"Pure" Esters Rum, Input Requested

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skrum
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"Pure" Esters Rum, Input Requested

Post by skrum »

I've been making an acceptable rum for a while, but would like to be more educated so I can steer the process in directions I'd like. So I'd like to make some "doctored" spirits to highlight the esters produced by certain acids.

My intended process is
1) Start with about 0.5-1 L of 40% neutral alcohol in my 4L mini still boiler.
2) Add a single carboxylic acid
3) Adjust down pH to 3.4-3.7 using sulfuric acid (carefully, using PPE)
4) Heat the boiler to 60 C and allow reactions for around 12 hr
5) Slowly distill the results, separating cuts regularly
6) Evaluate the results by smell and taste in an attempt to identify desirable and undesirable esters
7) Repeat for a variety of acids

Acids and Sources:
Acetic Acid: Vinegar
Propionic acid: *
Butyric acid: sodium butyrate food supplement
Valeric acid: *
Caproic acid: *
Enanthic acid: *
Caprylic acid: food supplement
Benzoic acid: sodium benzoate food preservative
Malic acid: wine additive
Lactic acid: pH control in beer and sour flavouring
*=I haven't yet found a good source

Not so pure:
Formic acid: raspberries
Laurel, caprylic and capric acid: coconut oil
Various: my dunder pit

I'd like everyone's general comments, but I think my specific questions are:
a) what quantities of carboxylic acids to add? The Lime Salts thread talks about 2 g per 5.5 gallon ferment, but that's in fermentation rather than low wines.

b) is step 3 correct? Should I be adding the sulfuric acid by pH or by some other method (titrating with something?), and if by pH, what pH? The numbers above come from this thread but I'm not certain of whether the pH has to actually be lowered, or if there just needs to be a small amount of excess to act as a catalyst. I've seen acid volumes range from 1 mL in 2000 L to 0.5 mL in 100 mL, so I'm not sure what a normal amount would be.

c) I'm proposing using neutral alcohol as the base, but would it be better to use a light rum? Are the complimentary flavours required?

edit: somehow I forgot about the "Pure Acids and Esters" post, and der wo's brave smell and taste tests , which are similar, but not distilled. Have added lactic acid to the list.
Last edited by skrum on Mon Jan 31, 2022 9:23 pm, edited 1 time in total.
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Re: "Pure" Esters Rum, Input Requested

Post by still_stirrin »

Waaay above my “payscale”.

I make rum with fancy or feedstock molly. I don’t dunder, or wonder. But there are other rummys here who know a lot more about rum than I do. But it seems like all the “lab work” with acids and bases is too OCD for me. I think time (maturity) is a key feature to a good rum. The exotics are demographically driven by the environment and available fermentable sources (what you got, so use it). Wild flora may also have some influence on the product too, as that can affect the aromatic and flavor congeners.

Good luck, but be safe with your “chemistry”.
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Re: "Pure" Esters Rum, Input Requested

Post by Single Malt Yinzer »

You're treading were few have gone before. I don't believe that you're going to find too many direct answers. Your experiments will lead you to those answers.

* Based on your post you're going to be using Fischer Spier esterification (aka reduction). You seem to be setup really well for that.
* If you're exploring what esters/aromas/flavors you get then use a neutral spirit so the end result isn't tainted by the source material.
* The best way to do it is to make sure you record all of the data in detail. Start with small amounts and then increase them. For each experiment change -ONE- factor. This will give you the cleanest and most usable results. Again,it looks like you have this covered.
* Once complete take tasting notes and try it every week for a month or so. Flavors can change over time. You want to see what stays and what goes away with time. You're creating a highly reactive state with your experiment. Once the spirit cools down and achieves stasis the chemical composition may have changed.
* Transesterification can take place as the spirit is rested. This is when a higher polarity molecule replaces a lower polarity molecule in an ester. This is partially what happens when the flavor changes when spirit is resting.
* Once you figure out what you like then try it in a spirit with flavor. The spirit with more flavor will have a more diverse chemical composition. This will effect your experiment & flavor. Luckily it's usually for the better.
* Esterification is effected by ABV. The higher the ABV the more esters can be made. The lower the ABV some and esters will be destroyed and the esterification reaction will be harder to make happen.
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

Good point on the neutral vs rum issue. I can always add the rum flavors later, but can't remove them.

