Understanding Heads
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Understanding Heads
Hi Everyone!
I posed this question in the welcome thread and was advised to put it here:
My goal is to get good at eau de vie and I still have some learning to do. I am guilty of using added sugar. But, the sugar bite is not my main concern. It is the excessive amount of heads and I don't want to go through the expense and effort to do an all fruit w/o sugar before understanding what's going on.
So, this is where I'm at:
At first, I thought that I got more heads with fruit than with All Bran because fruit has more methanol and methanol has a lower boiling point than ethanol so the methanol should be in the heads. I'm now convinced this is wrong.
According to: http://ec.europa.eu/research/agricultur ... _fruit.pdf" onclick="window.open(this.href);return false;" rel="nofollow , it is true that methanol boils lower than ethanol. But, methanol is more polar than ethanol and thus sticks to water much more than ethanol. As a result, the methanol to ethanol ratio is actually highest in the tails. (They present lots of data in this paper.) Paulinka also gives a good discussion of methanol and heads here: http://homedistiller.org/forum/viewtopi ... 38&t=54425 . The conclusion seems to be that methanol is a red herring. Everyone makes a big fuss about it. But, it is not the issue.
So, why do I get so much heads with fruit? If it was an issue with my equipment or hygiene or similar, why is my All Bran turning out fine? Also, it is well known that fruit makes more heads and especially high pectin fruits, such as apple. There must be a connection between the pectin/methanol and the heads, even if it is not as simple as what I originally thought. Are the components in the heads a product of pectin/methanol? What can we do to minimize the formation of this product?
Cheers!
White
I posed this question in the welcome thread and was advised to put it here:
My goal is to get good at eau de vie and I still have some learning to do. I am guilty of using added sugar. But, the sugar bite is not my main concern. It is the excessive amount of heads and I don't want to go through the expense and effort to do an all fruit w/o sugar before understanding what's going on.
So, this is where I'm at:
At first, I thought that I got more heads with fruit than with All Bran because fruit has more methanol and methanol has a lower boiling point than ethanol so the methanol should be in the heads. I'm now convinced this is wrong.
According to: http://ec.europa.eu/research/agricultur ... _fruit.pdf" onclick="window.open(this.href);return false;" rel="nofollow , it is true that methanol boils lower than ethanol. But, methanol is more polar than ethanol and thus sticks to water much more than ethanol. As a result, the methanol to ethanol ratio is actually highest in the tails. (They present lots of data in this paper.) Paulinka also gives a good discussion of methanol and heads here: http://homedistiller.org/forum/viewtopi ... 38&t=54425 . The conclusion seems to be that methanol is a red herring. Everyone makes a big fuss about it. But, it is not the issue.
So, why do I get so much heads with fruit? If it was an issue with my equipment or hygiene or similar, why is my All Bran turning out fine? Also, it is well known that fruit makes more heads and especially high pectin fruits, such as apple. There must be a connection between the pectin/methanol and the heads, even if it is not as simple as what I originally thought. Are the components in the heads a product of pectin/methanol? What can we do to minimize the formation of this product?
Cheers!
White
Re: Understanding Heads
You are correct it isn't the methanol that causes heads. The main compounds in heads are esters and the reason fruits give more heads is because esters are formed when heat is applied to solutions containing acids and alcohols. Fruits are naturally higher in acids than grains so it seems only natural that they would form more esters which means more heads.
They are not all "headsy" but I can't think of any way that we could, on a hobby level, seperate the "good" from the "bad".
They are not all "headsy" but I can't think of any way that we could, on a hobby level, seperate the "good" from the "bad".
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Re: Understanding Heads
I use to use pectinase to break down pectin to increase my yield slightly and clear my must. However I was told it will cause a slight elevation in the production of methanol and as i make brandy not wine haze reduction is of little importance to me. I don't think it significantly increased my yield to justify its use and although I understand the ratio of methanol to ethanol means it is not a serious issue I'd rather produce as little as possible so far this reason I just let the pectin be these days. The amount of methanol produced from fruit will be minuscule, the exception might be fermenting a pomace must (grappa) where too many sticks bark and bits of wood were left in the ferment
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- Danespirit
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Re: Understanding Heads
Heads are not just methanol but a blend of many different components, carrying over.
Some people belive if they tossed the foreshots, they are gone..this is not so.
