Holding kettle temperature to affect distillate flavour

Distillation methods and improvements.

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Birrofilo
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Holding kettle temperature to affect distillate flavour

Post by Birrofilo » Wed Apr 22, 2020 10:16 am

I was reading a thread, recently closed, where I found these interesting quotes by user @cayars.

"Certain flavors such as "butter" can be brought out by controlling boiler temp for a specific duration followed by ramping up temps. Certain flavors can be altered by holding the boiler contents at specific temp ranges."

"What I was talking about is bringing out flavors by holding at certain temperatures like 135 F for X period then continuing to boiling point. Some flavors can be brought out by going to 145 F for X period, then drop back to 110ish F for Y period followed by going back to boiling. Different temps holds during the warm up can affect flavors especially at the correct pH.

This is an area of the hobby/profession that hasn't gotten much coverage around here possibly because people lack the ability to control this consistently. I think I've only seen one thread (Butter Rum) that touches on this to some degree but was done a bit differently. using an extended or overnight rest (not needed)."

That thread died of a dogmatic dispute on the meaning of temperature, heat, temperature control etc. and I am not interested into reviving that at all.

I am interested in this concept of influencing the flavour of the final product by executing some "pauses" at certain temperature in the kettle, at some pH, presumably in order to create some chemical reactions/compounds, before actually starting the distillation process (before starting the boiling of the broth). It seems very interesting and yet very new to me, actually it's "unheard of" as far as I am concerned.

I would be grateful, and I think it would be of great service to the community, if cayars or any other user would elaborate on this or would point ot me some source on this subject.

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Re: Holding kettle temperature to affect distillate flavour

Post by GCB3 » Wed Apr 22, 2020 10:42 am

Here is a link to ShineOn’s thread. It may be of some help to you.

viewtopic.php?f=101&t=70778#p7524137

I have not tried this but plan to next time and make some room.

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Re: Holding kettle temperature to affect distillate flavour

Post by Birrofilo » Wed Apr 22, 2020 11:39 am

Thanks GCB3 for your answer.
I read the thread.

As far as butter flavour is concerned, I do suspect the cause is diacetyl, as I never met any aromatic ester which is described as imparting a buttery smell.

Two questions arise:

a) Besides this method explained by ShineOn to increase the buttery flavour, is there some other kettle temperature pause which favours some different kind of flavour/aroma? Could we obtain some phenolic aroma, or some fruit aroma, by favouring esterification with rests at different temperatures?

b) Although I tend to trust the method by ShineOn is working, as this was confirmed by other users, I wonder which is the mechanism. Diacetyl should be produced during fermentation. If you want a broth which is rich in diacetyl, the best is to "stress" the yeast (high density, high temperature, low pitching rate) and especially to cut temperature and bring the beer to the still before the yeast has had the time to "clean up" the diacetyl. Yeast will first consume all sugars it can consume, and then will begin "eating" the diacetyl which it left in the broth during the initial phase of the fermentation. (In beer making, and especially in lager production, a "diacetyl rest" is often performed in order to allow the yeast, after the beer reaches final gravity, to reabsorb the diacetyl which was produced earlier). One can obtain a high level of diacetyl by measuring density every day and when it reaches final gravity "crashing it cold" (or just racking it). FG can be known in advance by making a separate fast fermentation with a small beer sample (put some broth from the already inoculated fermentor into a jar and let it ferment at higher temperature than the bulk: the beer will reach a certain FG and that is the FG that the bulk will also reach, barring infections that is).

Diacetyl is created by the yeast by a chemical reaction, decarboxylation, applied on acetolactate (acetolactic acid), that should be acetolactate decarboxylase (It's Greek to me but until now makes some sense).

It might be that some acetolactate is not "worked" by the yeast, and it arrives in the kettle. In the kettle some chemical reaction should happen, and maybe it is the acetolactate decarboxylase, which creates some diacetyl which was not in the beer.

It would be interesting to know if this reacton works best at 135 °F (57 °C) or if there is maybe a temperature where the tricks works even better (a higher temperature maybe, there is some margin before boiling).

Or it might be that the acetolatic acid, being an acid, reacts with some alcohol in the broth to form an ester which actually smells like butter or butterscotch.

Finally, one might wonder whether adding some lactic acid to the broth might favour the raise of the butter flavour: if it works with acetolactic acid, *maybe* it works with lactic acid as well. That would give full control on the amount of the butter flavour (you want more? You just add some more ml of lactic acid to the broth). Lactic acid is something that many all grain brewers use, it's cheap, it's not dangerous, it probably is already in your cupboard.

I plan to do my first distillation this June (finally! It's two years I am just reading and buying, I think I will deal with sugar washes for all my first year of still practice) but I think, maybe heretically, that a touch of butter would not be bad also in a brandy or in a whisky, not just in a rum.

