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This ferment represents a departure from the high pH Arroyo style ferments we’ve been exploring. This is our first ferment to go in the opposite direction with high acid, a fission yeast, and a mixed bacteria culture. The ferment went in smelling like cheetos and came out smelling like pineapple! Hopefully this wasn’t a fluke because the results were quite extraordinary.
The yeast in question is a century old fission yeast collected in Jamaica, likely by S.F. Ashby or H.H. Cousins. The mixed bacteria culture was capable of both rum oil production and chain elongation. Completion of a fermentation under these unique conditions may imply symbiosis, but it is hard to pin down the relationship exactly. A budding yeast could not become dominant in this ferment.
Titrateable acidity was roughly 10 g/L with 1/3 being volatile and fermentation duration was over two weeks in a closed fermenter. pH was 4.2 and the F# was in the 300’s. Starting gravity was 1.090. Even though the product is heavy, this is definitely not classical grand arôme territory as defined by Kervegant, which is believed to start at 15 g/L. There is remarkable elegance. This meets Arroyo’s claims that rum is unique relative to whiskies because its new make is so much more palatable.
The old grand arôme rums, of which a few are still made, were essentially concentrates that must be stretched to be enjoyable while I have proposed a new definition where the term could be applied to fission yeast rums that featured a distinct fermentation complication such as a specific bacterial co-ferment. Arroyo often used the term suavity to refer to an ideal where a “heavy” spirit could stand alone with out blending almost like the pure single idea some producers are using.
The suave style grand arôme rums of Arroyo also integrated unique concepts that are currently dormant such as the idea of aging to completion. Under this framework, a rum would be barreled at distillation proof and stored under conditions (tropical being most ideal) where the angel’s share would reduce the spirit to drinking strength with perfect maturity. If you want a spirit to age longer for whatever reason, it may require a higher distillation proof, but increasing the ABV eventually works against quality. A lot could be said here, but what this means is that both quality and marketing emphasis shift back to the fermentation. Once the spirit hits the barrel, the countdown begins and everything must be in place for a perfect conclusion. It is the ultimate garbage-in / garbage-out. I do believe this high acid fermentation could produce a product worthy of aging to completion.
I actually made an error with the birectifier, but that does not void all the results. What happened was that I must have loaded less than 100 ml of absolute alcohol. The first three fractions align correctly but then at the forth alcohol drops off too quickly skewing the alignment. What I did was simply change to the fifth fraction early based on temperature which realigns the fractions. The only fraction that become void is the forth because it is not a full 25 ml. I think I only collected 15. This error was easy to notice because I was working at the other side of the room and my attention was caught by an incredible aroma. When I investigated and saw the volume collected relative the temperature it was clear what happened and easy to correct course. This does mean that every other fraction would also be 5-10% less concentrated than they should be, but that is fine for evaluating this ferment. However, I believe this fusel oil content to be well below that of a budding yeast and would love to evaluate that accurately.
Hopefully this will be one of many successful high acid ferments and I can push the boundaries all the way into grand arôme territory. What I’m experiencing here is what I believe everyone developing new rums is looking for. This is a Jamaica style ferment brought to life outside of Jamaica (with extra details learned from Arroyo). We’re starting to frame in the numbers with simple analysis procedures and feel this style can be taught if producers can handle growing their own yeast.
This ferment did begin with a starter and we’ve learned an extraordinary amount in that regard. Fission yeasts are considered slow growers under typical conditions. We’ve overcome this with a lot of research and experimentation and found they can be grown as efficiently as a budding yeast. Fission yeast starters may help control risk and reduce variability in these chaotic processes.
There is a lot more I could say, but I probably shouldn’t until I can duplicate more of the work.
Fraction 1: Significant ethyl acetate, but also a fruitiness. Not quite concentrated to the point of being non-culinary. This is probably a really good level for a new make. This no doubt may give the spirit a great head start on maturation.
Fraction 2: More neutral than I’d imagined given the first fraction.
Fraction 3: Very neutral.
Fraction 4: Definite light amount of fusel oil, but hard to evaluate due to how the charge was improperly scaled.
Fraction 5: Visible louche and appreciable droplets on the surface. Glorious beautiful ester aroma. Definite rum oil aroma. Remarkable persistence. This fraction doesn’t have power so much as elegance. Put this in a barrel! The aroma is remarkable, but unlike other concentrated fraction 5’s, this isn’t so acrid on the palate.
Fraction 6: Slight rum oil aroma. Definite gustatory acidity.
Fraction 7: No off aromas, subtle gustatory acidity.
Fraction 8: No off aromas, subtle gustatory acidity. No distinct acetic acid.