The major part of them may be gone (depending on how carefull the distillation was) ..but some are still left.
Our nose and tongue are masterpieces of natures invention, because of this fact we can detect those unwanted chemicals in even tiny amounts.
Those fraction mingle with ethanol and cause what we call heads.
Now this fact stands true regardless of the still type. A fractionating column or a refluxstill just lowers the amount compared to a potstill.
Against some common assumtion the heads are NOT compressed in a refluxstill. For any gas to be compressed it needs a pressuredifferential, which we for gods sake try to avoid in a still, thus ventilating the top. What we can say, is the heads are concentrated in a column still..!
It makes good sense to keep the heads instead of tossing them, cause the major part of them is good ethanol we can recover in a feints run.
Some people belive if they tossed the foreshots, they are gone..this is not so.
The major part of them may be gone (depending on how carefull the distillation was) ..but some are still left.
Our nose and tongue are masterpieces of natures invention, because of this fact we can detect those unwanted chemicals in even tiny amounts.
Those fraction mingle with ethanol and cause what we call heads.
Now this fact stands true regardless of the still type. A fractionating column or a refluxstill just lowers the amount compared to a potstill.
Against some common assumtion the heads are NOT compressed in a refluxstill. For any gas to be compressed it needs a pressuredifferential, which we for gods sake try to avoid in a still, thus ventilating the top. What we can say, is the heads are concentrated in a column still..!
It makes good sense to keep the heads instead of tossing them, cause the major part of them is good ethanol we can recover in a feints run.
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Re: Understanding Heads
Pretty sure you are missing the context in which the term compressed is used in relation to fractioning, they are concentrated and therefore by description compressed . The term has more than one meaningDanespirit wrote:Against some common assumtion the heads are NOT compressed in a refluxstill.
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Re: Understanding Heads
Danespirit, that batch of Blackberry Shine seemed to be ALL heads till I got to the last jar. It is still sitting in the shed, and I haven't decided what to do with it. I may dilute it and rerun it, but I may be wasting more propane.....it does have a lot of ethanol in it.
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Re: Understanding Heads
Thanks for the response. I have been starting with fruit wine recipes and turning down the sugar and acid blend. Probably should completely eliminate the acid blend, then.Bagasso wrote:You are correct it isn't the methanol that causes heads. The main compounds in heads are esters and the reason fruits give more heads is because esters are formed when heat is applied to solutions containing acids and alcohols. Fruits are naturally higher in acids than grains so it seems only natural that they would form more esters which means more heads.
They are not all "headsy" but I can't think of any way that we could, on a hobby level, seperate the "good" from the "bad".
Next run, I'll go for low acid and low abv to reduce both the yeast puking and the ester formation.
Re: Understanding Heads
Fruits also contain more natural methanol which come off first along the the esters and other higher volatiles.Bagasso wrote:You are correct it isn't the methanol that causes heads. The main compounds in heads are esters and the reason fruits give more heads is because esters are formed when heat is applied to solutions containing acids and alcohols. Fruits are naturally higher in acids than grains so it seems only natural that they would form more esters which means more heads.
They are not all "headsy" but I can't think of any way that we could, on a hobby level, seperate the "good" from the "bad".
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Re: Understanding Heads
From what I have been reading, at the concentrations we are talking about, methanol has a pleasant sweet taste that is essential to the character of eau de vie. Using pectinase on a hazy must probably neither changes the yield or methanol content significantly. It becomes more important when you ferment a pulp.thecroweater wrote:I use to use pectinase to break down pectin to increase my yield slightly and clear my must. However I was told it will cause a slight elevation in the production of methanol and as i make brandy not wine haze reduction is of little importance to me. I don't think it significantly increased my yield to justify its use and although I understand the ratio of methanol to ethanol means it is not a serious issue I'd rather produce as little as possible so far this reason I just let the pectin be these days. The amount of methanol produced from fruit will be minuscule, the exception might be fermenting a pomace must (grappa) where too many sticks bark and bits of wood were left in the ferment
The stuff I'm tasting is definitely not pleasant and sweet. (i.e. not methanol). It could be esters, as Bagasso suggested. But, I'm also not discounting that it is a methanol metabolite produced by yeast under stress. In humans, methanol metabolises into formaldehyde and formic acid (the stuff that ants give off). Why not in yeast?
