Using reflux to encourage Fischer Esterification

[Kegg_jam]

..off topic..

Glad to see you are posting again der wo

[zapata]

Chris, I looked and don't see a ref to diethyl ether forming an azeotrope with ethanol. One ref specifically says no:
http://www.ddbst.com/en/EED/AZD/AZD%20E ... 0ether.php" onclick="window.open(this.href);return false;" rel="nofollow
I also didnt see an azeo with any congener I recognized.

It is synthesized from ethanol and sulphiric acid, but the synths I looked up had massive amounts of acid. Roughly a 2:1 h2so4:ethanol by weight and are carried out in a voilent bumping boil at 130-150*C. Maybe some is formed at lower temperature and lower concentrations, but the amounts we are proposing are not far off from what commercial folks already do for treating washes or clarifying molasses, so they would be generating comparable amounts as well. Absent some crazy high bp azeo I think we just dont have to worry about it, it boils at a mere 34*C.

But it is probably a good warning for anyone thinking of using massive amounts of concentrated acid. Aside from the silliness, ether is no joke in terms of flamability, pooling vapors and explosive power.

[NZChris]

In that case, it shouldn't be a problem. I might try an experimental run to see if my nose can pick it up. Back in the 18th Century, when some were putting H2SO4 in gin stills, they might not have bothered with a foreshot. If so, they might have collected some, making the gin sweeter.

[Single Malt Yinzer]

One thing I have been reading about is boiling yeast. I'm starting to believe that part of what is happening is due to chemicals from the interior of the yeast cells interacting with the wash. This would increase the fatty acids available for esterification. Up to this point those fatty acids would be stuck inside the cell walls. Most rum literature states a preference for longer chain fatty acids for flavor. I found some references to boiling breaking down longer chain fatty acids to shorter chains.

Some thing I found when I googled "boiling yeast":

When you boil things expand and same is the case with the contents of the cell and the plasma membrane. Eventually they will burst and release all its contents.

Boiling will denature the proteins within the cell, and this will quickly stop all functions inside of the cell. The high temperature will also probably damage the cell wall of the yeast cell, and thus the cell also might rupture as a result.

Since yeast have a strong cell wall, they can still remain intact but all the important ions, minerals and small molecules will ooze out through the cell wall.

[zapata]

Most commercial rums probably all the yeast ends up first in the boiler, few have ferments sitting around long enough to clear. Then any lees will end up in the muck pit. I suspect the yeast are in fact chemical feedstock for Esters, as well as biological food for the microbes.

But if what you're getting at is that boiling breaks down the fatty acid chains into less desirable shorter chains, would it prove useful to feed the muck pit with unboiled Lee's? Autolysed lees maybe?

[AlChemE]

I'm looking to make some gin here soon from either a sugar wash or simple pale malt recipe. So if adding acid will increase esterification, I'd suspect that adding a base to the boiler (sodium carbonate?) during my stripping run would have the opposite effect and likely produce a more neutral product (before adding botanicals)?

[OtisT]

I'm looking to make some gin here soon from either a sugar wash or simple pale malt recipe. So if adding acid will increase esterification, I'd suspect that adding a base to the boiler (sodium carbonate?) during my stripping run would have the opposite effect and likely produce a more neutral product (before adding botanicals)?

That is my understanding of it.

Check out the thread titled “Baking Soda” started back in 2008. http://homedistiller.org/forum/viewtopi ... =15&t=5753

Otis

[Single Malt Yinzer]

So I forgot my Arroyo. He covered this in his 1945 Heavy Rum patent: https://patents.google.com/patent/US2386924A/en" onclick="window.open(this.href);return false;" rel="nofollow

the kettle of the batch still is charged, and the contents are carefully brought to gentle ebullition. This gentle boiling should be maintained during the whole distillation period, by careful control of the steam admitted to the coils of the kettle. At the beginning of the evaporation, the ascending alcoholic vapors are totally refluxed back to the column, for a time which is determined largely by the particular characteristics which it is desired to impart to the end product: it has been found that l to 2 hours of refluxing is appropriate in most cases.

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SMY, The reason that concentrated H2SO4 is a good catalyst is that it is a "drying acid" i.e. it is very hygroscopic. Remember that Fischer esterification is a reversible reaction. By sequestering H2O from the reaction site, you encourage the forward reaction and discourage the reverse reaction. Not that other acids or dilute H2SO4 won't work, but they will be less efficient.

I've been thinking about this ever since you posted it. There's a lot to this for storage. It actually creates a conundrum for me. I've been seeing some craft distillers going to a low barrel entry - 100 proof or less - to reduce some of the tannins coming out of the wood. Typical barrel entry is ~120 proof. The reduced proof would reduce ester formation due to the extra water. It may reduce the speed of the pH change by a bit as it's pulling fewer tannins. So when thinking of storage, where should a finished spirit sit for max esterification or reduce barrel acidification? Seemingly can't do both? Maybe over oak at a lower proof? All these things probably should be experimented with.

