The Cousins Process in High Ester Rums by Richard Seale

[Single Malt Yinzer]

To solve this problem, the brilliant Jamaican chemist HH Cousins developed a process to boost the ester count in rums in a more economical way.

The ‘lees’ in the retort at the end of distillation retains a considerable amount of the acids from the fermentation. Volatile enough to make it to (and concentrate in) the retort, not volatile enough to make it to the rum. The acids are recovered by adding lime (calcium oxide) to the lees to produce the calcium salts of the acids. This concentrated acid mixture after precipitation of calcium sulphate (by adding sulphuric acid) is added to high strength rum (i.e. lots of alcohol) and placed in the high wines retort where the esterification process (alcohol + acid) takes place. The resulting distillate is now supercharged with esters – up to 7,000 – and this distillate is used to ‘top up’ the rums produced in the normal way to reach the levels such as DOK at 1,600.

It appears they use the last retort (thumper to us) to load up with low-volatile acids to produce the esters. This means the acids do not come across to the distillate. Traditional Rum stills will have 1-3 thumpers.

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[Single Malt Yinzer]

Discussion of the Cousins Process (higher level, few details) from 1908:
Report of the Royal Commission on Whiskey and Other Potable Spirits: Cousins Process

[distiller_dresden]

This is cool; what's the definition of "lees" for us, do you think? Like I have a pot still with a thumper, what/where is my 'lees' at/coming from, would my lees by the stuff in my thumper at the end of a run maybe? It would typically maybe be a little higher in alcohol than the pot setback/dunder, it would be higher in sugar as I almost always use a juice/honey/molasses or something to flavor my spirits... Next rum and from now on it's very likely it will be infected dunder (obviously sterilized as it's now been cooked) also, some vinegar, and small amount of rum heads (I add to boost ABV in there and in turn of spirits coming out of thump), but I'm assuming alcohol in the thump is eventually getting out since thump is like a second distillation.

Also, soon I will acquire some sulfuric acid and hit my infected dunder and vinegar and heads with sulfuric immediately before I cook, of course making sure it's 'settled' and there's no acid activity, then placing the hopefully ready to produce esters like a mofo solution into my thumper and cook.

[Single Malt Yinzer]

Lees means the remnants of the yeast from fermentation. For beer folk it's the trub (minus hops). Some people will stir up their wash before they put it in the still to get the lees in suspension. The yeast has esters and ester precursors (namely fatty acids). Boiling yeast breaks down the cell walls and allows the esters and other chemical constituents to interact with the wash. Not everyone likes to do that, and most people find spirits made without lees tend to have a cleaner taste. It's open to debate as other factors apply.

[distiller_dresden]

Ahhhh. Yes, I've only been distilling for 5 months, since Jan. All I've read and learned and been told is to use as 'clean' or clear a wash as possible and that yeast will affect flavor...

So the yeast trub in the wash will create more esters if they're in there when I'm cooking, but there is also the very real possibility that they create an off flavor in the spirit?

[Single Malt Yinzer]

Pretty much that's the trade off. You can vary how much lees you stir up but it's not likely to be an easily repeatable process. At first I did the clean wash now I'm most/all the lees. I found it to add tails so watch your cuts. I've gone way to deep into the tails to chase aromas but the flavor suffered.

[distiller_dresden]

What if I didn't put much of the lees into my pot, but I did put lees into my thumper along with infected dunder and a touch of vinegar, like an ounce, along with rum feints and wash? Would that have a high chance of producing some really good esters as well as avoiding the problem of yeast making off flavors from being in the cooking wash in my pot?

[Pikey]

Interesting that bit about using CaO to gather the acids and then getting it to release it in the product !

Anyone know how that works -?

der wo ?

[OtisT]

So if I am reading this process correctly, the article says to pull the “lees” from their last thumper? I find that interesting and different than all the other dunder experiments I have done to date, where my source for acid has been dunder from the strip run and/or primary boiler when I am thumping. If my interpretation of what that article suggests is correct, then I have some new experiments to run.

Question on this: If the acids make it to the retort but not to the product collected, as the article suggests, how/why did the acids make it through the previous distillation process from the primary boiler Into the retort (thumper) in the first place?