Re: Understanding Heads
True but, is methanol "headsy"? It is said to have a sweet smell and tastes similar to ethanol so it doesn't sound like it to me.Bushman wrote:Fruits also contain more natural methanol which come off first along the the esters and other higher volatiles.
Now, since gov's all over the world use methanol to scare people away from stilling it has become the label of all the "bad stuff" that can come out of a still.
Last edited by Bagasso on Tue May 19, 2015 9:40 am, edited 1 time in total.
Re: Understanding Heads
Have you seen this thread http://homedistiller.org/forum/viewtopi ... =1&t=12350?WhiteLikker wrote:The stuff I'm tasting is definitely not pleasant and sweet. (i.e. not methanol). It could be esters, as Bagasso suggested. But, I'm also not discounting that it is a methanol metabolite produced by yeast under stress. In humans, methanol metabolises into formaldehyde and formic acid (the stuff that ants give off). Why not in yeast?
Look at the difference in ethyl acetate between the fores and the final product tested.
ETA: You will also notice that plain sugar washes produce almost no methanol but, there is always heads in there.
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Re: Understanding Heads
Pure methanol, is tasteless and clear.The stuff I'm tasting is definitely not pleasant and sweet. (i.e. not methanol). It could be esters, as Bagasso suggested. But, I'm also not discounting that it is a methanol metabolite produced by yeast under stress. In humans, methanol metabolises into formaldehyde and formic acid (the stuff that ants give off). Why not in yeast?
White Likker..you are correct about how methanol acts on the human body.
Ironicly the cure for methanol poisoning is...lots of ethanol.
This would keep the liver busy breaking down the ethanol, slowing the breakdown from methanol to formic acid and formaldehyde.
Yeast is eukariotic, so is the human body.
The difference however is that yeast is unicellular and therefore acts very divergent from the human body or for that sake animals.
Our metabolism is far more complicated than that from a simple yeast cell.
Yeast cells can tolerate a lot more "punishment" than cells in our body...still nature has it's limitations.
Yes, Appalachia-Shiner ..i would definatly try to recover it..would be a shame to let it go down the drain..Danespirit, that batch of Blackberry Shine seemed to be ALL heads till I got to the last jar. It is still sitting in the shed, and I haven't decided what to do with it. I may dilute it and rerun it, but I may be wasting more propane.....it does have a lot of ethanol in it.
Ok, Crow..you win on that compression thing..hey..let's compress the hell out of those heads..the sooner they are gone..Pretty sure you are missing the context in which the term compressed is used in relation to fractioning, they are concentrated and therefore by description compressed . The term has more than one meaning
Re: Understanding Heads
The compounds which cause you to detect heads are mostly aldehydes, diacetyl, etc
Methanol is present, as is shown in the link, all throughout the run. Some of it is rendered inert of negative effects to health during aging due to the complexes it forms with other organic compounds.
The best way to avoid methanol is to press juice from fresh fruit. Before it begins to ferment, cool it down to very low temperatures, filter with powerful agents (diatomaceous earth) and rack off before fermentation. This won't completely get rid of methanol, it will reduce it though.
Methanol actually not created by fermentation; methanol is responsible for holding together pectin molecules in many plants and is simply freed as microorganisms break it down.
Methanol is present, as is shown in the link, all throughout the run. Some of it is rendered inert of negative effects to health during aging due to the complexes it forms with other organic compounds.
The best way to avoid methanol is to press juice from fresh fruit. Before it begins to ferment, cool it down to very low temperatures, filter with powerful agents (diatomaceous earth) and rack off before fermentation. This won't completely get rid of methanol, it will reduce it though.
Methanol actually not created by fermentation; methanol is responsible for holding together pectin molecules in many plants and is simply freed as microorganisms break it down.
The still is not a liar. Mash and ferment quality is 99.9% of your performance.
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Re: Understanding Heads
No doubt, ethyl acetate is an important component of fores/heads. But, are the big and nasty heads that I'm seeing in my sugared up apple wash really just because more acid makes more ethyl acetate and that's it? If that's the case, a sugar wash with lots of acid (added lemon juice or acid blend) should also produce big bad heads. That would be an interesting experiment that could eliminate methanol (or its products) as a culprit in heads. Has anyone done that?Bagasso wrote: Look at the difference in ethyl acetate between the fores and the final product tested.
