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Jun 08, 2022 View:

Acetic Acid produced

I distilled a batch of rye today that appears to contain a lot of acetic acid!

The normal fermentation was pretty well complete 3 days ago but because of other commitments I left it (have left many batches this long before)

The temperature in the fermenter was initially 27 c (80 f) then gradually dropped to 15 c (59 f) which is usual

Last night the temperature was back up to 25 c (77) Ambient temp about 12 c (54 f)

I ran it into the still last night and heated to 60 c (140 f) to pasturise it becuse I assume it had started some type of secondary fermentation.

When I ran the stripping run today (Alembic still, no plates) the tails had a VERY distinct vinegar taste. The low wines do as well but not so obvious.

Hydrometer indicates the alcohol yield is way down as well.

I assume I have got a wild acetobacter infection in the fermenter.

Is this very common?

Is it very hard to get rid of ? I usually use a CIP spray and dairy sanitiser.

Thanks in advance for any help



This is one reason to run a sour mash. Use stillage to ferment around 4 ph. It will just about make your mash bullet proof.


Fldme, on a rye how much stillage per 100 gallons to make this "bullet proof"?


Fldme, on a rye how much stillage per 100 gallons to make this "bullet proof"?


Hey Pete,

Given that the mash sat for longer than normal it's not surprising that the Acetobacter took hold. The fact that you haven't had an issue in the past may be a matter of luck as much as anything else. Acetobacter is aerobic so as the fermenter settles down and the CO2 stops evolving out of the wash you start to get O2 coming in contact with the surface of the wash and that's when those little guys take hold. If you're using open fermenters, I think you are from previous posts, you may want to put a CO2 blanket on top if you aren't going to be able to strip it right away, you could also fab a floating lid or tank lid for your fermenter that you use when it's going to need to sit for a while. Certainly sour mashing could help, you need to get below pH 4.5 to inhibit Acetobacter, but if that's not part of your current process I wouldn't think you'd want to introduce that and change your flavor profile.


You add nothing and come in at 4. I would stil add backset, it will provide a buffer, holding the ph. Good clean backset is not really too acidic. A good rule of thumbe of 30 percent backset. Screened of all solids is the best.


Acidulated malt is a good way, too.

Whenever I have to leave a fermentation a little longer than necessary, I count my blessings for jacketed tanks. Not much likes to grow below 40 degrees.


Acidulated malt wil drop the ph, it you miss out on the other good stuff from using backset. Maine thing being nutrients. Foam control and continuity from batch to batch.