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Copper-6? Copper unsafe for distilling?


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I was on a drinks and cocktail forum and saw an unrelated discussion about copper vs. other substances and someone posted the following. I researched it and can find nothing to back it up. What do you think?

"I would try to avoid using copper on food preparation, same as aluminum.

I recently have been told by Santa Teresa's chief master distiller that copper it is actually not allwed for distillation since a few years back, for it is proved that with the use small particles of copper change their chemical composition to something called copper-6 which in turn it is dangerous for human ingestion.

You may wonder why this is said but several drinks are distilled in copper pot stills and some of them even marketed it. Well, a lot of money goes around in the drinks industry, there are a lot of unknown things for regular consumers that drinks company do, even concerned with the ageing time stated on labels far beyond that the rule of "the youngest blend is the stated one"."

http://groups.msn.com/DrinkBoy/general.msn...655441949364887

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Posed the question to a knowledgeable friend, here's his response...

"Never heard of it. Copper can be +2 (mostly) and some +1, very rare to be +3 or +4. So I got no idea what they might be referring to. Did searching and only found the ADI forum mention and the MSN citation that was the source. Not a good sign to indicate it being real. The phrasing of the quote is odd in a way that rumors and spoofs are. The Santa Teresa's chief master distiller said that copper wasn't allowed but doesn't say by who or how (or if only applies to Venezuela). Then makes a contradictory statement that the industry does it any way, either braking the law or they prevented the prohibition of it's use which he just said existed. Typical claim of evil money does bad for people; this claim is frequently true so it makes it believable, people easily suspect it to be true so it makes that theme an easy spoof. Then claims they are many other things the industry does but only mentions a trivial one. Again industry is an easy suspect, like propylene glycol has been found in food and beverage. But with being so brief and lacking detail I would suspect spoof. If it was real and the poster seems that worried they would have provided more info. You might give a look and see if you could find who the master distiller is and send an email."

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I think this is a red herring. Cu(6+)? Someone's watched Erin Brokovich too many times.

Some things to consider:

Most metals are required in small amounts and toxic in large amounts. What counts as 'large' or 'small' depends on which metal.

As far as I can tell, there's no such thing as hexavalent copper. I was only aware of Cu(1+) and Cu(2+), and even wikipedia, that source of all misinformation only admits to 3+ and 4+, and those being rare and unstable.

The same wikipedia article notes a maxium daily intake of 10mg/day. That's milligrams, not micrograms. Or a drinking water level of 1-2 ppm.

Copper has been historically used in stills (though that doesn't make it safe), and Cu metal treaters are added to kirsh stills on purpose to reduce amygdalin levels.

Copper is not bio-accumulative - it doesn't build up. There are health problems with acute levels and with deficiencies. Some Cu salts are poisonous. Some plankton level microorganisms can't tolerate copper. (I was a biology student at a college in a copper mining area - nothing grew on the stamp sand deposits, and there is a 'dead' zone of a meter or so right near the sands where they run into lakes. on the other hand, Cu in the ground water wasn't an issue, but Arsenic was.)

There was a comparison to aluminum, where there is supposed to be a causitive relation with certain kinds of dementia. Cu is not Al (with Cu, there _may_ be a relation with schizophrenia - but it isn't known if it's cause or effect). Secondly, think of the mechanics involved - with Al cookware, you're heating an acidic solution in the pot and transferring it to the plate. In distilling, most mash or wash isn't very acidic (unless you're making kirsh) - and it stays in the pot. Distilling _removes_ ions. They all end up in the counterflow, back in the pot and sent down the drain. If protein, tannins, sugars don't make it through the still, how are metal ions going to? this doubly applies to the suggested mechanism - reactions with particulates.

Most folks with modern stills have stainless steel condensers/product chillers - so there's no hazard from Cu when the spirit is back in liquid form.

Most plumbing is copper - including hot water. in fact, here where i am in Wisconsin, there's push from the health inspectors to get rid of the alternative - they don' like the Cl in PVC.