ETA: You will also notice that plain sugar washes produce almost no methanol but, there is always heads in there.
Re: Understanding Heads
No, a specific acid (acetic acid) and ethanol give you ethyl acetate. Other acid/alcohol combinations will give other esters which may or may not be "headsy".WhiteLikker wrote:No doubt, ethyl acetate is an important component of fores/heads. But, are the big and nasty heads that I'm seeing in my sugared up apple wash really just because more acid makes more ethyl acetate and that's it? If that's the case, a sugar wash with lots of acid (added lemon juice or acid blend) should also produce big bad heads.
That is what the link shows. Both the fores (which was really a fores/heads cut) and the "filtered and diluted" cut had "less than 5mg/l" (trace amounts) of methanol. In comparison fresh OJ is supposed to have more than 30mg/l and store bought juice is supposed to have an average of 140 mg/l and neither smell or taste like heads.That would be an interesting experiment that could eliminate methanol (or its products) as a culprit in heads. Has anyone done that?
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Re: Understanding Heads
Acetic acid comes from ethanol and a fruit wash wouldn't have any more than a sugar wash. So, the culprit must be one of the acids present in fruit (citric, malic, tartaric...). Your link also shows a nice cut off with ethyl acetate very much concentrated in the first 100 ml. In some fruit washes, the off flavours in the heads seem to not get cut off so nicely.Bagasso wrote: No, a specific acid (acetic acid) and ethanol give you ethyl acetate. Other acid/alcohol combinations will give other esters which may or may not be "headsy".
Re: Understanding Heads
Actually, during fermentation, the main source would be acetobacter bacteria so, you can't really say how much acetic acid any given wash may have without testing for it specifically.WhiteLikker wrote:Acetic acid comes from ethanol and a fruit wash wouldn't have any more than a sugar wash. So, the culprit must be one of the acids present in fruit (citric, malic, tartaric...).
Now you are getting into the area of taste and that can't be sorted out over the internet. One man's "off flavor" can be another's "character" or "complexity".Your link also shows a nice cut off with ethyl acetate very much concentrated in the first 100 ml. In some fruit washes, the off flavours in the heads seem to not get cut off so nicely.
The main culprit in heads is ethyl acetate. There is no other hot solventy compound found in greater numbers. Add to that a 1ºC difference in boiling point temp from ethanol and that pretty much says it all.
That doesn't mean that there can't be other things that you feel are off flavors but that would vary greatly depending on the fruit, yeast, fermenting conditions and even how you run. You are not going to weed them out without a lab.
ETA: Also the test done in that thread was run through a 5L airstill which is why the heads cut was only 100ml and I don't know what you mean by clean cut off since their was still ethyl acetate in the finished product.
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Re: Understanding Heads
I think you might be over looking a few other culprits like amyl acetate, amyl ethanol,butyl E., Isobutyl E., acetaldehyde, isopropyl, propyl E., acetone, furfural, methyl alcohols and other methyl compounds. I'm sure I have missed a few but most of these will be in most heads as I understand, its why different head cuts (if made in small increments) taste and smell quite different from each other
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Re: Understanding Heads
Well, "main culprit" implies that there are others.thecroweater wrote:I think you might be over looking a few other culprits
Then you have those who end up blending a little late heads back in because their likker doesn't taste right without it. What happened to change those culprits into good guys?
Re: Understanding Heads
Would a healthy fermentation with plenty of yeast, at a low enough temperature, with enough time to clear up the diacetyl help the problem?
Re: Understanding Heads
I know it's a problem for beer but I'm not sure diacetyl is generaly a distillation problem. Some rum fans work hard to get butter and butterscotch flavors in their distillate.Cotron wrote:Would a healthy fermentation with plenty of yeast, at a low enough temperature, with enough time to clear up the diacetyl help the problem?
Re: Understanding Heads
Ethyl acetate is responsible for a number of things, but the smell of heads is not among it.
Heads get their harsh smell from the formation of aldehydes, ketones and trace amounts of volatile acid like acrylic.
In mashes where bacteria has been allowed to break down large acids into simple carboxylic acids, and also in combination with oak acids, a large amount of both higher alcohols and acids will convert to esters. Esters smell fruity; I have seen lots of anecdotes - even repeated in wikipedia - saying that ethyl acetate is responsible for the smell of heads, but having made the ester directly through reflux distillation I have never actually smelled it that way.