That bit about using lime is very interesting. I’ve been doing something similar to this , mixing dunder with feints and adding that mix to the spirit charge. Recently I have been playing with acids (as a catalyst) in this mix, but had not tried using lime in the mix first. Regardless of where the lees come from, I will have to do some testing with lime in the mix.

Otis

[Single Malt Yinzer]

Dresden - that's what the Cousin's method is. Put all the funky stuff in the last thumper in line (labeled high wines) and let'er rip. If you only have one thumper do it in there.

doubleThumperRumStill.png

[der wo]

Thanks SMY!

As always some details are missing or perhaps wrong. Here how I think what they mean. No guarantee that everything is right:

"Lees" in this case means not the yeast of the fermenter, but the liquids in the retorts after a run. They contain fusel oils, acids and at least in the second retort is also ethanol. But I think here they mean the first retort. Normally the lees can be reused in the wash, but if you really want to boost esters, to concentrate the acids is a great idea. Simply boiling the water away doesn't work, because the acids are a bit volatile too. So they add lime to neutralize the acidity, and now it's possible to boil it down. Salts will fall out. And those salts are added to the "high wines" (the early tails of the last run) into the second retort. Not the salts recovered from one run, but from many runs! This is the trick. With this method you can collect acids from many runs and add it to one special high ester run. Then you have ten nice normal Rums and one ester monster for blending.
What I don't understand is the detail with the calcium sulphate. Of course when using the salts they have to add an acid and a catalyst, both is sulphuric acid. But why does calcium sulphate fall out? Or why it is important that it falls out? Whatever, it's a minor important detail I think.

My opinion is, that there are many ways to skin the cat. It's not difficult to produce many esters. But also with the Cousins process the acids have to be produced somewhere in the process. And this reduces the alcohol yield like with any other method. But because getting esters always costs alcohol, so they are not for free, it's bad to waste many of them by dumping the lees. But who dumps the lees? Normally they get into the next wash. This is much easier than Cousins method and this is the normal way the distilleries do. So the only advantage of the Cousins process is that you can take out acids from a few runs and concentrate them into one special run.


How to adapt this for homedistillers?
Simply every time when it's possible to collect Rum distillate without alcohol (for example at the end of stripping or after the tails of a spirit run), collect distillate into a seperate container. Then add lime to pH 7. Then boil it down as far as possible.

[Single Malt Yinzer]

So if I am reading this process correctly, the article says to pull the “lees” from their last thumper? I find that interesting and different than all the other dunder experiments I have done to date, where my source for acid has been dunder from the strip run and/or primary boiler when I am thumping. If my interpretation of what that article suggests is correct, then I have some new experiments to run.

Yup. All the funk goes in the thump. (It's not a perfect rhyme but it's not like you're paying for it.)

Question on this: If the acids make it to the retort but not to the product collected, as the article suggests, how/why did the acids make it through the previous distillation process from the primary boiler Into the retort (thumper) in the first place?

What Cousins did was reduce the volatility/menuscibility of the acids with the lime. I don't understand the chemistry so I can't explain it. They are catalysts and do not get used up and their boiling point is too high to come over into the distillate - or at least not enough to be meaningful. They sit there to be used over and over. Great for making one rum over and over, then blending it with something else to make the specific expression - high, medium or low funk.

Edit: Rereading the method and Der Wo's post it's the stillage from the pot that is brought over to the last thumper. Since the acids were not volatile in the initial run they stay in the stillage no matter how many times you run it. Thanks Der Wo for the clarification on the difference in terminology.

[der wo]

that's what the Cousin's method is. Put all the funky stuff in the last thumper in line (labeled high wines) and let'er rip.

I think it's about adding concentrated carboxylic acids where the highest concentration of fusel alcohols is.

[distiller_dresden]

Love the diagram! I didn't know they're using 3 thumpers, that's awesome, and crazy (good crazy)! Otis, I can't WAIT to see you doing experiments with this, I think this experiment sewn into your existing line of thought on sulfuric acids and such, you are just the king of science and rum to obtain and utilize 2 or 3 thumpers to get things rolling with an experiment.

