonous …aroma test only!
Results
Please see appendix.
Discussion
Ascorbic Acid is an anti-oxidant which has been used as a partial substitute
for sulfur dioxide. Its best use is in the treatment of wine that has
had some H2S progress to disulfides. Using .25 grams per gallon will
cause the disulfides to revert back to mercaptans, albeit slowly, which
can then be dealt with using copper or bocksin.
Bocksin is a material used to eliminate or reduce hydrogen sulfide and
mercaptan odors in wine without having to resort to the use of copper
except when fairly high levels are present. Typical usage is 2 to 6
ml per gallon. Duration of the treatment is 24 to 48 hours with vigorous
mixing at least four times per day. A bench test is the best practice
to follow to discern how much. The treated wine should then be filtered
to .45 mu before it is tasted following treatment. It is compatible
with copper sulfate should that treatment still be necessary.
Copper sulfate is used to remove hydrogen sulfide and mercaptans. Use
a bench test to determine minimum effective dose. Avoid adding excessive
copper. This should only be done if aeration and racking do not solve
the rotten egg smell.
Another treatment, which might work, is carbon activated deodorizing
fining material. A bench test should be conducted. This will remove
odors and some color in wine. It is non-selective so both desirable
and non-desirable odors are removed.
Conclusion
This study was not only worth while but extremely important. The question
regarding adverse consequences from the formation of sulfide compounds
is one we shall all have to face.
Appendix
1 2 3 4
A. n/c odor gone odor gone odor gone
B n/c n/c odor gone odor gone
C n/c n/c n/c odor gone
D n/c odor less odor gone odor gone
E n/c n/c odor less 2 odor less 3
F n/c oder less 1 odor less 2 oder less 3
G n/c n/c n/c n/c
A = H2S present
B = Mercaptans present
C = Disulfides present
D = H2S plus Mercaptans
E = Mercaptans & Disulfides both present **********
F = H2S, Mercaptans and disulfides are all present
G = Odor not caused by sulfide compounds
References:
1.) Presque Isle Wine Cellars Doug Moorhead , Marc Boettcher Wine Making
Supplies Catalog 23 published 2003-2004
2.) D.Bird, Understanding Wine Technology The Science of Wine Explained.
The Wine Appreciation Guild, San Francisco 2002.DBQA Publishing
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