Is there a limit to how high the ABV can be before causing issues? I can start with near-azeotrope neutral and then dilute just before distilling. I'd imagine that acid-base chemistry is pretty different in a a high ABV solution. Would a pH meter or test strips even work? This may a moot point since a lot of the literature I've read on Fischer Speier esterification involve using very small amounts of sulfuric acid.

edit: upon further reading, it looks like the standard laboratory Fischer Speier esterification is done with pure alcohol, so my near-azeotrope should be appropriate.
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Re: "Pure" Esters Rum, Input Requested

Post by Single Malt Yinzer »

Yes, if your aim is esters as close to azeotrope as possible.
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

After a long break, I finally got back to this project and have the first results to report, which I classify as a success!

My first target is benzoic acid, an aromatic carboxylic acid with formula C6H5CO2H. I got it in the form of sodium benzoate which is commonly available as a food preservative.

I mixed in my boiler:
  • 500 mL of relatively neutral 96% Birdwatcher's neutral spirit
  • 50.2 g sodium benzoate granules
  • 5 mL acid catalyst (edit: removed name of dangerous acid, if you know enough to do this safely, you should know what acid to use)



I heated this to 60 C for about 6 hours, occasionally swirling to mix.

I measured the pH at 5 (using test strips) at the start of the 6 hours.

I noticed that the granules didn't noticeably dissolve in the high strength ethanol. When I added the acid catalyst, the granules immediately starting dissolving in that area. Not sure if this was due to the acid or to the water contained in it. After 6 hours the solution was milky but there was a considerable amount of undissolved material on the bottom.

I then added 700 mL of RO water to bring the ABV down around 40%. Most, but not all, of the granules then immediately dissolved.

I assembled the worm condenser and heated to boiling (I overshot a bit and got a stream of product before I could dial down the power to a drip). Then ran the rest of the run at 30% power (285 W) until I had collected a total of 459 g of product, divided into ten 10 minute cuts. The distillate was crystal clear throughout with no cloudiness. The stillage left in the boiler at the end was also clear with no remaining solids. Edit: after cooling, the stillage formed a number of clusters of very fine needle-shaped crystals.

My initial perceptions (immediately off the still) are:
First cuts (first 150 g): odorless when undiluted. Mixing 50:50 with water produces a mild, fruity aroma. Mild, pleasant, fruity, taste when diluted
Middle cuts (next 150 g): aroma mild when undiluted, strong when diluted 50:50. Diluted, taste is quite strong but palatable. Odor and taste same as first cuts but stronger.
Last cuts (next 150 g): Similar to middle cuts but stronger. Diluted, taste is very strong, leaves an aftertaste, more medicinal.

The taste and aroma seem to be consistent throughout, only varying in strength. It is very specific and memorable (at this concentration). I immediately went back into my closet and found a chokecherry brandy that I recalled the taste from and *bam*, exactly the same. (My research shows that benzoic acid is present in chokecherries but I can't find any information on concentration or the presence of its esters.) I can't recall experiencing it in any other situation, though. Never in detectable levels in rum, but the perception might be different at lower concentrations (will try this later).

So I've produced *something* with a strong, specific, identifiable taste and related aroma. I guess it's probably ethyl benzoate. Wikipedia says "As with many volatile esters, ethyl benzoate has a pleasant odor described as sweet, wintergreen, fruity, medicinal, cherry, pish and grape." My perception would agree strongly with sweet, fruity, and medicinal; agree weakly with cherry and grape (maybe red grape skins); I detected no wintergreen and don't know what pish is.

