Something of a chemistry question

[Fireflower]

Hello all, and thanks for this interesting forum! I have a bit of a skull scratcher that I hope someone can help me with.
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Question – does rapid fermentation (or higher than advised fermentation temperature) lead to overproduction of methanol?

I have run into this twice now and it puzzles me. I had a batch of banana that I distilled (laboratory quantities &amp; methodology for analysis only) and it tested out at 70% methanol! Nasty nasty. Now I have a raspberry that is in all other respects a beautiful wine – deep red color, clear, big body, HUGE flavor and a nose you could use for air freshener! However, it finishes with a positively astringent character, almost like you drank something hydroscopic; acetone maybe. It dries your tissues! You want to drink water after you sip it. I think I’ve got the big methanol problem again… I’m going to borrow a distillation tube and check this batch too.

Both wines fermented frumiously to about 19% Alcohol in just three days on 71B1122, averaging 72degrees throughout. I’m guessing this was the cause, but I don’t know for sure. Any ideas?

Thanks in advance,
Marc

 

[Wade E]

What size were these batches as 1-3 gallon batches will ferment a lot faster. What was starting sg and finish sg at 3rd day. Ive had fast fermentation like that on smaller batches but never a 5-6 gallin batch and never had a problem with it.ny other ingredients in these batches like nutrient and energizer or sugar. Any little bit of info can help hopefully solve your problem.

 

[masta]

Welcome Marc,
From what I have read, fermenting grains or fruit high in pectin (such as bananas) can produce a very, very small amount of methanol in addition to the ethanol. In addition a high fermentation temp (72 degrees isn't high), using pectin enzymes, and high %abv could produce higher levels of methanol.


If your testing of a sample truly showed a level of 70% methanol if would have to come from the very first part of the distillation since methanol comes off before the ethanol.


Some levels of methanol in distilled spirits and other liquids we consume:


<UL>
<LI>Home distilled spirit (untreated): methanol 0.0067%, ethanol 99.632%, fusils 0.361%
<LI>Commercial vodka: methanol 0.013%, ethanol 99.507%, fusils 0.48%
<LI>Poor quality home distilled spirit : methanol 0.0186%, ethanol 98.453%, and fusils 1.528%</LI>[/list]


Methanol is commonly encountered in the diet. The table below shows the amount of methanol you would get from a can of diet soft drink, along with amounts found in the same volume of several fruit juices. Methanol is well known to be poisonous in large quantity. "Large quantity" means tens or hundreds of grams. Your liver can deal with reasonable quantities of methanol, metabolizing it so that it can be excreted. If you start drinking enough methanol to get inebriated, you overwhelm your liver's metabolic machinery, and serious problems result.




<TABLE cellSpacing=2 cellPadding=0 width=450 border=1><T>
<T>
<TR>
<TD width="50%">Diet soft drink (12 oz can)</TD>
<TD width="50%">0.024 gram</TD></TR>
<TR>
<TD width="50%">Orange juice</TD>
<TD width="50%">0.018 gram</TD></TR>
<TR>
<TD width="50%">Apple juice</TD>
<TD width="50%">0.021 gram</TD></TR>
<TR>
<TD width="50%">Grape juice</TD>
<TD width="50%">0.046 gram</TD></TR>
<TR>
<TD width="50%">Tomato juice</TD>
<TD width="50%">0.085 gram</TD></TR></T></T></TABLE>Edited by: masta

 

[Fireflower]

Thanks All,
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I did some prowling around on the net yesterday and found the answer. You’re right, Masta, pectin is the source. Specifically, methanol is produced by the enzymatic hydrolysis of the pectins present in the fruit and any pectinase you add as a juice extractant. Yeast don’t make methanol – news to me.

Further, higher temps can increase the rate of reaction, leading to more methanol.

Both of these batches were kind of experimental; I was trying to see if there was an upper bound on how much fruit I could use in a wine without ruining it in some way… these batches were on the order of 5lbs / gallon, starting SG ~1.1. They were fermented on the skins (both banana &amp; raspberry) &amp; used pectic enzyme prior to fermentation. The Banana was a 3gallon batch, the raspberry 4.5. Both used 1122 and the primary was a 10 gallon plastic Rubbermaid bucket.