Heads get their harsh smell from the formation of aldehydes, ketones and trace amounts of volatile acid like acrylic.
In mashes where bacteria has been allowed to break down large acids into simple carboxylic acids, and also in combination with oak acids, a large amount of both higher alcohols and acids will convert to esters. Esters smell fruity; I have seen lots of anecdotes - even repeated in wikipedia - saying that ethyl acetate is responsible for the smell of heads, but having made the ester directly through reflux distillation I have never actually smelled it that way.
The still is not a liar. Mash and ferment quality is 99.9% of your performance.
Re: Understanding Heads
Interesting. How about the burn?MDH wrote:having made the ester directly through reflux distillation I have never actually smelled it that way.
By harsh do you mean the volatiles that seem to air out when left open a while or the ones that remain after that?
Just trying to point out that there is a difference.
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Re: Understanding Heads
I'm mainly interested in the difference between heads from a sugar wash and from fruit. The heads from a sugar wash are easy to handle.Bagasso wrote:Actually, during fermentation, the main source would be acetobacter bacteria so, you can't really say how much acetic acid any given wash may have without testing for it specifically.
...
The main culprit in heads is ethyl acetate. There is no other hot solventy compound found in greater numbers. Add to that a 1ºC difference in boiling point temp from ethanol and that pretty much says it all.
That doesn't mean that there can't be other things that you feel are off flavors but that would vary greatly depending on the fruit, yeast, fermenting conditions and even how you run. You are not going to weed them out without a lab.
In general, esters with more carbon carry over later. Also, the more carbon in the acid, the more carbon in the ester. Acetic acid only has 2C and it's ester, ethyl acetate, has 4. So, ethyl acetate comes out early. Malic and tartaric acids have 4C and citric acid and vitamin C have 6C. Maybe that's why no one distils fermented citrus. The esters will be in with the hearts. Many berries are also high in citric acid.
The stuff that is usually used for brandy (grapes, apples, plums...) is mainly malic and tartaric and I would expect these esters to come out after ethyl acetate, but still manageable.
In my latest attempt at fruit brandy, I used store bought apple juice, with a ton of vitamin C added. My guess is that the apple juice by itself (malic acid) would have been fine and that the added vitamin C is producing esters that are running into the hearts.
The esterification equilibrium has alcohol and acid on one side and ester and water on the other. That means you get way more esters if you push the abv. (Guilty as charged.)
Disclaimer: I am not an expert in this. The above is the result of a bit of reading with some guesses at conclusions. It should be taken as food for thought, rather than as fact.
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Re: Understanding Heads
That's interesting. The harsh biting off taste in my fruit distillate is very difficult to mask, even with strong commercial flavorings. But, if I throw in a slice of ginger and a star anise, the off taste seems to get neutralized, rather than masked. Is this the same process?MDH wrote: in combination with oak acids, a large amount of both higher alcohols and acids will convert to esters. Esters smell fruity;
[And, yes, the offending taste is more like an acid than an ester.]
Re: Understanding Heads
There are few qualified experts on here. All most of us can do is look things up and share what we find.WhiteLikker wrote:I'm mainly interested in the difference between heads from a sugar wash and from fruit. The heads from a sugar wash are easy to handle.
Esters are not necesarily bad. They are part of the flavors that distillers are after.In general, esters with more carbon carry over later. Also, the more carbon in the acid, the more carbon in the ester. Acetic acid only has 2C and it's ester, ethyl acetate, has 4. So, ethyl acetate comes out early. Malic and tartaric acids have 4C and citric acid and vitamin C have 6C. Maybe that's why no one distils fermented citrus. The esters will be in with the hearts. Many berries are also high in citric acid.
What I found is that vitamin C (ascorbic acid), despite the name, is not an acid but a lactone.In my latest attempt at fruit brandy, I used store bought apple juice, with a ton of vitamin C added. My guess is that the apple juice by itself (malic acid) would have been fine and that the added vitamin C is producing esters that are running into the hearts.
I think you are looking at it the wrong way. There are more than enough alcohols even in low abv washes. Only a tiny amount become esters.The esterification equilibrium has alcohol and acid on one side and ester and water on the other. That means you get way more esters if you push the abv. (Guilty as charged.)