So keep those pots free of corrosion (those salts, which can be toxic) and ask doubters for hard data.

Charles McGonegal

Chemist II

UOP, LLC

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Since the original poster commented that they were avoiding both copper AND aluminum, I put them down as just simply being a tad over-protective.

I've seen nothing about copper toxicity, but am quite familiar with the "wives tales" about aluminum. Ok, not quite a wives tale, but the quick details are that there was a study of the brains of alzheimer patients which made note of a slightly high concentration of aluminum. They didn't attempt to say that aluminum could be a cause of alzheimers, only that it was present... of course folks jumped to conclusions and quickly through out their aluminum cookware and stopped using deoderants which contained aluminum... a second study was done to try to get a better understanding... this time however there was no indication of any abnormal aluminum concentration. After a little bit of detective work, they discovered that in the original study the dye which the researchers were using to stain the brains for observations included aluminum... :->

-Robert

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"I would try to avoid using copper on food preparation, same as aluminum.

I recently have been told by Santa Teresa's chief master distiller that copper it is actually not allwed for distillation since a few years back, for it is proved that with the use small particles of copper change their chemical composition to something called copper-6 which in turn it is dangerous for human ingestion.

I think this discussion is really about ethyl carbamate. Copper is a precursor to the production of the carcinogen ethyl carbamate. There are world standards to manage and lower the levels of ethyl carbamate, originally identified in the UK scotch industry. This debate created the incorrect perception that copper was the culprit, I quote the UK food standards,

Research on whisky has shown that ethyl carbamate is formed during distillation and using the right barley varieties and distillation conditions are the key control parameters.As a result, since the early 1990's the Scotch whisky industry has taken steps to reduce the level of ethyl carbamate in whiskies by selecting barley varieties with naturally low levels of precursors of ethyl carbamate.

Studies have also shown that copper catalyses the formation of ethyl carbamate during the traditional double distillation procedure used in the manufacture of Scotch whisky. If copper contact can be maximised early on in the distillation to promote ethyl carbamate formation from its precursor, the non-volatile ethyl carbamate is not distilled over into the spirit. The industry has gone to considerable length to ensure that the spirit is in contact with copper for as long as possible. For example, distillation of grain spirit is typically carried out in the presence of sacrificial copper. Likewise, a third distillation, as occurs in the production of Irish whiskey, will also help ensure that ethyl carbamate levels are low.

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I love copper, why copper is good;

  • Its proven, over 400 years of faultless service
  • Its one of the best thermal conductors around
  • Its stable, self pacifing and easy to clean
  • It looks good, its tradditional
  • It is essential in the fixing of various esters and volatiles during distillation
  • Its easily recylable (not that you would !!!)
  • Its stable under direct flame, and in the presence of most CIP agents
  • Did I mention it looks good

What I hate about copper;

  • Its expensive, and getting more so because of the escalating world demand
  • Its a bastard to weld
  • It tarnishes
  • Good coppersmiths are a dying breed, and few are entering the trade

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Rich, I suspect you're right about the ethyl carbamate (aka urethane). A quick search shows not only the whiskey research that you mentioned, but also issues with Brazilian cane spirits - so that ties back nicely to the original article. I've yet to have a journalist quote me accurately.

On the wine side of things, ethyl carbamate tends to form from left over urea - which usually comes from the metabolism of certain amino acids. Copper doesn't seem to play much of a role in that pathway.

But for distillers, copper catalysizes reactions with cyanates to make ethyl carbamate. An important consideration for stone fruit distillates.

I think it's interesting that the cure is to apply more of the 'problem'. More copper, drive the reaction to completion and the carbamate stays in the pot, rather than forming from precursors later on.

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Rich, I suspect you're right about the ethyl carbamate (aka urethane). A quick search shows not only the whiskey research that you mentioned, but also issues with Brazilian cane spirits - so that ties back nicely to the original article. I've yet to have a journalist quote me accurately.

