Where does banana flavor in Rum come from?

[der wo]

I recently got a bottle of Forsyths White Rum (Worthy Park distillery) with a very high ester count. It differs from the other two high ester Rums (from Hampden distillery) I own, because of its incredible strong banana flavor. It's cleaner than Hampden, has less pineapple, but it has this strong obvious banana in the front of the flavor.

The perhaps most important difference in the production of those Rums is, that Hampden gets its esters by using infected dunder, but Worthy park doesn't use dunder at all, but let the ferment open for three months at tropical temps. I don't have a picture from their long ferments, but here is one of the Clarendon distillery fermenting open for one month for their Monkymusk Rum:
https://i0.wp.com/cocktailwonk.com/wp-c ... f-1156.jpg" onclick="window.open(this.href);return false;" rel="nofollow
Looks similar like heavily infected dunder.

The most obvious difference between an infected wash and an infected dunder is the ethanol concentration. Dunder has 0% and wash has 6-10%. The result is, that in opposite to the dunder the fermented wash feeds vinegar bacterias (they process ethanol to vinegar). A three months old open ferment will have a very high vinegar concentration, an old dunder almost zero. And when vinegar forms the ester with ethanol (ethylacetate), the distillate will have a glue smell.

Yes, the Forsyths has glue smell too, but the banana flavor is stronger.

Which chemical compounds are responsible for the banana? According different sources banana-esters are mostly from vinegar and higher alcohols (several amyl alcohols). They have lower odor thresholds than the glue-ester, so it needs only small amounts to notice them. But of course the more banana-esters the more banana flavor.
So what a banana smelling Rum needs is a vinegar infection (or added vinegar, many Rum producers simply add cane vinegar somewhere in the process) and much of those higher alcohols. For the added vinegar here a "proof picture" of the "acid tank" of Long Pond distillery: https://i2.wp.com/cocktailwonk.com/wp-c ... f-1156.jpg" onclick="window.open(this.href);return false;" rel="nofollow And you can read in the Arroyo papers something about.
There are a few circumstances, which promote the development of higher alcohols:
- hot fermentation
- high OG
An all molasses ferment in the tropics offers both. BTW, Worthy Park controls the fermentation temp to 30°C.
There are other circumstances, which also perhaps promote higher alcohols. But the sources are contradicting. For example adding yeast nutrients.

And then? In case the low odor threshold of the banana-esters is not enough competing against the glue smell? How get rid of too much of the glue smell but keep the banana flavor? Probably simply with the heads cut. The glue-ester has a much lower boiling point than the banana-esters. Worthy Park cuts 1-2% of the wash volume as fores/heads (200-400l fores/heads, 18000l wash). They have two thumpers filled with high abv feints and it looks like two plates over the second thumper. So it's a relative high distillation, what also means, that the glue smell is well concentrated, and then cutting 1-2% perhaps is enough to get a stronger banana than glue odor. Why not cutting more? I don't know. Speaking for my Forsyths bottle, I think it's good like it is. Generally I think: no glue smell -> no banana flavor.

Here the source of many of the numbers: http://cocktailwonk.com/2016/04/worthy- ... ntury.html" onclick="window.open(this.href);return false;" rel="nofollow

Here...
viewtopic.php?f=39&t=69155
...I wrote "the highest chance to get fusel-esters in a dominating amount is in the dunder pit. Because only here it's possible to have more fusel alcohols than ethanol (because fresh dunder contains almost zero ethanol, but probably many fusel alcohols). But the (fusel-) alcohol strength in dunder is very low for a good esterification rate. So when we use the dunder, it will contain much more acids than esters. And the acids will come in contact to the massive amount of ethanol sooner or later and will build ethanol-esters. Or how much could sulphuric acid help here? Perhaps adding sulphuric acid to dunder before adding the dunder to the low wines or wash gives the fusel-alcohols a head start? I don't know how effective the catalyst works under such bad circumstances (low (fusel-) alcohol strength)."
But looking at my bottle Fosyths, it seems to be very possible without dunder. But dunder still looks more promising for me (perhaps with added cane vinegar?). Unfortunately I cannot judge, how many esters from higher alcohols in my infected dunder esterified Hampden Rums are. I am only able to do this with the Forsyths Rum, because the vinegar-ethanol-ester (glue) smells much different from the vinegar-higher alcohol-esters (banana). The Hampden is more in direction butyric acid esters. And the different butyric esters all smell some kind of fruity. Between for example peach and pineapple (butyric esters) is less difference than between glue and banana.

And I wrote "But are the fusel-esters really needed? How many of you have ever tasted a high ester rum? This stuff is expensive. I only one (but often, I have a whole bottle, Habitation Verlier Hampden LROK). For me it smells possible, that almost only ethanol-esters come from the wash and the dunder, mainly ethyl acetate and ethyl butyrate."
Here my opinion has changed with the Forsyths Rum.

The goal of this post is to inspire the members, who run or plan an infection currently, to think a bit more about vinegar than butyric or lactic infections.

I am currently planing an all molly Rum, hot and long fermentation, playing with cane vinegar, dunder pits, triple Potstill distilled.

I don't know, which cane vinegar the Rum producers use. Probably the cheapest one. But is the cheapest one something industrial large batch tasteless distilled or something raw unfiltered? I have buyed a bottle of cane vinegar in an Asia shop. Tastes not very interesting. All cane vinegar I can get here is distilled. If it has a color, it's E150c. Pretty tasteless, wouldn't buy it again, no advantage over any other vinegar. Perhaps I will make molasses vinegar by myself.