From The Bruery:
We've recently been dissecting the laborious process of making sour barrel aged beers and the process of keeping them happy. Now that we've looked at the brewing and lab work required for these beers, it's time to address cellaring and barrel aging.
After these beers are brewed, they are racked into barrels that fall under the scrupulous watch of our Wood Cellarman Alex Kennedy. These barrels are stored mainly in two off-site warehouses and taken back and forth to the brewery building as needed for filling, emptying, and hugging. Alex and our team spend many hours babysitting these barrels to make sure they (and their precious cargo) are content.
When we brew batches of sour beer for aging, we won't see them again for many months, or even years. On top of that, a percentage of beer evaporates from these barrels each year, so we actually end up with less beer than when we started. This means we're making beer that is not being sold immediately, some of which is very moody, expensive and vanishing into the air!
It takes building relationships with wineries and coopers to get these barrels, not to mention some funds to afford storage space for them. And since we love to get crazy with ingredients at times, getting large quantities of fruit (including weird ones) to add to these beers can certainly tally up some costs.
But we believe this is all worth it to make the beer we love. Lots of you had questions about our sour barrel aged beer, so Alex addressed the cellaring & aging side of things in this post.
What kind of special care do the barrels require?
We age most of our sour beer in used red wine barrels and since we only want a small amount of barrel character seeping into those beers, we soak them by filling them with 180º F water and waiting until the wood expands and they stop leaking. This should also remove any tartrate, an organic compound that may be left behind from the wine. This is a necessary step as barrels are not glued together -- they are made of arched planks of wood called staves that are pressed together and held in place by metal rings.
I'm also constantly on the look out for bungs that may have popped out due to the pressure inside the barrels. Fortunately, they generally pop for a couple simple reasons:
- the liquids inside are still producing massive amounts of CO2, which happens during the first month or two after filling the barrel
- there was an increase in temperature in the warehouse
- the physical agitation from moving the barrels around caused some more CO2 to come out of the barrel
Earthquakes I have to try not to think about because if the barrels fall I will likely be crushed!
When sampling or adding ingredients to a sour barrel, do special steps have to be taken to avoid disturbing the contents?
We sample the beer by drilling a hole in the head and then plugging it with a stainless steel nail. This allows us to remove small amounts of beer without disturbing the pellicle (the thin film inside the barrel that sits on top of liquid), much like a wine thief would.
Unfortunately we don't have a good method of adding fruit without disturbing the contents. And when removing any significant amount of beer, like we might need to for a special pin or cask, we fill the headspace of the barrel with CO2 to try and avoid oxidation. 
What steps do we take to avoid contamination of non sours barrels?
We use entirely separate equipment for sour and non-sour beers. That means we have separate hoses, gaskets, valves, and even separate bottling lines inside the brewery in our packaging area.
How much fruit per gallon is used to make beers like Sans Pagaie?
The amount of fruit we add to a beer can vary a lot depending on the fruit and how fruity we want it to turn out. In fruit forward beers like Sans Pagaie, our sour blonde with cherries, we usually have about 42 pounds of fruit in one wine barrel. Usually these barrels contain 225 liters, which translates to almost 60 gallons, so that's very roughly 2/3 a pound of fruit per gallon.
We do have some barrels in the 228L, 265L, 280L, and 500L sizes as well, and with a stronger flavored fruit like kumquats, we only had to use 5.3 pounds of fruit per wine barrel. So for Sour in the Rye with Kumquats, the amount of fruit per gallon is very different.
On beers where we want the fruit to be more of a subtle, background character, like with Bottleworks XII, we only used about 1/10 as much fruit as we did for Sans Pagaie.
Is fruit added fresh, whole, puréed, dried?
We have tried adding freeze-dried fruit, air-dried fruit, fresh fruit that we puréed and store bought pre-made purées. We don't add any of it whole, but a few times it was just smashed up and jammed in there. We've found that the puréed form delivers flavor more efficiently while clogging up our equipment much less.
What kinds of precautions are taken when adding fruit or other ingredients into the barrels?
We purge the headspace before adding anything and we try to do it as sanitarily as possible by using isopropyl alcohol liberally, but it's pretty hard when working with something as porous as wood.
Do you ferment first with yeast then sour with bugs or do you do it all at the same time?
This depends on the beer. Generally, when brewing sour barrel aged beers, instead of completing fermentation in steel tanks we rack the beer into giant wooden puncheons that have bugs already in them and it ferments with yeast in there. We can then add bugs when those beers are moved into smaller barrels where they can finish souring and aging.
Now all of that said, sometimes a barrel just might go bad. But it's a risk we are willing to take to make the beer we are passionate about creating. Next up, sour barrel aged beer and the joys of packaging it!
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