Pushing the abv will increase esters and also other congeners but that is because the yeast is stressed. Either way it's a bad start and any chemical reactions taking place only makes things worse.
Re: Understanding Heads
These acids, and their esters, are far too heavy and not volatile enough to make it through distillation. Bacteria can metabolize them into other compounds and those will make it through distillation. Citric acid is metabolized by some strains of lactobacillus into diacetyl, which is the fake popcorn smell.WhiteLikker wrote:The stuff that is usually used for brandy (grapes, apples, plums...) is mainly malic and tartaric and I would expect these esters to come out after ethyl acetate, but still manageable.
The still is not a liar. Mash and ferment quality is 99.9% of your performance.
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Re: Understanding Heads
According to the link in the first post of this thread, the solubility of esters depends very much on the alcohol content and they can be transferred into the distillate as long as the alcohol content in the steam phase is high. As an example, isoamylacetate, with a boiling point of 142 °C, is carried over much earlier than methanol.MDH wrote:These acids, and their esters, are far too heavy and not volatile enough to make it through distillation. Bacteria can metabolize them into other compounds and those will make it through distillation. Citric acid is metabolized by some strains of lactobacillus into diacetyl, which is the fake popcorn smell.WhiteLikker wrote:The stuff that is usually used for brandy (grapes, apples, plums...) is mainly malic and tartaric and I would expect these esters to come out after ethyl acetate, but still manageable.
Re: Understanding Heads
WhiteLikker,
although I get what you are trying to figure out, I think at some point the most practical answer is "You get what you get".
Sugar wash gives you X amount of heads and the fruit wash gives you 2X the amount of heads then, that's what you get.
The study you posted has a bunch of good information but you have to remember that they went into the study with the same idea that most have, "methanol is concentrated in the fores" and "methanol is the reason behind bad distillates". They found out different and despite having a lot of good info and it being backed by actual lab results they don't really offer any tips on reducing heads.
although I get what you are trying to figure out, I think at some point the most practical answer is "You get what you get".
Sugar wash gives you X amount of heads and the fruit wash gives you 2X the amount of heads then, that's what you get.
The study you posted has a bunch of good information but you have to remember that they went into the study with the same idea that most have, "methanol is concentrated in the fores" and "methanol is the reason behind bad distillates". They found out different and despite having a lot of good info and it being backed by actual lab results they don't really offer any tips on reducing heads.
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Re: Understanding Heads
The study was trying to reduce methanol for regulatory compliance, not to reduce heads. The EU says you're allowed x mg/L and that's it.Bagasso wrote:The study you posted has a bunch of good information but you have to remember that they went into the study with the same idea that most have, "methanol is concentrated in the fores" and "methanol is the reason behind bad distillates". They found out different and despite having a lot of good info and it being backed by actual lab results they don't really offer any tips on reducing heads.
Personally, I don't care about methanol. I don't even really care about heads in general but rather some really harsh tastes that seem to come with the heads in some of my fruit washes.
If you start off with wrong models, perfectly logical conclusions lead to a bad product. If you think heads = methanol then the logical conclusion would be to add sugar to your fruit washes.
The study was the first thing I ever read that was even close to a scientific treatment of distillation. Between that and the discussion in this thread my understanding of distillation has changed considerably:
1) Methanol does not come out with the fores or heads. Once methanol is mixed with ethanol it is difficult to separate them. That's why the government uses methanol to poison industrial alcohol. It wouldn't work if you could just boil it off.
2) We focus way too much on boiling points when we try to predict what comes over when. It's much more complicated than that. It depends on what sticks to what and what is soluble in what etc.
3) Some heavy, non-volatile, high boiling point (and maybe nasty) substances can make it into the distillate but, only as long as the alcohol concentration is high. Once the alcohol concentration drops below a certain point, those nasties can't carry over any more and stay in the pot.
The last point explains a bunch of stuff that never made sense to me before. For example, the practice of throwing previous heads in with the next run. If you don't get rid of any of the heads, you'd expect them to just accumulate with each run. But, what actually happens is that only a limited amount of nasties can get carried over in each run and the rest stay in the pot and get tossed out. And, the lower abv of the mash, the less nasties can get into the distillate.
So: don't worry about methanol, keep abv low, make generous cuts and throw the heads and tails in with the next run.