[zapata]

While it doesnt directly address your question, 2 other things that have always stood out to me about that Arroyo process. In the molasses treatment step, ph is raised with lime for clarification, and then brought back down with strong sulphuric acid. And then a reflux period is specified for building esters, not just stacking the fractions in the still. No mention is made that sulphuric is necessary, but it is specified from the beginning. It's a pretty specific and detailed protocol that should probably be taken as a whole. Most home distillers are not using sulphuric for setting initial ferment ph(citric being far more common), and many home rum makers aren't using any/much acid because they aren't doing the alkalized clearing step.

Maybe over oak at a lower proof? All these things probably should be experimented with.

My little reflux whiskey "ageing" experiment is pretty much right up that alley. It started as a white pot stilled UJ style sour corn sugar head, made with pretty wide cuts more on the tails side than heads. It was definitely over oaked via the nuclear method. Not terrible oak tea, but definite tannic bite and toothpick notes present.
And it was nuked at a pretty low "barrel" proof around 55%.

It's related, but pretty far OT for this thread since it deals at least as much with mellowing oak flavors as much as esterifying the tailsy cut, so I'll start a new thread soon as I get more results. But so far it's been refluxed for over 24 hours with some areation in between reflux sessions and is definitely an improvement over the non-refluxed control. I plan to give it another 48 hrs under reflux before really judging it.

[vqstatesman]

Longer heatup times will cause more esterfication also. Just because you can get from ambient to 170F in 45 minutes, doesn't mean you should. You're not saving power either way just getting more flavor.

And if you extend the time in the boiler while heating, there are more components at play than if refluxing in the column.

If your norm is to heatup as fast as you can, try cutting it back and taking 50% longer. You'll get a lot more flavors.

Just getting back into my stilling time of year and looking for alternative ways to increase my rum and bourbon flavour outputs...

I typically have a heat up time of 1.5 hrs. Ran a batch last weekend (Rum) with a slow heat up time approx 2.5 - 3hrs. OMG I was blown away by the increase in flavour of my white dog while doing cuts. MASSIVE flavour increase!!! MASSIVE!!!

For the record I didn't hold in full reflux. Just a slow warm up and slow take off of fores. Up the power and run as normal, take of 88 ABV on 4 plated column.

[OtisT]

Just getting back into my stilling time of year and looking for alternative ways to increase my rum and bourbon flavour outputs...

I typically have a heat up time of 1.5 hrs. Ran a batch last weekend (Rum) with a slow heat up time approx 2.5 - 3hrs. OMG I was blown away by the increase in flavour of my white dog while doing cuts. MASSIVE flavour increase!!! MASSIVE!!!

For the record I didn't hold in full reflux. Just a slow warm up and slow take off of fores. Up the power and run as normal, take of 88 ABV on 4 plated column.

Promising observation, and very timely for me. I am planning to do a test of this very process tomorrow with two strips of honey bear bourbon. I am running one on a very long warmup and one fast. I'm keeping both in their cut jars to see if I notice a difference between the two and if so where in the run they occur. I'm documenting the test in my thread "High Ester Bourbon."

So if you don't mind sharing, I have a few questions about what you noticed and how you did it.

Was your long heat up run a spirit run or did you do this in a single run?

Did you notice the difference in individual cut jars, or on your blended cut?

Was the difference you noted between your old rum and new in the flavor or the smell or both?

Can you put a description or feeling to the difference you are detecting?

Thanks. Otis

[vqstatesman]

Otis I think we might be travelling some similar journeys at the moment. I have been watching your threat about infected dunder in your bourbon.

I have a bain marie setup with agitator and 4 plate column. Always do single runs for everything, take off ABV starts at 90 and I allow it to drop into mid 80s by the end of the run. Being a plated column there is some reflux to get the ABV where I want it but not a huge amount.

FYI I mash, ferment and distill in the one vessel. So when doing bourbons etc everything is done on the grain.

My last run with the long warm up (twice as long as normal) caused the spirit to have stronger flavours right across the run. However I felt the hearts was were the flavour seemed to be amplified the most. The late heads and early tails seemed the flavour was not quite as amplified but still stronger than usual. Overall the flavours were much the same just increased in intensity. I'm rather poor with using words to describe flavour profile however I'm certain there was a more buttery and floral flavours. Also the white spirit did feel more sharp right through the hearts.

Smell of the entire run and most noticeable in the hearts was increasingly amplified. After airing for a week I took a sniff and the smell was overwhelmingly strong (90 ABV).

I typically air my spirit for a week and then dilute samples for my cuts. I normally do cuts by flavour only, not smell. Typically I sample my cuts at around 45ABV. With the last run I had to dilute my cut samples down to around 35 ABV to be able to accurately make the cuts.

Can't wait to age this on oak! Ohh and try the same technique with my bourbons later in the year.