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Re: Holding kettle temperature to affect distillate flavour

Post by LWTCS » Wed Apr 22, 2020 1:32 pm

Pretty sure there is some additional dialog buried somewhere here that talks about techniques used to enhance Fischer esterfication.
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Re: Holding kettle temperature to affect distillate flavour

Post by NZChris » Wed Apr 22, 2020 1:40 pm

Been doing it for years. Having a large element to get up to distilling temperature quickly, shortens the time available for esterification while the alcohol level is at it's highest. Just before the boiling point, I drop the Watts to where they are only holding the temperature, never letting it distill before an hour of heating. The subsequent strips are heated in the preheater, so they get even longer. If there is an optimum time, I don't know what it is.

The higher the temperature, the faster molecules move and the more often they bump into each other, giving them more opportunity to create new molecules. There are no magic temperature steps along the way. That's just made up nonsense to justify a newbie stiller's choice of using a PID in a still rather than having to admit he'd made mistakes after watching another newbie stiller's Youtubes.

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Re: Holding kettle temperature to affect distillate flavour

Post by Birrofilo » Wed Apr 22, 2020 4:46 pm

NZChris wrote:
Wed Apr 22, 2020 1:40 pm
That's just made up nonsense to justify a newbie stiller's choice of using a PID in a still rather than having to admit he'd made mistakes after watching another newbie stiller's Youtubes.
Thanks, very interesting.
I was interested in specific temperatures not to "justify" use of PIDs but because this all reminds me of mashing, in which different temperatures activate, or denaturate, enzymes that create certain chemical reactions. I was wondering whether certain temperatures would create certain esters, while different temperatures would create different esters. Or maybe some enzymes would survive the mash phase when doing whisky (after all there is no boiling when making distillers' beer) and would perform some work later in the pot. (I know mashing doesn't apply to rum, but maybe the molasses contain some enzymes that perform some trick in the kettle, I was making a lot of hypothesis, such as does tomato paste contain enzymes? They would not be denaturated because a sugar wash is always "cold" until it hits the still).

I was probably "overthinking" it. Your strategy of keeping the broth just below boiling temperature for an hour of more seems quite logic, higher heat, more chemical reactions, and if two molecules are destined to marriage, they will find each other and copulate :-)

This was a very interesting and instructive topic to me, and I am taking good note. Many thanks to all.

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Re: Holding kettle temperature to affect distillate flavour

Post by Birrofilo » Wed Apr 22, 2020 5:33 pm

@NZChris

I would like to have some more clarifications:
Do you observe the "butter" aroma in your product, or do you just note esters (meaning the fruity stuff)?
Do you make rum, or whisky, or what else?
Do you use this procedure with all your productions, or only for some specific productions? (I imagine one would not use it for making neutral).

Maybe this gives the "butter" with rum and not with whisky.
Or maybe it gives higher ester content in any case, and "butter" only if there is a high level of diacetyl (diacetyl should be felt by tasting the broth before distilling, especially the hot broth should "reveal" the diacetyl very clearly).

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Re: Holding kettle temperature to affect distillate flavour

Post by NZChris » Wed Apr 22, 2020 7:04 pm

I haven't noticed strong butter in my rum. Maybe it's there, but I'm not recognising it.

My neutrals get stripped through the same Charentaise preheater set up as everything else does, so only the first strip of several gets to start quickly and, if it's a large ferment, one will sit in the preheater overnight.

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Re: Holding kettle temperature to affect distillate flavour

Post by NZChris » Wed Apr 22, 2020 9:55 pm

If you are wanting more esterification, don't restrict yourself to one trick. I very often hold back some fresh wash to add to the low wines from three strips, then hold that charge at just below it's boiling point. Doing a 1.5 brings together necessary acids and precursors at a higher abv than in the stripping runs, so give them heat and time to do their thing.

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Re: Holding kettle temperature to affect distillate flavour

Post by Corsaire » Thu Apr 23, 2020 5:47 am

If I understand it correctly, this combined approach is also how high ester rum is made.
A combination of vinegar infected sugar cane with a molasses based long ferment, with yeast that creates a lot of congeners. Then infected dunder in the retorts, depends on maker. Fresh wash as well, with low wines (tails from a previous run) in the first thumper.
Lime salts and acids to scavenge esters from previous runs, combined with the heads (high wines) of a previous run in the second thumper. This allows a slowish heatup of organic acids in a highly alcoholic environment. I don't think they do temperature rests, just boost every possible way to make esters.

I could be wrong, but this is what I pieced together from all the vague info I found. I'm hoping to try this out this summer when it's warm enough to do big rum ferments.

Some other brainfarts, more on topic:
The butter rum thread heats the wash at the end of fermentation but prior to stilling. Most people think it's diacetyl, made by stressing the yeast and killing them before they have time to consume it.

I've heard references to time under heat in defferent spirits, but have yet to dive deeper into it. I've heard it mentioned referencing gin and whisky.
Todd Leopold of Leopold Brothers installed a three chambered still, an old design that was superceded by the more efficient column still. He claims that he extracts more flavor because the mash stays longer in the still, or gets more time under heat.
Interestingly enough, WIRD of Barbados operates a similar still, and rumor is that it's responsible for the taste of Rockley style rums, which are highly sought after.
Those stills seem like a pain to run though.