On the wine side of things, ethyl carbamate tends to form from left over urea - which usually comes from the metabolism of certain amino acids. Copper doesn't seem to play much of a role in that pathway.

But for distillers, copper catalysizes reactions with cyanates to make ethyl carbamate. An important consideration for stone fruit distillates.

I think it's interesting that the cure is to apply more of the 'problem'. More copper, drive the reaction to completion and the carbamate stays in the pot, rather than forming from precursors later on.

[/quote

If anyone remembers the taste of Jim Beam before 1995, it had a very grassy taste, this must have been due to ethyl carbamate. I read somewhere tjat the levels were so high that some agency required them to put in some type of filter in 1995.

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Rich, I suspect you're right about the ethyl carbamate (aka urethane). A quick search shows not only the whiskey research that you mentioned, but also issues with Brazilian cane spirits - so that ties back nicely to the original article. I've yet to have a journalist quote me accurately.

On the wine side of things, ethyl carbamate tends to form from left over urea - which usually comes from the metabolism of certain amino acids. Copper doesn't seem to play much of a role in that pathway.

But for distillers, copper catalysizes reactions with cyanates to make ethyl carbamate. An important consideration for stone fruit distillates.

I think it's interesting that the cure is to apply more of the 'problem'. More copper, drive the reaction to completion and the carbamate stays in the pot, rather than forming from precursors later on.

Charles, agreed. I was working in Scotland in the late 90's when it all blew up over there. The trials we ran then (GC protocols for EC were not established yet) indicated that the 'leave it behind' methodology worked well.

When I started working up our current vodka, I sent 30 or so commercial samples to an analytical lab we use for full GC/MS/MS profiling, so as to establish a baseline. What was alarming was the incredibly high levels of EC in some of the vodka's, suggesting that it is not being monitored in a lot of countries. Here in Australia we have very strict controls, but I believe there are none in the former USSR states. The lesson, never drink anything from a continuous still.

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  • 2 weeks later...

The EC thing blew up in Kentucky at about the same time it blew up in Scotland. Ironically, American distillers had been experimenting with taking copper out of their stills, because of the cost. They weren't happy with the results, flavor-wise, and found that re-introducing copper solved the EC problem too.

As it was explained to me, copper contact has many salutary effects. Copper reacts with sulfides and keeps them in the still. The reaction creates a black film that has to be cleaned off every few days to keep the copper surfaces active.

All of the world's whiskey makers make sure their spirit gets plenty of copper contact and most whiskey distillers will tell you it's impossible to make good whiskey without copper.

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The EC thing blew up in Kentucky at about the same time it blew up in Scotland. Ironically, American distillers had been experimenting with taking copper out of their stills, because of the cost. They weren't happy with the results, flavor-wise, and found that re-introducing copper solved the EC problem too.

As it was explained to me, copper contact has many salutary effects. Copper reacts with sulfides and keeps them in the still. The reaction creates a black film that has to be cleaned off every few days to keep the copper surfaces active.

All of the world's whiskey makers make sure their spirit gets plenty of copper contact and most whiskey distillers will tell you it's impossible to make good whiskey without copper.

Our Holstein still which is all copper (and maybe the Christian Carl's too?) has a "catalytic convertor" right before the condensor that is I believe a group of tightly spaced copper plates to give additional copper surface area for contact with the vapor before it is recondensed. I'm wondering if it was the EC issue that prompted them to include it?

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Our Holstein still which is all copper (and maybe the Christian Carl's too?) has a "catalytic convertor" right before the condensor that is I believe a group of tightly spaced copper plates to give additional copper surface area for contact with the vapor before it is recondensed. I'm wondering if it was the EC issue that prompted them to include it?

Yes it was. Holstein's and Carl's traditional market include the fruit brandy distilleries of Germany and greater Europe, and stone fruit mashes produce a higher than normal EC level, so the catalytic converter was their answer to the new EU regulations on EC levels.

Copper is good.

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