Home Distiller

To say the least I'm a bit confused.

I just finished a stripping run of 20 L of Buccaneer Bob's rum. Life made me deviate somewhat on the fermenting vs distilling schedule. Meaning it has sat a couple months fermented out on the yeast. First impression of the fermented wash was quite sharp. Quickly moving on I stripped it out yesterday....and the numbers (and flavor) made no sense.

Disclaimer. I'm a retired chemist. I get distilling. I also have 12-18 distillations under my belt (mostly gin and scotch style whisky) and I've vetted my system and process. It all works text book.

That said, the product was very....vinegar like. Not quite, but close. And using the search feature I see that isn't terribly uncommon. But.

My product started coming off fine at about 80 C, I pulled my foreshots, and continued on. The first oddity is that the % coming off per my Tralle Hydrometer said 25% and proceeded to go down from there. By the time I had collected about 6 L of product the hydrometer said 5% but my still thermometer never went above 90C.

I verified both thermometer calibration with boiling water and a 2nd thermometer and the hydrometer with some previous 45% ABV I have age. They all checked out (clearly or I would not be writing).

Any thoughts anyone? I'm left with WTF!

I fear your ferment was infected with vinegar. That consumed the alcohol in the two months your was sat there, and so you had a very low alcohol content when you started distilling.

Try a different Proof & Traille hydrometer. I wonder if the calibration paper inside yours may have moved.

Running rum through a potstill should start your collection in the 55-60%ABV range with a ferment potential between 5-10%ABV. I doubt that the ferment got spoiled by a vinegar mother (which could reduce the alcohol content), although you did say it smelled somewhat like vinegar. I'm optimistic that you did get some alcohol from the ferment.

As a check of your P&T hydro, check it against a known product, store bought or home produced. If it proves correct, then you may be the victim of the vinegar bug. Hope not, but....
ss

edit - posted with grizzo.

I thought of that and held out hope given others commenting on a semi-vinegar taste. Know anyway to test that out?

Would that match the temp vs density mismatch?

Alchemist wrote:...Would that match the temp vs density mismatch?

Yep.

still_stirrin wrote: As a check of your P&T hydro, check it against a known product, store bought or home produced. If it proves correct, then you may be the victim of the vinegar bug. Hope not, but....

I did this already and said so.

Yes. Perhaps a vinegar infection.
But...

Alchemist wrote:My product started coming off fine at about 80 C, I pulled my foreshots, and continued on. The first oddity is that the % coming off per my Tralle Hydrometer said 25% and proceeded to go down from there. By the time I had collected about 6 L of product the hydrometer said 5% but my still thermometer never went above 90C.

...this is really very strange. A wash turned to vinegar should reach very fast very high temps like 100°C. How does the distillate taste? Does the 5% taste like 5%?

der wo wrote:Yes. Perhaps a vinegar infection.
But...

Alchemist wrote:My product started coming off fine at about 80 C, I pulled my foreshots, and continued on. The first oddity is that the % coming off per my Tralle Hydrometer said 25% and proceeded to go down from there. By the time I had collected about 6 L of product the hydrometer said 5% but my still thermometer never went above 90C.

...this is really very strange. A wash turned to vinegar should reach very fast very high temps like 100°C. How does the distillate taste? Does the 5% taste like 5%?

It tastes sharp. Acidic sharp. And pH 3.2. A pear stripping run I just tested is 5 or so.

I guess I have vinegar. I'll make a spirit run, and age it on oak. Time to get my titration kit out to get it to 5% after. Bet my still is going to be all shiny

The low pH, the sharp taste. Yes, you have vinegar.
But I don't understand the thermometer reading. Acetic acid boils at slightly higher temp than water.

So, thinking ahead to batch two, if I boil the trub to kill any acetobacteria would I be safe using it for nutrients? And what about the dunder from the still? Safe to continue it's use?

I wouldn't. The acetic acid and the new alcohol will form the ester ethyl acetate probably. It is a maior part of the foreshots.

But on the other hand, rum producers sometimes add cane vinegar purposely to get more esters.

So perhaps it depends on aging, if the rum will benefit from the vinegar or not.