I can't even imagine how long a cook would take me with 3 thumpers. I'm at 5-6 hours now with my 1 gallon thumper and a 5 gallon pot. I imagine each thumper would add about 1.5-2 hours. 3 thumpers could conceivably be an 8-10 hour cook for 5 gallons; f'ing wow. Just wow.

The rum I'm fermenting now, no doubt, the thumper is getting yeast trub, wash, an ounce of vinegar, infected dunder, and rum feints (I've been saving them from my last rum rums about 2 months ago!). Gonna be very interesting now, I'm even MORE excited. My infected dunder is looking sexy since I added parmesan cheese, swiss cheese, and fresh live active yogurt from a local dairy. Smelling pineapple, that weird 'brown sugar gone Michael Jackson bad' smell, something like soy sauce, and something maybe like early rotting pears, with a touch of sour milk.

EDIT - so the lees is the thumper contents after the run, then?

[Single Malt Yinzer]

I kinda see this revelation as a pretty big leap in understanding of Rum production as well as high ester spirits in general. It brings together a lot of what Der Wo and OtisT and others have been working on. We now have many different ways of creating high ester spirits. This is definitely going into the Wiki.

[der wo]

Question on this: If the acids make it to the retort but not to the product collected, as the article suggests, how/why did the acids make it through the previous distillation process from the primary boiler Into the retort (thumper) in the first place?

The acids are volatile, but not as much as for example ethanol or esters. Not all of them will make it into the retorts, but a few will.

BTW, we loose with this method the higher alcohols of the lees. When we boil the lees with the lime down to get the acids, we boil off the higher alcohols. This is, what I don't like in this method.

[Pikey]

.....BTW, we loose with this method the higher alcohols of the lees. When we boil the lees with the lime down to get the acids, we boil off the higher alcohols. This is, what I don't like in this method.

I'm wondering if many of the Calcium compound so formed are insoluble in water Like Calcium Carbonate and Calcium Stearate for example ?

If so, it could be a convenient way of isolating them by simple fitration ?

[der wo]

To be insoluble and to fall out are two different things. Only if something is difficult to solve doesn't mean it will fall out immediately and to a large degree.

At least calciumacetate (the salt from lime and acetic acid) is easy soluble in water.

Perhaps boiling it down to a certain degree, seal it and then let grow crystals? I mean:
?Rum crystals?

[der wo]

BTW, this "switching on and off" of the volatility of fatty acids by pH control is also used in Arroyos method of clarification of molasses wash before fermentation:
He heats the wash up. This causes ash and gums to fall out and "amelioration or evaporating of foul odors". But because he doesn't want the fatty acids to evaporate, before heating he adds lime to rise the pH. And when the wash is clarified and has cooled down, he adds acid to drop the pH again to a good level for the yeast and for esterification.

BTW2, you can test this method easily: Fill a small glass half with vinegar and add much of a strong base like lime or caustic soda. With mild bases like soda or natron it will work probably too, but slower. You will notice that the vinegar smell has gone.
If this doesn't convince you, perhaps the second part of the experiment does: Now with a strong and odorless acid like sulphuric acid you can wake the smell up again. But this is a bit dangerous. It will heat up and fizz very strongly. Wear gloves, glasses...

[Shine0n]

By the diagram it states low wines 50/50 and high wines 75/25, does that mean what? wash plus low and high wines, trub/lees?
I get confused about some of this, I now have a double retort system and have only began to scratch the surface. I get what I would call a high ester rum, without having a lab and someone who knows what the hell their doing I cannot legally call it such.

I'm reading and watching these threads with much interest to get a larger understanding and I'm so glad der wo and Otis have been doing all this foot work for us (HD) so we further understand some of these processes and their uses.

I will further my own experiments but settle down on just a few recipes, this vinegar has my attention now and may apply it to one of my processes to further my deep hole obsession with rum.

Just for the record, I do not want to replicate a commercial rum but come up with and make a unique rum I can be proud of and possibly...

[NZChris]

You can download the report here:

(Link deleted)

See page 491

[der wo]

By the diagram it states low wines 50/50 and high wines 75/25, does that mean what? wash plus low and high wines, trub/lees?

50/50 means 50%abv and 75/25 means 75%abv. At least this would make sense, because this matches to informations of other double retorts setups. To dilute the feints 50/50 and 75/25 with water or dunder doesn't make sense, at least from their perspective, not necessarily from our.