The distillate results were correct; ~20% total alcohol with 70% methyl / 30% ethyl for the banana. I’m a geek; this was lab grade work. Careful temperature monitoring (methanol &amp; ethanol have different boiling temps) yields the lighter alcohol (methanol) first. I was stunned. Can you imagine the hangover you’d have from a bottle of this stuff? I can’t wait to wander over to the chem. lab &amp; run this again on a small quantity of the raspberry. Judging from the finish, it may be higher… (The banana, BTW, was just <I style="mso-bidi-font-style: normal">awful[/I]. The raspberry, on the other hand, is exactly what I wanted in all respects except for the mouth drying finish!)

If the raspberry is high methanol, I’m going to try this wine again using a steamer juicer on the fruit (and no pectic enzyme, obviously). Plus, a temperature control system could be cobbled together as well using some bits &amp; pieces from around my shop.

Has anyone else produced a wine with this characteristic ‘astringency’ on finish? Is this at all a common problem for other hobbyists?

Thanks again for your help.
Marc

 

[rgecaprock]

W E L C O M E T O T H E F O R U M, M A R C !!!
It is good to have you here.


Ramona

 

[masta]

More Info found on the web:
Methanol very toxic by ingestion or even inhalation and causes blindness and death. A level of 0.2% in the air is the safe maximum when it is being inhaled. A lethal swallowing dose is 50 ml to 100ml. Max safe level in liquids for consumption is 4% by volume which is 31650 mg/liter or 31650 ppm. Methanol occurs in many fruits at level of 50 ppm eg apple juice contains 50 ppm. However a few are quite high eg gooseberries can have levels of 3000 ppm. Of interest is the levels in alcoholic drinks where it can occur at levels of 0.1% or 790 mg/liter especially brandies and red wines. In the USA the max permissible by law is 0.35% which is 2765 ppm. So how does it arise ? From the yeast or an enzyme in the grape?


Evidence suggests the latter:


1 red wines contain more ME than white wines
2 adding commercial pectinase increases ME concentration


3 heating increases ME concentration


Methanol present in these beverages arises from action of the enzyme pectin esterase (PE) on the pectin from the grapes during the mashing stage. In the production of red wine the grape skins are retained in the mash and in white wine the skins are removed: the skin is the main source of pectin. On average red wine contains about 200 ppm ME while white wine contains about 50 ppm. The esterase hydrolysis the releasing methanol.


Remedy hot pressing 85°C for 15 mins substantially reduces the level of PE and consequently the level on ME, but is expensive in terms of energy and has an effect on taste. Easier is vacuum distillation which reduces the alcohol concentration but this can be replaced. An enzyme-based system of removal using methanol oxidase/peroxidase/catalase has been successful.



I am not doubting your testing ability but I really have trouble with the numbers. If you used Lalvin 71B-1122 I am not sure you could ever get to 20% abv since the manufacturer states the abv tolerance of this yeast is only 14% and 20% abv would be almost 45% higher!






Many folks make fruit wines including banana and to have a level even remotely close to 70% methanol from fermentation would cause some serious issues. I do believe if this could happen it would have by now and hopefully reported to warn others. From my limited research on this all deaths or serous illnessfrom drinking fermented or distilled beverages isfrom drinking way too much in a short period of time or methanol spiked beverages.


If your banana wine is 20% abv and 70% is methanol not ethanol then drinking just1/2 of a 750ml bottle (~2 glasses) could kill you based on a lethal dose of &gt;50 ml.



Edited by: masta

 

[Fireflower]

Thanks, Ramona!
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I’m mystified, Masta, but not by the numbers. Yes, 1122 should die off long before you’d get to 20%, but if the bulk of the methanol production takes place *post* fermentation, then the yeasts wouldn’t have to generate more than the percentage of ethanol they could tolerate, leaving the esterase hydrolysis to account for the methanol and the high final abv.

This is only an hypothesis; I’m no organic chemist. My eth/meth ratios were rough estimates (+/- 2%?) based on the volume of liquids obtained. I wish I had saved some of this nasty brew! Trust me, there was no risk of anyone drinking it… I can’t wait to get into my friends chem. lab and test the raspberry now. That probably won’t happen till next week sometime (work gets in the way).

What concerns me more than the ratios is your statement that no one (to your knowledge) has reported this ‘phenomenon’ before. That’s troubling. If the raspberry has the same problem I’ll have plenty to experiment with and I take careful notes when making wine. I should be able to get to the bottom of it.

Thanks again for your help.

It’s peach time here in <?amespace prefix = st1 ns = "urnchemas-microsoft-comfficearttags" /><st1:State><st1lace>Colorado</st1lace></st1:State>, and my peach wine has yet to kill anyone! (or even make them wear glasses…;-)

Marc