Barrel Aged Coffee

I’ve seen a video recently; this video: https://www.youtube.com/watch?v=qIbbJV-grHg

In short, it was inspiring. To be fair, a lot of things in Japan are inspiring but this particular video gave me a lot of motivation. Perhaps it came at a good time. I don’t really have a lot going on, work is slow. It’s a new an exciting concept for me, so lets dive into it.

Barrel Aged Coffee:

You can seemingly go about this in 2 ways, I’ll focus on the latter (#2).

1) Place green (unroasted) coffee beans put them in a humid environment to age over time. The principle revolves around embracing one of the green beans natural disadvantages; the absorption of nearby aromas. Coffee beans should be meticulously shipped in environments they cannot be exposed to other aromas, such as the inside of freight containers, spices, etc. Tea doesn’t really have the same disadvantage? I feel it’s a lot more common for tea to be shipped inside of sealed aluminum bags. I digress, coffee picks up aromas, and this principle introduces selective ones to the dry bean to manipulate the resulting coffee. It’s a neat idea. It seems the favorable container is an oak barrel which has once contained bourbon, wine, etc. This method is interesting, and I will explore it. We will dye cheesecloth with kakishibui (persimmon tannins) to make it antifungal and water repellent. From that we will create a bag and age a few pounds of green coffee beans (probably Indian or Ethiopian) in the urban cultivator. We can set it to practically a rain forest environment , so it should be ideal. Generally if you search ‘barrel aged coffee; this is the result that comes up, which is how I even know about it.

However, that isn’t as interesting to me as…

2) Aging a finished coffee in liquid form. This is the inspiration. How does it taste? There are a lot of reviews about it in Japanese and English with very good comments. There’s supposedly only one place in the world which has it (in Osaka). Although there are a few interviews with the cafe owner about it and he doesn’t seem to be shy about sharing his method, none of those interviews go into very much detail. So I did some digging. What a rabbit hole.

First off, how do you age a liquid coffee? Wont it go stale? Wont it get moldy? Secondly, it costs $750~900 (citing different websites) per cup, why? There is surely a reason. Is it a deterrent to keep stock up? There is apparently only 1 barrel. Are the contents of the barrel a blend in which the average age is 23 years? is 23 years the oldest coffee in the barrel but it has been repeatedly topped up with ‘freshly brewed’ coffee every time liquid comes out? This is the key info. I can’t imagine he would have any left if it wasn’t topped up. The barrel looks like it holds 3L max, and the serving cup is probably 80~100ml (That’s only 30~37 portions). That is $27,000 from 3L of coffee though. That’s not bad business. I want in.

At first it seemed to me there were 2 ways this could be done. It just sort of depends what happens once the process gets started. I’m going to ramble off my thoughts I jotted down on paper.

• I’m pretty sure even refrigerated coffee wont last 23 years. Eventually mold would start to be an issue you have to deal with because of the sugar content of the coffee bean.
• If the coffee was put into the freezer, mold wouldn’t be as much of, or an issue at all. The coffee freezing is now the issue. When coffee freezes the oil comes to the outside of the cube. I’ve done my fair share of frozen espresso icecubes for Q, it’s just all around disappointing. On top of that, if the coffee froze and expanded while the wood constricted, I believe that would damage/crack the barrel over time.
• If the coffee was indeed frozen, it would have to be just to the spigot of the barrel (or else you couldn’t get anything out?) — is the barrel filled only to the spigot with 23 year old frozen coffee and a fresh batch is poured into the hole in the top which skirts around the top of the ice picking up some of the flavors from the ice below? Probably not, especially not for $900. This would be ideal for doing a solera style of coffee though.
• When the barrel comes in and out of the freezer, would the water from the coffee condense on the outside of the barrel? I think it would. So taking it in and out of the freezer several times a day would surely have a pronounced effect. The same sort of effect is how whiskey from Kavalan Solist in Taiwan can get such drastic mature flavors in such little time. That’s osmosis right?

Writing all of that stuff down, it just doesn’t seem that you could pull this off if the coffee froze solid. I asked my wifes help to navigate the Japanese websites which covered this topic and one mentioned that he keeps this coffee at -3 Celsius. That makes sense. It should ideally be -10 if you wanted to prevent any mold from forming at all, but I guess at -3 or -4 it’s pretty slow going. If you were working with clean tools mold wouldn’t be so much of an issue? Darker roasts might help with that too? Anyway some questions were raised:

• What actually makes this flavor unique? Is it simply wood + coffee? Is it the reduction of liquid coffee + wood? Could the same flavor be achieved by just reducing coffee over heat with wood inside? (Doesn’t quite have the same romance)
• New oak will impart sweetness provided the coffee stays liquid, what would it do to ice? (I imagine it doesn’t do much)
• Coffee contains oils, espresso contains more oils than drip coffee (I believe). Do those oils and compounds inside coffee lower its freezing point? The answer to this is a solid ‘probably yes, but not very much’. I did an experiment freezing 4 double espressos in a steaming pitcher and putting it in our walk in freezer at -22. I went in periodically to check the temperature and the liquid was down to -0.3 before ice crystals started forming. Just an observation, could have been an error.
• Assuming what I’ve read on the internet is true, if he cools his coffee to -3 there must be a reason. I think that reason is that if he goes colder his coffee will freeze. I feel it’s more of a limitation than preference. Going ahead with that mindset, how can we lower the freezing temperature of water? Well there are a few ways, not rocket science. Add salt, alcohol, or sugar. There’s probably more you can do, but I know what I know. I guess salty ass ice coffee probably isnt very good. Alcoholic iced coffee might be great, but thats probably not what he’s doing. It must be with sugar. I looked for a calculation.  I found some things that made me realize I’m stupid and instead of going at it myself, I asked a couple of my engineer friends to lend a hand.

To reduce the freezing point of water by adding sugar, you can follow this formula for freezing point depression. I won’t go into what the numbers mean, it’s a wikipedia away. Here’s a link: https://en.wikipedia.org/wiki/Freezing-point_depression

With Sucrose (Disaccharide):

1,86/342*(mass of sugar in grams) = temperature difference in 1L of water

Useful results:

-2 369g of sugar /1L

-3 552g of sugar /1L

-4 735g of sugar /1L

Because glucose is a Monosaccharide (simple sugar) the equation is different. You can use half of it in grams and get the same result. This is especially important when it comes down to honing in on the flavor I want.

That’s where I’m at right now. I think I know what I’m doing. I am waiting for things like the barrels to arrive. I have a very straightforward quest from here on out.

Learn how to make good sweetened iced coffee with ideally more glucose than sucrose? Put that coffee into a barrel and wait a long time. Hopefully something amazing comes from it.