As far as distilling goes, I don't know of much more than esterification happening in the still. Maybe Maillard reactions, I need to look those up. And I'm not sure there's target temps to hold, maybe more of a target time to run the whole process, since temps automatically climb during a run. I've never heard of anyone stopping production to 'hold a temp', except for neutral runs to let the column find equilibrium again. Hardly what you're looking for.



And if anyone can find something about how Rhum Le Galion is made I'd appreciate you sharing your findings. From what I gather so far it's just a long fermentation and ran through a column. That's about it. But if you're lucky enough to find their Grand Arome, it's a beast. Too overwhelming on its own, but it can give a nice flavor boost if blended with a more neutral rum.

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Re: Holding kettle temperature to affect distillate flavour

Post by NZChris » Thu Apr 23, 2020 9:42 pm

I'm sure that if you wanted to make something close to Grand Arome, much of what you need to know has been discussed here in various threads. There are a few clues on the net as well. All molasses, 8 days in the fermenter, use vinasse. There is probably more out there if you are prepared to hunt it down. How they use their column would be interesting, but I'm sure something close enough to make you very happy could be made with a thumper.

I do have rum essence that I've made using some of the tricks they are likely to use. It's on oak waiting for some age. It's not something that I would enjoy on ice and is only really useful for blending. That may change with age.

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Re: Holding kettle temperature to affect distillate flavour

Post by Birrofilo » Fri Apr 24, 2020 2:34 pm

Thanks for the answers, keep the information coming! :-)

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Re: Holding kettle temperature to affect distillate flavour

Post by Clamsmasha » Fri Oct 23, 2020 5:50 pm

Bumpity.

I just made my first bourbon. It’s about 65% corn 20% wheat and a everything else in the shed makes up the rest.

I heated up the keg late in the night til’ I’d taken maybe 150ml of heads. At that point I looked et the clock and started to have second thoughts about stilling through to sunrise...so I shut it down, kept the condenser running and hit the sack.

The keg is well insulated and sat for about 12 hours. I didn’t measure the temp when I kicked it in the guts the next day but it must’ve been 50c+.

It has a taste that i would describe as the smelly yellow outside of butter that’s been exposed to air for a while. I like it, seems to fit the corn notes but it’s very obvious and up front.

I *may not have let the ferment go dry before I ran it so the yeast didn’t get to mop up before I killed them.

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Re: Holding kettle temperature to affect distillate flavour

Post by zapata » Fri Oct 23, 2020 6:50 pm

It has a taste that i would describe as the smelly yellow outside of butter that’s been exposed to air for a while.
That sounds like exactly how I would describe butter rum. Well, minus the rum, and plus the ever present oxidized rancid flavor that corn always brings :)

What yeast were you using? I think all the butter rums have been made with bakers, I know mine and the original recipe were. Be interesting to know if it's yeast strain specific now that we know it isn't rum specific.

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Re: Holding kettle temperature to affect distillate flavour

Post by zapata » Fri Oct 23, 2020 7:13 pm

Corsaire wrote:
Thu Apr 23, 2020 5:47 am
Maybe Maillard reactions, I need to look those up.
Definitely malliard reactions happen. Often direct fire stills are said to have more malliard reactions than steam fired because of the higher localized heat, and batch stills more than continuous ones due to time.
I've heard references to time under heat in defferent spirits, but have yet to dive deeper into it.
It's a long running subject over at the Boston Apothecary, including at least 2 articles on chamber stills, but they hit on it all the time from rum to tequila as well. Interestingly enough, I sat down with a cuppa earlier today and read an account including chamber stills from the early 1900s. I was planning to post that up in the history section as soon as I can either chop the pdf or strip the text. I'm absolutely gonna make one, I'm just trying to decide how stupid I want it to be. It's gonna be stupid to run no matter what, so I'm thinking I might as well make it out of cypress as would have been traditional. But I'm keeping my eyes out in the swamps for a good hollow trunk windfall cypress to use rather than coopering it like was traditional. I might end up recreating the missing link between the even more ancient log stills and the chamber still.

Anyway, somewhat on topic, one of Boston Apothecary's theories is that not just time and temperature, but the way the chambers are cycled is relevant. In one direction they push "sweet water" from the spent wash in the bottom chamber to drive the distillation. Likewise the time, heat and acids hydrolize glycosides in the grain (specifically rye here) to yield "rum" oils / rose ketones. But in the other direction fusel alcohols are recycled and exposed to long periods of time and heat with the least volatile acids which would encourage esterification. But not to push those esters into the wash, but by binding them to the largest acids they would be less volatile thus eliminated from the cycle rather than feeding them back up to the final thumper again. Kind of a stripping reactive distillation esterification rather than the kind of esters we usually talk about.

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