I took considerable notes in a notebook, so I certify this as "science".
Last edited by skrum on Thu Aug 11, 2022 7:05 pm, edited 3 times in total.
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Re: "Pure" Esters Rum, Input Requested

Post by Demy »

And I was convinced that rum was made from molasses .... :ebiggrin: :ebiggrin: :ebiggrin: :ebiggrin:
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

Results #2: Ethyl Propionate

I repeated the above, but used 50 g of sodium propionate (a fine white powder used as a preservative for baked goods)

During the heated hold in 96% ethanol, most but not all of the powder dissolved. I measured pH 7 (maybe should have added more acid but wanted to maintain consistency)

Once diluted with water just prior to distillation, the last of the powder quickly dissolved.

I took 10 cuts over 140 minutes, totalling 498 g of product. There was nothing detectable beyond what one would expect from the neutral spirits in the first 300 g. The next 150 g resulted in a mild flavor and aroma, increasing in potency in later cuts. It was sharp and chemical, not nice, not familiar. In the last 50 g, the ABV dropped, leaving a watery product, with the chemical taste becoming overpowering and unpalatable.

Ethyl propionate is described as having a pineapple-like odor, but I didn't experience this at these concentrations. Like the benzoate, I may need to taste it diluted with neutral to near the taste threshold.
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Re: "Pure" Esters Rum, Input Requested

Post by Yummyrum »

skrum , I applaud your efforts , but I get an uneasy feeling hearing that you are using 95% abv in a boiler for your experiments . It’s not a procedure that this board approves of .

I would strongly suggest you use a Laboratory electronic Heating Mantle if you wish to do further playing . Please be safe .
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Re: "Pure" Esters Rum, Input Requested

Post by acfixer69 »

Not only concerned with the high ABV but the chemical recipe is way over the top for the average home distiller.
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

> I get an uneasy feeling hearing that you are using 95% abv in a boiler for your experiments .

I'm not distilling at 96%, I dilute to 40% before running it.
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Re: "Pure" Esters Rum, Input Requested

Post by StillerBoy »

acfixer69 wrote: Thu Aug 11, 2022 4:32 pm but the chemical recipe is way over the top for the average home distiller.
acfixer.. It would be appreciate if you would define what you meant and intented by the about statement on the "chemical recipe is way over the top" and "the average home distiller"..

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Re: "Pure" Esters Rum, Input Requested

Post by Saltbush Bill »

Its really very simple to understand Stillboy .....he means that sooner or later someone is going to get hurt stuffing around with all of these acids and chemicals.
FWIW I agree 100% with him......its an accident waiting to happen and not something I think should be encouraged.
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

OK, I've removed mention of the dangerous acid. It appears that I can't edit the original post, can a mod redact it there too?
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Re: "Pure" Esters Rum, Input Requested

Post by Yummyrum »

skrum wrote: Thu Aug 11, 2022 5:35 pm > I get an uneasy feeling hearing that you are using 95% abv in a boiler for your experiments .

I'm not distilling at 96%, I dilute to 40% before running it.
Oh sorry , yes I see where you mentioned that .

Personally I see no need to edit out what acid you used. It has been mentioned on similar topics here before . I guess I’m used to handling it at work so I feel more comfortable than others about it .

None the less , it should only be used by those that fully understand the dangers and know correct handling procedures.

I think this estification stuff is certainly not fir the majority of home distillers . There are a small minority that are interested . So long as it’s done thoughtfully and safely, I see no problem……. But thats just me .
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Re: "Pure" Esters Rum, Input Requested

Post by NZChris »

I've been using the 'deleted' acid when making rum for over thirty years. It's not an uncommon part of the process in the industry and most rum research documents refer to it's use.

