[Desmond007]

Greetings

I'm trying to make an alcohol that tastes like rum.
Just adding toasted oak chips to vodka and let it soak.
Rum has a lot of esters, and i'm trying to understand how these
gets created, during storing of spirits in oak barrels.

I know that oak contain carbolix acids and fatty acids, but how are the esters
created, during storage of these barrels?

Please enlighten me
Thx

[chenbeier]

The ethanol reacts with the acid to form the ester. Its a equilibrium reaction.

[Desmond007]

Fischer esterification?

How important is oxygen in ester formation?

[rolnor]

I think its a very complex mixture but maybe there is some compound in rum that is very caracteristic for the smell and taste of rum?

[chenbeier]

Fischer esterification?

How important is oxygen in ester formation?

The barrel is sealed, so oxygen is not the key for the ester formation.

[Desmond007]

There is indeed oxygen in these barrels. They drill a hole on top of the barrel,
put a cork in it, and takes the cork out on a regular basis.

[Desmond007]

I think its a very complex mixture but maybe there is some compound in rum that is very caracteristic for the smell and taste of rum?

Indeed there is. Same compounds as in pear drops, ripe bananas, some whisky lactones, and butterscotch aromas.

So Isoamyl acetate, Ethyl acetate, ethyl propanoate, ethyl isobutyrate, Phenethyl alcohol, Isoamyl alcohol, beta-damascenone,vanillin.

Esters are the most important ones though.

I do have a mixture now that smells very much like rum, but it's missing those esters (and higher alcohols).
So i was wondering if i can do anything to this liquid, to speed up some kind of ester formation (temperature etc.)?

[chenbeier]

There is indeed oxygen in these barrels. They drill a hole on top of the barrel,
put a cork in it, and takes the cork out on a regular basis.

I thought after putting the alcohol into the barrel, the barrel will be sealed and stored for 10, 12 or more years without touching. After that time it will be opened to get the rum or whisky.
But even then oxygen will come in, the reaction takes place with the acid in wood of the barrel.

[Desmond007]

I think you might be right with the oxygen.

[Borek]

Are you sure there are no esters present already in the spirit poured into the barrels? Oak barrels are used for maturing many kinds of vodka and they definitely taste different, so it is not just oak that matters here.

[Arkcon]

Hi there, we're glad to help anyone, but there are some basic problems with the premise that have been ignored to this point, and this thread will go off the rails if we don't do some work.  Here goes:

Greetings

I'm trying to make an alcohol that tastes like rum.

Rum is distilled from a sugarcane molasses based fermentation.  Some of its flavor profile comes from early fermentation steps.

Just adding toasted oak chips to vodka and let it soak.

That is probably a reasonable way to extract some compounds from toasted oak.  But this is a non-sequitor to your first statement. Toasted oak is used in wine-making, Kentucky bourbon making and many other alcoholic beverages.  Those beverages don't get a rum flavor profile from toasted oak.

In your later posting:

Fischer esterification?

Now that is some good information that you have, that I didn't know before.  So thanks, this has been a problem I couldn't crack until now.  However: from the WIkipedia page:https://en.wikipedia.org/wiki/Fischer%E2%80%93Speier_esterification#Examples_in_alcoholic_beverages

Of course, when compared to sulfuric acid conditions, the acid conditions in a wine are mild, so yield is low (often in tenths or hundredths of a percentage point by volume) and take years for ester to accumulate.

From a reaction with the alcohol and the acids.  But, vodka, as distilled liquor, lacks acids.  And there may be some in the wood, but likely locked in its structure  And again, this is a gradual process.

How important is oxygen in ester formation?

Huh?  Esterification involves reaction with oxygen in the molecule. So which one, and why do you ask.  Not oxygen in the air.

Listen, its kinda cool how Fischer–Speier esterification can add to a beverage's flavr profile, while scavenging some small carboxylic acids, some alcohols -- ethanol and others, into flavorful esters.  There are also complex phenolics and other aromatics extracted from the wood, often called vanillians.  And some ethers and to the aroma profile.  You've removed all of those form your consideration.

But on top of that, there's no mechanism from the esterification -- alcohol with acid, simply by soaking wood.

[Desmond007]

Thanks for helping me out. Means a lot.

Ok, this is what i know so far.

Oxygen is involved in breaking down tannins, that lead to formation of new aromatic compounds.

They DO charr/toast the barrels in the rum industry, and that charring leads to the production of esters. Over charring will destroy this process though.
I guess the carboxylic acids are created in the charring process.

Dunder is used to make some high ester rums. The fermentation creates
different acids like butyric and acetic acids, wich will form esters when reacting with the alcohols.

Vanillin comes from heating the lignin in the wood.

The spirit that goes into the barrels (the heart) smells like rubbing alcohol, and not at all fruity like esters ( I visited a rum destillery last week).

What i dont know, is excatly how the esters gets created in the spirit, because i really dont understand how the Fisher Esterfication works without a catalyst (strong acid), and if it's possible to set this reaction in motion somehow, without a strong catalyst and reflux.

What would i need to do to create esters in my homemade rum?

[Desmond007]

Hands on ester experimentation:

http://homedistiller.org/forum/viewtopic.php?f=1&t=67010

[Arkcon]

Thanks for helping me out. Means a lot.

Ok, this is what i know so far.

We're here to help.

Oxygen is involved in breaking down tannins, that lead to formation of new aromatic compounds.

Non-sequitor.

They DO charr/toast the barrels in the rum industry,

And bourbon.  And winemaking.

and that charring leads to the production of esters.

I don't believe this is true.

Over charring will destroy this process though.

Yes.  Carbon or burnt wood have a different effect.  Thank you for sharing.  This is not pertinent to the topic at hand, and muddles discussions.

I guess the carboxylic acids are created in the charring process.

I doubt that.

Dunder is used to make some high ester rums.

I was unaware that rums are classified by amount of esters.

The fermentation creates
different acids like butyric and acetic acids, wich will form esters when reacting with the alcohols.

Yes.  This is correct.  Esters are made, gradually, in trace amounts.  Nothing in your O.P. mentions gradual or trace.

Vanillin comes from heating the lignin in the wood.

Yup.

The spirit that goes into the barrels (the heart) smells like rubbing alcohol, and not at all fruity like esters ( I visited a rum destillery last week).

It smells like ethanol, which without aroma compounds can be harsh, one of my meads smelled ghastly prior to aging.  It really smelt like gasoline.  It contained none, of course.

What i dont know, is excatly how the esters gets created in the spirit, because i really dont understand how the Fisher Esterfication works without a catalyst (strong acid), and if it's possible to set this reaction in motion somehow, without a strong catalyst and reflux.

Wikipedia is a fine source above.

What would i need to do to create esters in my homemade rum?

Follow a recipe.  Random acts of science don't occasionally lead to random results.  They lead to no results.

[Desmond007]

You Sir, are one helluwa mean lean organic chemistry machine.
So estefirication is possible wirhout a strong acid. It just takes years.
I'll buy some vinegar and put a bit into my rum, and store it for a couple of years.
The scientific stuff will have to wait, until i have my own destillery.