[vqstatesman]

Just thought I'd add that I'm currently in my garage running another batch up Rum. I let it take 2.5 hrs to warm up

[Single Malt Yinzer]

I'm still researching this but it appears that beyond Fischer Esterificaton, copper in the still may also catalyze ester formation. viewtopic.php?f=1&t=69935

[OtisT]

I normally do cuts by flavour only, not smell. Typically I sample my cuts at around 45ABV. With the last run I had to dilute my cut samples down to around 35 ABV to be able to accurately make the cuts.

I find this very interesting and my hats off to you. I’m a nose guy, but I am slowly working my way into more taste based decisions. I’m the same on ABVs, finding that just under 40 offers a great view into the spirit. I started by doing cuts by nose only. Sure I tasted too, but I could not make sense ( no pun intended) of the flavors. The last 6-9 months I have been trying to learn cuts by taste and find my cuts are a bit narrower when I do. I usually exclude one or two more heads/hearts transition jars than I would have by smell alone, and my young drinks are the better for it. I actually like some aspects of the smell of heads, so tasting helps temper my inner desire keep more heads in the cut. There is just something about that sweet fruit smell I like. Bottoms usually come out the same or close by one jar.

Some day I’d love to hang out and do cuts with some taste based cutters so I can taste what folks are describing. So if you don’t mind sharing, describe some of the dominant tastes you can identify in your spirits in the heads transition, hearts, and tails transition? Or maybe you taste for exclusion, in which case what tastes are you looking for to exclude? I taste a lot, but have a hard time putting a name to individual tastes.

Thanks, Otis

[MDH]

I'm still researching this but it appears that beyond Fischer Esterificaton, copper in the still may also catalyze ester formation. viewtopic.php?f=1&t=69935

All the transition metal oxides are known catalysts in organic chemistry, e.g. MnO2, Cu₂(OH)₃Cl, etc. Copper oxides catalyze oxidation at high temps. Oxygen is involved in esterification.

The effect of copper's catalytic properties has been done to death in distilling; not the least worth mentioning is the fact that Catalyzers are in almost every modern still being made in Germany.

Platinum and platinum compounds do it as well. It is already well known in Vodka production.

[Single Malt Yinzer]

Thank you MDH. A quick google got me this: https://en.wikipedia.org/wiki/Surface_p ... tal_oxides" onclick="window.open(this.href);return false;" rel="nofollow

Transition metal oxides are compounds composed of oxygen atoms bound to transition metals. They are commonly utilized for their catalytic activity and semiconductive properties.

[OtisT]

I was very excited to perform my own test of Fischer Esterification and report the results. I found one likely big flaw in my test process that make my results questionable, but I will cover what that issue was and hopefully will be able to retest in the future to see how big of a factor it was.

The test: Two strips, back to back, from the same ferment. One was a quick strip, as fast as my product condenser would allow. The second strip started with over an hour of warmup (140-150 F) and over an hour of boiling under full reflux before I turned off reflux and stripped it fast.

The ferment is Honey Bear Bourbon with the grains.

I had read that copper was a catalyst for some esterfication. I have a copper column and SS Boiler. I am not sure if the copper column would be in the right place as a catalyst, especially during warmup, so I added some copper bits as a catalyst to the bottom of my stainless steel boiler just to be safe.

Potential problem. My first strip was the long run. I used Clear ferment siphoned off the top. My second, fast, strip used ferment that was half clear while the other half had been squeezed from the grains, so it was cloudy. In retrospect I should have squeezed all my ferment first then either used cloudy in both strips or let it settle and use clear beer for both.

Collection. I collected four samples from each run for testing, at 20%, 30%, 40%, and 60% through the run. I sealed those jars off the still and only opened them just prior to this first sampling of the results. I will compare these two again after they have aired for a couple of days.

Comparison after only 1 hour of airing.

In summary, the two products collected are quite different from each other. I would consider making a cut using the slow strip but I would not with the fast strip. I enjoyed smelling/tasting the slow strip but not the fast.

The Fast strip is characterized by a strong sourish/offensive bottoms smell that permeates all jars. I would consider this normal for a fast strip of bourbon like this. I also described the fast strip jars as “sharper” than the slow strip, an intense bite when you smell it. The offensive bottoms and sharpness made detecting anything else impossible at this stage. Maybe after some more airing? Even the first jar was described as having sour/ flat notes to it and none of the bright/sweet notes I normally associate with a heads/Hart transition jar.

The Slow strip was entirely different.
I could detect bottoms in the slow strip, but only in the last three jars and it was not sour offensive bottoms but a warmish pleasant bottom that allows me to smell other things around it. It’s what I typically associate with my young base Bourbon. I did not detect bottoms in the first two jars. In the 30% jar I got a pleasant blend of sweet, almost vanilla like and barely a hint of pleasant bottoms. The first (20% ) jar was described as creamy with spice. (That’s odd. Not terms I usually find myself using to describe my Bourbon, especially this close to the heads.).

So that is it for notes on sampling my fresh strip. I will let these air a few days and report how these change with some time.

Otis

[Single Malt Yinzer]

Thanks for sharing Otis. Your attention to detail is awesome. It's cool that you noticed such a difference with the same wash.