What I don't do, is buy the precursors and pretend to make rum with them. I extract my own rum essences from rum ferments and distillations using methods already discussed on the forum and use them to bolster the flavors in the rums they were extracted from when I do the final blending.

I have no idea why a home distiller would want to cobble together an artificial rum without using cane juice or it's derivatives. You are welcome to explain it. If it's a good reason, you might get better help.
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

>I have no idea why a home distiller would want to cobble together an artificial rum without using cane juice or it's derivatives. You are welcome to explain it.

My goal here is more for my own sensory education than to doctor up a rum for production. For example, previously I had no idea what the dominant flavour in my chokecherry brandy was. Now I have some evidence it's a benzoic ester.
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Re: "Pure" Esters Rum, Input Requested

Post by Ben »

From a sensory training standpoint it makes a lot of sense. You can intentionally produce some of these things in ferments, butyric, lactic, acetic are low hanging fruit... Ingredients like molasses or gypsum can get you the sulfuric but it's hard to pick out what is doing what with everything else that happens in a ferment. Cool experiment, I look forward to seeing more of your results as you work through this.

There may be a missing link in the esterification process which is esterification in the fermenter/dunder pit after the yeast have had their way. When people talk about dunder pits and dirty rum ferments my mind immediately goes to Brettanomyces, Lacto, and Pediococcus. They all three produce esters, and may be producing something different tasting than what you are getting in the boiler from the heat esterification cycle. This would be a little more difficult to isolate, but you could set up a protocol to make it happen.
Ester-Table-1.jpg
:)
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Re: "Pure" Esters Rum, Input Requested

Post by bluc »

Great chart. At one time or another i have had all those flavours in rum. :thumbup:
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Re: "Pure" Esters Rum, Input Requested

Post by bluc »

Ethyl isovelerate. "Fruity" are we talking tropical or dark dried fruit.
I get dark dried fried like rum raisen ice cream rum from severely underpitching bakers yeast..
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Re: "Pure" Esters Rum, Input Requested

Post by Saltbush Bill »

bluc wrote: Mon Aug 15, 2022 10:56 pm rum raisen ice cream rum from severely underpitching bakers yeast..
You've just made my mind up for me Bluc.......been going to play around with under pitching for quite some time.....never did yet though.
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Post by Ben »

bluc wrote: Mon Aug 15, 2022 10:56 pm Ethyl isovelerate. "Fruity" are we talking tropical or dark dried fruit.
I get dark dried fried like rum raisen ice cream rum from severely underpitching bakers yeast..
Think green apples. You will find it pretty commonly in Irish whiskey and ales. A ferment with US04 or whatever irish ale strain can provide it.

If you are looking for more of the tropical fruits you could try intentionally introducing butyric into your ferment, counter it with baking soda in the low wines which tends to leave pineapple. wyeast 1056 or us05 will throw citrus or peach when fermented at low 60's. A20 yeast is nicknamed citrus, it might get you there. Overall pH will also effect your perception, if you are acidic its going to have more of the citrus twinge.

You might play with Brettanomyces in small batch ferments (like 1l). See if you like what it does, you can buy brett commercially, pull a liter of your wash before distilling and add the brett, it converts alcohol and will take time but you can see if you like what its producing.
:)
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Re: "Pure" Esters Rum, Input Requested

Post by bluc »

Saltbush Bill wrote: Mon Aug 15, 2022 11:28 pm
bluc wrote: Mon Aug 15, 2022 10:56 pm rum raisen ice cream rum from severely underpitching bakers yeast..
You've just made my mind up for me Bluc.......been going to play around with under pitching for quite some time.....never did yet though.
I have gone as low as 1tblespoon bakers in 200l ferment. And ferment hot.
Normally doesnt kick off properly for 48-76hrs.
I do 50/50 rum but cant see why wouldnt work for your 100% mol mix.
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

Results #3: Caprylic (A.K.A. Octanoic) acid

I acquired this acid in the form of gel caps for nutritional supplement use. Again, I added 50 g (as per the per capsule active ingredient labelling) to 500 mL of 96% ethanol with 5 mL of acid catalyst. This time the pH was around 3 (not surprising that it's lower this time since I'm now working with the carboxylic acid rather than its salt). The acid appears as a clear liquid that mixes easily with the alcohol. Unfortunately, I had forgotten that the gelatin of the caps is not soluble in ethanol so the gel caps softened but didn't release their contents. I had to cut 83 squishy caps with scissors. The solution was clear and had no noticeable aroma.

