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Ester formation in the column still

edited February 2020 in Recipes

I understand that running your column still with the deflegmator cranked all the way up for an hour or so will increase the ester formation within the column and then you can dial down the deflegmator and start drawing down spirits.

The other essential component to ester formation in the column is pH.

Does it matter what acid is used to lower the wash pH?

The wash pH is normally around 5.2 but I was looking to lower it down to 4.0 to enhance ester production in the column.

Has anyone experimented with different pH reducers? H2SO4? HCL? Citric acid? Malic acid?


  • What would be the reason to enhance ester production during the distillation process?

  • I HIGHLY suggest reading

    The Big Rum Thread


    The Big Dunder Pit Thread

    Seriously, spend days reading those... worth every second of your time.

  • Will do...thanks.

  • edited February 2020

    Driving Fischer esterification in the still via extended duration refluxing is going to see better performance if you use a mineral acid catalyst. Typically, Sulfuric Acid is used in the lab, and if you read the old rum literature, you'll see it commonly referenced in high ester and heavy rum production. While other acids (citric, malic, etc), will not have the same impact as sulfuric, there is a lesser impact of increasing acidity generating/preserving more esters.

    Keep in mind that there is a little bit of a balance here. While extended duration refluxing will create more esters, more plates will concentrate those esters more tightly than fewer plates will (smear). Extended refluxing, combined with a big heads cut - is somewhat counterproductive.

    If you are stripping first, extended refluxing may also be counterproductive, depending on how deep your strip has gone. If you don't have the heavy alcohols, and carboxylic acids - you are only going to create lots ethyl acetate - which isn't a positive. (This is because you'll likely have lots of acetic acid and ethanol in a "tight" strip).

  • If you want esters a column isn't the place to do it. Like Grim said there's several issues why you should look other places. Fermentation is the best place creating the most complex esters and precursors. Longer ferments will give you more of the higher alcohols/fatty acids. You want that chemical diversity to create better esters. Yeast will use those to enzymatically create longer chain esters.

    If you want to create lots of esters during distilling yes lowering pH will help. But the still you use matters more - a pot still with a tall column (not plated/packed) run slow will create esters. Better is a thumper/retort(s) via the Cousins Process. But you probably don't have much choice as you already have a still. For a column run it fast and dirty to get as much smearing as possible. That's what will make the most esters post fermentation. Esters are a dirty business. You need to get them or their precursors in before you start aging.

  • edited February 2020

    @SingleMaltYinzer said: Esters are a dirty business.

    Need to put that on a tee shirt...

    StillDragon North America - Your StillDragon® Distributor for North America

  • I think I want one of those tee shirts.

    Zymurgy Bob, a simple potstiller

    my book, Making Fine Spirits

  • edited February 2020

    You can not compare the the Jamaican double retort method with column or even pot distillation. No comparison exists, it lives in it's own universe of a very specialized form of reactive distillation.

    By charging the thumpers with early tails, and late tails, you creating a situation where you are exposing two components that do not normally co-exist at the same point in the run. The thumper charges have a wide range of heavier alcohols and acids, that would normally be distilled at different points in time during the the process, and you are making them meet and react with the vapor components from the main pot. The other factor is that the late tails are in the last thumper, meaning significantly more of the acids will carry through to the distillate than would in a typical batch run.

    This phenomenon will never exist in a typical batch still, pot or column.

    Even if we're talking about a traditional pot still and thumper, where the thumper is charged with higher proof hearts - or even strip - you still aren't creating the same kind of situation as charging with only the early and late tails components.

    The Cousins process makes this phenomenon even more complicated by playing with pH to create a very high ester situation. These reactions would simply never exist in normal fermentation and distillation - better living through chemistry.

  • edited February 2020

    Here is a great new paper on extended fermentation and distillation styles (pot/column) for rum.

    Effect of ageing on lees and distillation process on fermented sugarcanemolasses for the production of rum @

  • Thanks for the input everyone.

    I made a rum a year or so ago from a single back-set from a previous fermentation and nothing form a dunder pit. I used a chardonnay wine yeast and the chardonnay notes really came through with the traditional rum notes. It was very pleasant to the nose but did not meet the taste standard I was shooting for. Looking back I believe I combined too many heads and tails with the hearts... I got too greedy. I really need to stay disciplined and just select the heart of hearts.

    My next rum experiment I plan to use panela only. Start my dunder pit from the first run and use the back-set though five generations. I'm going to use a four plate column with procaps using direct steam. The plan is to clarify each fermentation as much as possible before it's distilled and only use the distillate above 84% (+/-1%). I just seem to enjoy the lightest of light rums with banana, flowery least that's what I'm shooting for.

  • You may find rum lacking in the rumness if you use only mid hearts.

    Not as eloquent or technical as the other guys, but late heads at least are needed imo.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • @grim said: Here is a great new paper on extended fermentation and distillation styles (pot/column) for rum.

    Effect of ageing on lees and distillation process on fermented sugarcanemolasses for the production of rum @

    Thanks - that's a good one. Looks like the Coffey column still really removes acids (Page 4, figure 2A) . Not sure what Page 5 figure 3A means. I'm assuming it means there just more "stuff".

  • I've got to plead ignorance. Aside from the "sharing" URL, which seemed to be more of the same, the only link I could fins was the "save", and I have no idea where it saves to. I'd really like to see this. The whole series, really.

    Zymurgy Bob, a simple potstiller

    my book, Making Fine Spirits

  • Ok, it just prefers Edge to Firefox.

    Zymurgy Bob, a simple potstiller

    my book, Making Fine Spirits

  • I think it confirms a lot of what we’ve talked about here around dark rum fermentation, longer is better.

    Sometimes those forgotten batches are pretty special.

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