Long fermentation = off flavours?

[Ethan]

Hi

Ive got 45L of wash going at the moment. 2:1 sugar/molasses with a nice low pH. The last few batches Ive done I have let go until they have comletely stopped bubbling - about 2 weeks. I let it go this far to avoid foaming in the boiler and sugar burning on my internal element. It seems to have worked in that respect.

I have read a few things that suggest that any fermentation over 72 hours will start to produce off flavours? I double pot distill to around 80% abv and stop collecting very early on the second run; around 92C. It doesn't seem too bad. My wife likes the un-aged white dog, and I don't mind it either. It gets a lot better after a few months in glass with chunks of charred white oak.

Should I stop the fermentation earlier for better results?

[Guest]

nice slow LONG ferments will make better results with no off flavours(from my experience) and will allow the yeast to tolerate a higher alcohol percent

[DBM]

Ethan;
I like for my mash to finish fermenting before I run it. If you want it to finish quicker try puting it in a warmer place.
Because of timing I need to run mine ever seventh day. I have found that my corn and backset sourmash will be ready if I keep it in a place with a temp of 70 + deg. (furnace room). In the spring of the year when I move the fermenting outside and the days are 80 + and low 60's at night it will take off, then when the temp drops to 40's at night you can see it slow down. The taste of the whiskey pretty much stays the same though.
The few times that I ran a wash that I felt needed to ferment for another day or two, I didn't notice any difference in the taste of the whiskey. I did notice that the wash really tookoff when the backset cooled though, must have been the sugar still in the wash.

[John Q.]

I put my wife's heating pad under the fermenter; it's kind of a mini electric blanket. It has a thermostat and keeps the temp consistant.

[ricki]

One thing to beware if you let it go too long is the build up of acetaldehyde, which is a normal part of the yeast biochem pathway and if they are put into a stressed/starved situation will produce a lot more of it, but depending on the yeast, you might be fine.
My understanding about the 72 hour ferment has to do with grain mashes--if you let it go too long, a secondary fermentation from lactic acid bacteria will begin to take over. Some distilleries actually allow this to happen to an extent to add certain flavors to the whiskey

[booger]

The last few batches Ive done I have let go until they have comletely stopped bubbling - about 2 weeks.

Just don't let it sit on a yeast "cake" after it has finished fermenting...what happens then is called yeast autolysis (sp?) and it causes the wet cardboard taste. Letting it ferment out slowly, as long as it is an active fermentation, is never a bad thing. My understanding of the biology of it is that there is less likelihood of a sever mutation in the yeast as it reproduces resulting in a "truer" flavor.