>I recently read a recipe for corn mash in which the author commented
>that you must stop the fermentation at the right point or the alcohol
>would be wood alcohol rather than ethanol.
>Is there any validity to that, or was he just completely off base? I
>would think that the amount of ethanol and methanol produced would be
>a factor of the ingredients and not the duration of fermentation
From what I understand of the process, he was wrong.
(David...please correct me where I go astray from here ...)
The yeast act on the simple sugars present (the glucose) to convert them to
I believe that it is the presence of other methyl compounds in the wash
(say coming from pectin or husks etc) that get converted to methanol. The
way to minimise this is to try and avoid have non-fermenatbles there in the
first place (eg remove the grape stalks, etc), or the simplest of just
starting with sugar, water, and nutrients only.
About the only bit I still have some doubt on, is what happens when the
yeast gets stressed, eg if the temperatures get too hot, or run out of
nutrients ... at this point they can start producing some compounds other
than ethanol - eg the cogeners of propanol & butanol.
I think this was explained at AllTechs
But i don't believe that methanol is produced.
>I think I know the answer to this... but what happens to the methanol
>produced in beer and wine making? Is it consumed... but in harmless
Yes - its the dilution that helps. A 20L wash of beer would take a while
for you to get through, but if double distilled down to 1 bottle of
spirits, it could be attempted by some over the course of a single evening
(not that much would be recounted after !). The distilling has
concentrated it up to far higher levels than originally present.
>My reason for curiosity is as a homebrewer.... is there a danger of
>creating dangerous levels of methanol if fermentation is allowed to
My believe is no. Many washes are fermented, then left to sit around for a
week or two before distilling. Beers in particular are left to ferment for
months without harm. But do cover the simple stuff as best you can - don't
stress the yeast with high temperatures, do provide enough nutrients to
help them out, have the wort nicely aerated when you pitch the yeast, and
keep any crap out of the wash that doesn't need to be there.