I held this at 60 C for 10 hours, with no change in appearance (clear) or aroma (little). When I added 700 mL water to bring it down to 40% ABV, the liquid immediately turned milky and oily droplets floated on the surface. A very strong aroma emanated. I haven't spent much time with goats but people associate caprylic acid with goats and I'd believe it. It's musky and rancid.

I started distilling the liquid and right from the first drops, it was very heavy in aroma and taste. Similar to the musky aroma that was produced prior to distilling, but concentrated. Concentrated to the point where one drop on the tongue is unpleasant and leaves an aftertaste for minutes. Similar aroma. I did test a few drops in about 30 mL of water and there was still a strong flavour with some hints of pineapple (one of the tastes from the literature). I think I did recognize this from rums. Like the previous esters, I will taste the diluted product more systematically later.

It's too strong to really taste properly, but I feel like it got less overpowering as the run progressed so this is something you might find near the heads of a rum. Other than the concentration, I don't think the aroma changed much over the course of the run, so it's probably mostly a single chemical.

Again, I think I've produced a single identifiable chemical and it's probably ethyl caprylate (a.k.a. ethyl octanoate), so I'm calling this a success.
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Post by Yummyrum »

Keep’m coming .

I like that you are sourcing readily available chemicals .
Curious as to how you decide how much acid to add ?
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

Yummyrum wrote: Tue Aug 16, 2022 11:00 pm Keep’m coming .

I like that you are sourcing readily available chemicals .
Curious as to how you decide how much acid to add ?
I had replied earlier, but apparently it got eaten in the phpBB Upgrade of 2022. In any case, the answer is: it's pretty arbitrary. If you add too much you lose some efficiency due to unreacted acid at the end and if you add too little you get less product. I tried to guess an amount that would entirely dissolve or mix with the alcohol, and so far it seems like that happened.
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Re: "Pure" Esters Rum, Input Requested

Post by skrum »

Results #4: Lactic Acid

Some of the previous acids were just guesses, but this is probably an important one. Almost all ferments would include at least trace amounts and it's also an easy acid to promote by allowing lactic acid bacteria to do it's thing. It is also commonly used in beer brewing for mash pH control, so is readily available and trusted.

Same procedure and amounts as before (added 56 g of 88% lactic acid to net 50 g of acid).

The solution was clear with no precipitate at any stage of the process, except for the stillage which was a forest green. Anyone have any idea what this could be?

The first 100 mL of product was contaminated with the previous run's caprylate. I cleaned much more carefully than I usually do, but it still came through clearly. Even some of my glassware was contaminated after washing twice. At these levels, it's still barny but more fruity.

The following 200 mL was relatively clean tasting and smelling with a slight earthy taste. Maybe a change in texture but I find it hard to recall this from one drink to another.

The last 100 mL had a strong but not overpowering taste that I'd relate to roasted or smoked meats, with a hint of pineapple. This would definitely be in place for a whiskey and probably a rum. It would probably come over near the tails (this is also what I've seen in some papers on congeners like this one).

The literature talks about "creamy" and "buttery" for ethyl lactate but I didn't get that at this concentration. I did get the described "pineapple".