NZChris, the link doesn't work, at least for me.

[NZChris]

By the diagram it states low wines 50/50 and high wines 75/25, does that mean what? wash plus low and high wines, trub/lees?
I get confused about some of this, I now have a double retort system and have only began to scratch the surface. I get what I would call a high ester rum, without having a lab and someone who knows what the hell their doing I cannot legally call it such.

What they are calling High Wines, we call heads, so 75/25 is heads/water.

What they are calling Low Wines, we call tails, so 50/50 is tails/water, however, the first retort may also contain some wash, dunder, heads, whatever the distiller desires.

[der wo]

What they are calling High Wines, we call heads, so 75/25 is heads/water.

What they are calling Low Wines, we call tails, so 50/50 is tails/water, however, the first retort may also contain some wash, dunder, heads, whatever the distiller desires.

Where do you know?

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the beer is only 6-9% alcohol, while the low wines are approximately 30% and the high
approximately 75% -but are still less concentrated than the desired finished product. Heat is applied to the pot still, causing evaporation of the beer. Upon hitting the retort filled with cooler low wines, the water in the beer condenses; the heat from this condensation is enough to evaporate much of the ethanol in the mixture. This process of condensation and evaporation is repeated in the high wine retort. Finally, this vapor, now highly concentrated in ethanol, moves to the condenser, is cooled to the point of condensation, and is collected. The initial condensate is collected as headings and typically discarded. The first fraction, at about 90% ethanol, is collected to be aged into rum. As the ethanol begins to be exhausted, second and third fractions are collected to replenish the high and low wine retorts, respectively (Buglass 2011).

[NZChris]

What they are calling High Wines, we call heads, so 75/25 is heads/water.

What they are calling Low Wines, we call tails, so 50/50 is tails/water, however, the first retort may also contain some wash, dunder, heads, whatever the distiller desires.

Where do you know?

The meanings of 'Low Wines', Seconds" and 'High Wines' that Jamaicans use are clear in the flow diagram that Single Malt Yinzer already posted on this thread.

[WeegieDistiller]

Der Woo what you quote goes with what Richard Seale mentioned to me when recently out in Barbados.

The tails themselves have cuts made to them during the run, collect the tails down to about 50-60% (depending on preference) which is classed as your high wines and the remaining tails would be your low wines.

Using the double retort yields quite a high final %abv around the low to mid 80s which is why the tails start at a high percentage as well.

[der wo]

Yes, the diagram looks like in the second retorts are the heads. But then the second retort would have to be much smaller, because the heads fraction is much smaller than the tails fraction. When you look at the pics of Hampden, Appleton, Worthy Park and others, the retorts are large and both have the same volume.
Yes, I also wonder where the heads go. I don't belive that they are simply tossed away. Perhaps they go into the second retort. But then together with the early tails. Definetely not with water or dunder. Because then it wasn't possible to get a Rum new make with 85% (or higher).

This diagram is a sketch from a homedistiller. Harry, from the artisan forum. I don't know, where he got his information.

[kiwi Bruce]

Let me see if I'm getting this...
Step 1, Run a series of regular rum washes, say ten runs.
2, Collect the lees from the pot still (Beer run) of each of there distillations. (these are full of the fatty acids that make esters, but didn't distill over)
3, Add lime (Calcium hydroxide) which turn the FA's into salts that are no longer volatile.
4, Boil the lees/salt solution to reduce it's volume down to a manageable volume (say 1/10th)
5, Add this concentrated "liquid" to a thumper with a high ABV spirit wash and re-acidify this with Sulfuric acid to bring the total pH to around 3 (did I read this here? pH 3) This will make the FA's volatile again, and makes them available to the sulfuric acid to catalysis them into esters.
6, Collect this Super High Ester Rum and use it to blend with regular Low ester Rum to produce a product that has a consistent High Ester content, and is reproducible, every time.
This this correct?

[der wo]

You must have a clear liquid to boil it down. So either the backset of the spirit run or the liquid in the thumper or after stripping collect further distillate with zero abv.

[kiwi Bruce]

You must have a clear liquid to boil it down.

OK please explain why?