Birectifier Analysis of an Extreme Duration Rested Ferment

An extreme duration rested ferment under very high acid conditions sounds like a sexy idea, but there wasn’t too much magic going on. This ferment, however, teaches a lot of lessons. This came to be because my basement flooded and the clean up was arduous among an already jam packed schedule. This ferment actually sat around for many months. It did finish at an ABV of about 7% which is a great success in the realm of high acid, high VA ferments.

One theory that this case study adds weight to refuting is that staling, or sitting around, under high acid conditions may be important to the formation of rum oil. This rum was estery, but had no obvious rum oil, and basically no radiance.

Staling was one of our original lines of inquiry for figuring out what exactly makes Jamaica rum so special, but it may be something we can cross off the list to focus on other more likely targets. Many studies looking at damascenone levels in a broad array of food stuffs described its ability to increase under acidic conditions but that may only be at baseline levels and the amounts found in the finest rums may be well beyond that.

Something else that popped up may have been ethyl formate in the first fraction which I have only learned to detect organoleptically after seeing a unique sample recently.

Butyric acid did reveal itself in this ferment and that may have been the most significant product of the extreme duration. Butyric acid bacteria grows extremely slowly under such acidic conditions, but here it was given plenty of time which would likely never be viable in a real world scenario.

It was very surprising that the ABV was so good despite the high acid conditions and very high level of volatile acidity.

Something else this case study emphasizes is the importance of the radiance concept. This was certainly an estery rum, but it felt hollow. It is missing whatever magic valorizes esters. My theory is that bland lactic acid bacteria has dominated the ferment and it has lost all wild character capable of producing rum oil under acidic conditions. Fission yeasts can produce rum oil themselves at high pH while very unique lactic acid bacteria is the likely culprit under acidic conditions.


Fraction 1: Concentrated just to the point of non-culinary aromas. Likely the most ethyl acetate I’ve produced in a new make. Possible ethyl formate character very light but similar to what was the in recent butyric bacteria ferment from Cory.

Fraction 2: Diminutive version of fraction 1.

Fraction 3: Fairly neutral as expected.

Fraction 4: Definite presence of fusel oil plus an estery fraction 5 quality. Light fusel oil inline with a fission yeast.

Fraction 5: Visually cloudy. Very estery but no rum oil quality. No radiance. Detectable gustatory acidity.

Fraction 6: Slightly less gustatory acidity but very much like fraction 7.

Fraction 7: Fairly identical to fraction 8.

Fraction 8: Detectable butyric acid on the nose, but nothing too obvious. Significant gustatory acidity.

Stillage: Significant acidity and copper salts.

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