Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Lewis Thomson on 15/01/2018 12:55:13
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Kalind asks:
I love making and drinking homemade wine from a variety of fruits like grapes, oranges, mango and so on. However, I am concerned about methanol contamination. Is it possible that the wine would get contaminated with methanol and prove to be fatal? If I want to check whether or not the methanol levels generated are within safe levels, what should I do? Is there a simple test available to detect the same?
What do you think?
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Elderberry wine is not to be recommended I once drank a bottle and was real ill for two days.
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Methanol is formed in very small amounts during fermentation of grape juice or cereal grains and there are very small amounts in wine and beer, but not enough to cause problems when these products are made at home. However, home distillation to make spirits concentrates levels of both ethanol and methanol which is where the danger occurs.
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There's actually always some methanol in wine. However, the medical treatment for methanol poisoning is ethanol which delays the processing of the methanol and stops its metabolites reaching toxic levels. Because wine contains plenty of ethanol, that means that wine is not much more toxic than the ethanol it contains. The main problem with home distillation is that it's reasonably easy to get it wrong, and if you do, you can accidentally concentrate the methanol more than the ethanol which can render you permanently blind or worse.
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However, home distillation to make spirits concentrates levels of both ethanol and methanol
So why doesn't this happen to the "professionals" too, or does it? Methanol boils at a lower temperature than ethanol (67C vs 78C) so I'd think it would be a problem for both home distillers and the experts?
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So why doesn't this happen to the "professionals" too, or does it? Methanol boils at a lower temperature than ethanol (67C vs 78C) so I'd think it would be a problem for both home distillers and the experts?
Home distillers, unless they know what they are doing, tend to use fairly unsophisticated systems with poor temp control. Many will boil the mash which boils off both the ethanol and methanol.
Professional systems use better temperature control so methanol boils off first, this first distilate known as the head is then discarded to be sold as a by product. Temperature is then increased to boil off the ethanol and other distilates which contribute flavours.
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Interesting; I didn't know that; so I wonder how much flavour is lost in the head?
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If you're doing a proper distillation, the only thing that gets collected should be ethanol. Other components relating to flavor (or odor) would have different boiling points. In order of boiling point:
acetaldehyde (20.2 °C) minor
acetone (56 °C) minor
methanol (65 °C) minor
ethyl acetate (77 °C) typically very minor, but is a component of pears, and due to the closeness to ethanol bp may well come over, giving pear brandy its distinct aroma
ethanol (78 °C) major
diacetyl (88 °C) minor
water (100 °C) major
acetic acid (118 °C) minor
So if you're making vodka, you just have to distill the ethanol out and dilute it to 40% with water and you're done.
Distilled spirits with more complex flavors are produced by different treatments.
I believe that gin is made in such a way that the ethanol vapors pass over the herbs and spices used to flavor it (added immediately after/during the final phases of distillation.
Whiskeys and brandies are often aged in wooden barrels after distillation. The wood breaks down partially, adding small aromatic molecules (lignin-derived) like vanillin (primary component in vanilla) and guaiacol (has a dark, smokey flavor--it's in dark roasted coffee, bacon, and anything else that's smoked, as well as "peaty" Scotch). With boiling points of 205 °C (guaiacol) and 285 °C (vanillin), there is no way that these could come over in the distillation. Oxygen is also slowly allowed to diffuse in through the wood, and the oxidized small molecules import their own flavors. Acetaldehyde (which boils at practically rt, so was not collected with ethanol from distillation) can form in traces from the oxidation of ethanol, and are partly responsible for the "bite" or "heat" of an aggressive whiskey. Also compounds like diacetyl can form, and give a "buttery" flavor.
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That's fascinating; thanks @chiralSPO for that detailed information.
So, dare I ask then, what the consequences could be for people using vacuum distillation techniques, like Will Lowe, who was on the Naked Scientists in 2016 to discuss the gin he makes from ants (yes, you read that correctly): https://www.thenakedscientists.com/articles/interviews/ant-flavoured-gin - and again more recently for Christmas - https://www.thenakedscientists.com/articles/interviews/christmas-tipple-theres-ant-my-gin
Will it be similarly simple to discard the methanol-rich fractions?
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Is homemade wine safe?