I have a good taste for the lactic acid (sour like sour candies) and there was no trace of that in the distillate.
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Re: "Pure" Esters Rum, Input Requested

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Ben wrote: Tue Aug 16, 2022 7:08 am
bluc wrote: Mon Aug 15, 2022 10:56 pm Ethyl isovelerate. "Fruity" are we talking tropical or dark dried fruit.
I get dark dried fried like rum raisen ice cream rum from severely underpitching bakers yeast..
Think green apples. You will find it pretty commonly in Irish whiskey and ales. A ferment with US04 or whatever irish ale strain can provide it.

If you are looking for more of the tropical fruits you could try intentionally introducing butyric into your ferment, counter it with baking soda in the low wines which tends to leave pineapple. wyeast 1056 or us05 will throw citrus or peach when fermented at low 60's. A20 yeast is nicknamed citrus, it might get you there. Overall pH will also effect your perception, if you are acidic its going to have more of the citrus twinge.

You might play with Brettanomyces in small batch ferments (like 1l). See if you like what it does, you can buy brett commercially, pull a liter of your wash before distilling and add the brett, it converts alcohol and will take time but you can see if you like what its producing.
More a fan of dark fruits on rum. Raisins prune date alongside tabacoo and and leather makes for a great drink. Any ideas how to get the dark fruits Im all ears. Underpitching gets it reliably but
Hearts takes a big hit volume wise. I dont know if Im getting this flavour purely from the yeadt or from local bacteria.

Everyday Session rum generally go for a more bland rum with a small amount of oak influence. Lets the mollasses natural flavour shine enjoy it with coke pr pepsi max....
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Re: "Pure" Esters Rum, Input Requested

Post by Hügelwilli »

skrum wrote: Tue Aug 23, 2022 1:56 pm Results #4: Lactic Acid
Ethyl lactate is not very volatile at high abv. In a spirit run it comes over more in the tails. Perhaps you would have to dilute more before distillation? Or don't rectificate in case you refluxed it?
The reason is because the chemical structure of lactic acid is very different from the most other acids you will try out (formic, acetic, propionic, butyric, valeric for example).
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Re: "Pure" Esters Rum, Input Requested

Post by Ben »

bluc wrote: Wed Aug 24, 2022 1:18 am
Ben wrote: Tue Aug 16, 2022 7:08 am
bluc wrote: Mon Aug 15, 2022 10:56 pm Ethyl isovelerate. "Fruity" are we talking tropical or dark dried fruit.
I get dark dried fried like rum raisen ice cream rum from severely underpitching bakers yeast..
Think green apples. You will find it pretty commonly in Irish whiskey and ales. A ferment with US04 or whatever irish ale strain can provide it.

If you are looking for more of the tropical fruits you could try intentionally introducing butyric into your ferment, counter it with baking soda in the low wines which tends to leave pineapple. wyeast 1056 or us05 will throw citrus or peach when fermented at low 60's. A20 yeast is nicknamed citrus, it might get you there. Overall pH will also effect your perception, if you are acidic its going to have more of the citrus twinge.

You might play with Brettanomyces in small batch ferments (like 1l). See if you like what it does, you can buy brett commercially, pull a liter of your wash before distilling and add the brett, it converts alcohol and will take time but you can see if you like what its producing.
More a fan of dark fruits on rum. Raisins prune date alongside tabacoo and and leather makes for a great drink. Any ideas how to get the dark fruits Im all ears. Underpitching gets it reliably but
Hearts takes a big hit volume wise. I dont know if Im getting this flavour purely from the yeadt or from local bacteria.

Everyday Session rum generally go for a more bland rum with a small amount of oak influence. Lets the mollasses natural flavour shine enjoy it with coke pr pepsi max....
WLP099 and push your starting gravity up some, say 1.080-1.100, ensure your nutrient regimen is good, ferment mid-high 60s, you can let temp raise up after 3 days. I would split and recycle the yeast for many generations. You could also try turning some of your sugars to Belgian dark candy, invert and cook it to a dark level, add water directly to get a syrup (clean up can suck if you let it set up hard).
:)
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