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Organic Winemaking - Copper sulphate
March Sunday 21 2010
This is my reply to Herb Gardner asking for my input to the proposed new Australian Organic Standard.
Well it''s interesting that you have asked me about this topic. I have never used copper sulphate on any organic wine I have produced however I have seen numerous batches of organic wine over the years that would most certainly have benefited from a small addition of copper sulphate.
Now copper sulphate is used routinely in conventional winemaking to remove off flavours and aromas, mostly in red wines, called hydrogen sulphide and mercaptins. These undesireable characters usually occur near the end of fermentation as a result of the yeast struggling for sufficient nutrients particularly nitrogen. Organic grapes are notorious for being deficient in nitrogen, which is widely documented worldwide, plus of course DAP is banned in organic winemaking, which is used in conventional winemaking to correct this deficiency in nitrogen deficient musts.
There are differing standards around the world as to the allowable limits in bottled wine for traces of copper as copper is toxic to the human body at certain levels.
So back to copper sulphate....If added to wine at the levels recommended in the Australian Food Standards Code to correct the faults mentioned above then there would be no detectable traces of copper in the finished wine as the copper combines with the hydrogen sulphide and mercaptins to form a fine black inert deposit which would be filtered out of the wine before bottling. It is interesting to note that most Australian wines have minute traces of copper in them but at levels that the Australian Standard deems safe for human consumption. The only time there would be a problem would be if excessive amounts of copper sulphate was added. Yes the USA standard calls for zero detectable traces of copper in bottled wine and in fact I have personally seen some extremely large batches of conventionally made Australian wine rejected for export to the USA due to this reason in spite of the fact that no copper sulphate was ever added to the wine. So where can the copper come from? well it can come from the vineyard from the use of copper sprays, which is now not permitted in Organic viticulture, plus it can be introduced in the winery through the use of brass pumps and hose fittings. This is not common nowdays but most wineries still have some brass fittings in use. Traditionally in France where brass fittings were in common use they never saw the need to use copper sulphate in wine as every batch automatically received a minute dose of copper from the hose fittings!! This is widely documented in scientific literature.
I am not aware of any studies having been conducted to survey the levels of copper in finished wine either here in Australia or anywhere else for that matter. This would be a very interesting study for a PhD thesis!!
So what is the best approach for organic winemaking? Well at the end of the day banning the use of copper sulphate does not really solve any issues that benefit the "the interests of a vibrant and growing organic wine and grape growing sector for Australia". It is my opinion that a better approach would be to place a limit on the detectable traces of free copper in the finished organic wine...even if that was deemed to be zero that would still be OK as a skilled winemaker could use copper sulphate to correct faults but not in fact leave any traceable amounts of copper in the wine. The determination of how much copper to add to a wine to correct a fault is something that is within the scope and ability of even the smallest wine laboratory and winemaker but the determination of the traces of copper in finished wine needs to be done in a well equiped NATA certified laboratory.
So my final word on the matter is YES allow the use of copper sulphate in Organic winemaking but limit the level say even to half of the Australian standard or better still simply write into the Organic Standard that there should be zero detectable copper in finished Organic wine.
Well it''s interesting that you have asked me about this topic. I have never used copper sulphate on any organic wine I have produced however I have seen numerous batches of organic wine over the years that would most certainly have benefited from a small addition of copper sulphate.
Now copper sulphate is used routinely in conventional winemaking to remove off flavours and aromas, mostly in red wines, called hydrogen sulphide and mercaptins. These undesireable characters usually occur near the end of fermentation as a result of the yeast struggling for sufficient nutrients particularly nitrogen. Organic grapes are notorious for being deficient in nitrogen, which is widely documented worldwide, plus of course DAP is banned in organic winemaking, which is used in conventional winemaking to correct this deficiency in nitrogen deficient musts.
There are differing standards around the world as to the allowable limits in bottled wine for traces of copper as copper is toxic to the human body at certain levels.
So back to copper sulphate....If added to wine at the levels recommended in the Australian Food Standards Code to correct the faults mentioned above then there would be no detectable traces of copper in the finished wine as the copper combines with the hydrogen sulphide and mercaptins to form a fine black inert deposit which would be filtered out of the wine before bottling. It is interesting to note that most Australian wines have minute traces of copper in them but at levels that the Australian Standard deems safe for human consumption. The only time there would be a problem would be if excessive amounts of copper sulphate was added. Yes the USA standard calls for zero detectable traces of copper in bottled wine and in fact I have personally seen some extremely large batches of conventionally made Australian wine rejected for export to the USA due to this reason in spite of the fact that no copper sulphate was ever added to the wine. So where can the copper come from? well it can come from the vineyard from the use of copper sprays, which is now not permitted in Organic viticulture, plus it can be introduced in the winery through the use of brass pumps and hose fittings. This is not common nowdays but most wineries still have some brass fittings in use. Traditionally in France where brass fittings were in common use they never saw the need to use copper sulphate in wine as every batch automatically received a minute dose of copper from the hose fittings!! This is widely documented in scientific literature.
I am not aware of any studies having been conducted to survey the levels of copper in finished wine either here in Australia or anywhere else for that matter. This would be a very interesting study for a PhD thesis!!
So what is the best approach for organic winemaking? Well at the end of the day banning the use of copper sulphate does not really solve any issues that benefit the "the interests of a vibrant and growing organic wine and grape growing sector for Australia". It is my opinion that a better approach would be to place a limit on the detectable traces of free copper in the finished organic wine...even if that was deemed to be zero that would still be OK as a skilled winemaker could use copper sulphate to correct faults but not in fact leave any traceable amounts of copper in the wine. The determination of how much copper to add to a wine to correct a fault is something that is within the scope and ability of even the smallest wine laboratory and winemaker but the determination of the traces of copper in finished wine needs to be done in a well equiped NATA certified laboratory.
So my final word on the matter is YES allow the use of copper sulphate in Organic winemaking but limit the level say even to half of the Australian standard or better still simply write into the Organic Standard that there should be zero detectable copper in finished Organic wine.