I heard a Chinese scientist explain the more common Chinese difficulty breaking down alcohol this way:
- In the past, it was dangerous to drink water from rivers
- In the West, they tended to disinfect it by mixing in wine (alcohol is a mild disinfectant). Many westerners have genes that break down alcohol fairly readily.
- In the East, they tended to disinfect it by brewing tea (boiling is an effective disinfectant). Fewer Asians have the genes that break down alcohol rapidly
So home-brewed wine is probably safer than medieval stream water
- but not as safe as modern treated tap water
- don't overdo the wine (especially if you lack the genes for it)
PS: Avoid storing wine in lead (a substance the Romans were very fond of...)
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I wonder how much flavour is lost in the head?
I understand that the head has an unpleasant odour so i dont think any good flavours are lost. The weak portion at the end - tail - is also discarded. The middle - heart - fraction is richest in aromas and flavours and used for the maturation process described by @chiralSPO .
For the finest brandies the distillation uses either fine wine or fruit wines - eg plum or peach wines. Cheaper brandies use blended nondescript wines which have fewer distinctive flavours.
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That's fascinating; thanks @chiralSPO for that detailed information.
So, dare I ask then, what the consequences could be for people using vacuum distillation techniques, like Will Lowe, who was on the Naked Scientists in 2016 to discuss the gin he makes from ants (yes, you read that correctly): https://www.thenakedscientists.com/articles/interviews/ant-flavoured-gin - and again more recently for Christmas - https://www.thenakedscientists.com/articles/interviews/christmas-tipple-theres-ant-my-gin
Will it be similarly simple to discard the methanol-rich fractions?
You're welcome. :)
Using a vacuum system won't change things too much other than decreasing the boiling points of all of the components (in a mostly monotonic way, though there is some funny business*) Reducing the pressure to about 10% of atmospheric pressure would allow the ethanol to boil with only mild heating, at about 30 °C, while methanol would spontaneously boil at temperatures above 18 °C, allowing for easy separation. (really, discussing boiling points is an oversimplification--we should think about vapor pressures of mixed solutions and fractional distillation: https://en.wikipedia.org/wiki/Fractional_distillation and I should also mention that there are such things as azeotropes, that make it very difficult to completely separate some mixtures: https://en.wikipedia.org/wiki/Azeotrope)
*For instance, at one atmosphere, toluene boils at 110 °C and water boils at 100 °C, but at 10% atmospheric pressure, toluene boils at 0 °C and water boils at 7 °C (this is a fairly interesting line of thought, but takes us away from the OP... I'd be happy to discuss this further in a new thread if someone likes.)
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From wine to recreational inhalants. Slippery slope. :o
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Reducing the pressure to about 10% of atmospheric pressure would allow the ethanol to boil with only mild heating, at about 30 °C,
This is an interesting point. Cognac and scotch whisky are distilled in copper stills at higher temperatures - legally they can only be made in a pot still and not in a distillation column.
Copper was originally used to manufacture pot stills because it is easy to shape, conducts heat easily and is resistant to corrosion. However, it does wear out and is expensive. Some distillers did experiment with stainless steel, but noticed a dramatic change in spirit quality – a sulphurous odour that had nothing to do with cut points or the speed at which the stills were run.
It soon became apparent that the acidity of the mix, temperature and clean copper inside the still is vital to allow various chemical reactions to take place, removing highly volatile sulphur compounds – chief among them dimethyl trisulphide or DMTS – and helping in the formation of esters, which tend to give the spirit a fruity character.
What im not sure about is exactly where the temperature of the ‘boil’ in the still has to be in order to ensure that these reactions take place.
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Reducing the pressure to about 10% of atmospheric pressure would allow the ethanol to boil with only mild heating, at about 30 °C,
This is an interesting point. Cognac and scotch whisky are distilled in copper stills at higher temperatures - legally they can only be made in a pot still and not in a distillation column.
Copper was originally used to manufacture pot stills because it is easy to shape, conducts heat easily and is resistant to corrosion. However, it does wear out and is expensive. Some distillers did experiment with stainless steel, but noticed a dramatic change in spirit quality – a sulphurous odour that had nothing to do with cut points or the speed at which the stills were run.
It soon became apparent that the acidity of the mix, temperature and clean copper inside the still is vital to allow various chemical reactions to take place, removing highly volatile sulphur compounds – chief among them dimethyl trisulphide or DMTS – and helping in the formation of esters, which tend to give the spirit a fruity character.
What im not sure about is exactly where the temperature of the ‘boil’ in the still has to be in order to ensure that these reactions take place.
Very interesting! I suppose it stands to reason that the stinky molecules associated with rotting food (mostly sulfur- and nitrogen-containing compounds) would be fairly volatile, and would bind fairly strongly to copper... My gut would have been to go with a glass fractionating column, but perhaps one could get the same effect merely by having an easily replaced copper wire or mesh insert...
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perhaps one could get the same effect merely by having an easily replaced copper wire or mesh insert...
Interesting thought. That would allow you to balance the mix between fruit and sulfur.
I know that some distillers using stainless steel refer to sacrificial copper, maybe that is what they are doing.
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So when will the moonshine be ready guys?
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So when will the moonshine be ready guys?
When you hear the singing ::)
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perhaps one could get the same effect merely by having an easily replaced copper wire or mesh insert...
Interesting thought. That would allow you to balance the mix between fruit and sulfur.
I know that some distillers using stainless steel refer to sacrificial copper, maybe that is what they are doing.
Yeah, I would classify the copper insert as "sacrificial."
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So when will the moonshine be ready guys?
Believe it or not, I would rather just buy the stuff. I don't drink enough for the cost to matter, I doubt I could produce high-enough quality booze if I tried, and distillation is one of the more annoying (and potentially dangerous) procedures I have to do in the lab (ie not my idea of fun)
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From wine to recreational inhalants. Slippery slope. :o
(major tangent, happy to split this off into another thread if people are interested):
Actually, I think alcohol is more similar (in terms of chemical, biochemical and metabolic profiles) to inhalants and anesthetics (other simple molecules, which have low binding affinities to several receptors) than to drugs like opiates or cocaine, or psychedelics (which are more complex molecules that specifically target and bind to one or two types of receptors)
This makes simple "solvent" drugs much more dangerous than their more complex counterparts for two major reasons:
(1) Much larger doses of non-specific drugs are required—doses of ethanol are measured in deciliters or ounces, while highly potent and specific drugs are usually counted in mg (sometimes even only µg). This will tax the metabolism substantially, and also makes straight-up chemical toxicity more problematic (nobody ever got liver poisoning from lsd). I believe that the intoxicating effects of both methyl alcohol and allyl alcohol are probably quite similar to those of ethanol, but both are metabolized to fantastically toxic compounds: methyl alcohol is metabolized to the highly toxic formaldehyde and formic acid, as alluded to in the OP, while allyl alcohol becomes highly electrophilic acrolein and acrylic acid.
(2) There is no antidote for a non-specific drug. If someone ODs on morphine, Naloxone can reverse it; if someone ODs on diazepam, flumazenil can reverse it. If someone ODs on ethanol (or toluene)... you basically just have to give life support and try to flush their system, and hope they recover. (This second point is somewhat of an oversimplification, but you get the idea...)
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(major tangent, happy to split this off into another thread if people are interested):
Actually, I think alcohol is more similar (in terms of chemical, biochemical and metabolic profiles) to inhalants and anesthetics (other simple molecules, which have low binding affinities to several receptors) than to drugs like opiates or cocaine, or psychedelics (which are more complex molecules that specifically target and bind to one or two types of receptors)
Thanks for this really interesting view. Not such a major tangent considering the OP and safety, because i would read your post alongside your comment:
So when will the moonshine be ready guys?
Believe it or not, I would rather just buy the stuff........
I have the same attitude, i’d rather buy taste than hit. However, there is a section of the winemaking/moonshine club which is in it for cheap alcohol and prepared to sacrifice taste and they are in danger from the issues you raised.
Having said that, some homemade wines are very good. I used to do quite a bit but now just make mead as we often have a surplus of unripe honey - just putting 7kg into the tub at the moment.
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Brewing beer teaches you so much science. It is far more complex than distilling or wine making.
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Brewing beer teaches you so much science. It is far more complex than distilling or wine making.
I agree brewing can teach science - if prople allow it to - but i dont find it more complex than distilling or winemaking.
Where do you see the added complexity occuring?