In the beginning of October I put 40 gallons of 18 month old "Méthode Lambic" beer on to 80 lbs of wild blackcap raspberries. These berries were foraged from the woods of the Driftless region by the crew at Forager Brewing. I can only imagine the dedication that is required to harvest 80 lbs of these tiny little berries.
In preparation for making this beer, I had to figure out how to fruit it. With only 80 lbs of fruit, I knew I needed a ~50 gallon vessel for fruiting. Using a modified barrel would be a perfect vessel, but presented a set of its own hurdles. The biggest of which were 1.) how to empty the beer when it's finished, and 2.) how to prevent too much oxygen exposure.
The fruit screen pictured in the previous post was my answer to issue #1, and it worked perfectly. I was a bit nervous about how much these small berries would disintegrate during secondary fermentation.
I attached an in-line strainer to make sure the beer came out clean and to get an idea of what would make it through the fruit sieve. As hoped, the fruit bed itself becomes a strain and captures most all of the fine particulates.
I was able to completely empty the barrel without the strainer clogging, and this was all that made it through. Just a collection of raspberry seeds. If you've ever emptied beer off fruit, you know this is pretty incredible. The fruit bed was completely dry, which means I probably captured a good 5-10% more beer than I would have otherwise, and with a beer this expensive, that is going to pay off immediately. We have made these available through Stainless Brewing and can be ordered here:
Issue #2, oxygen exposure. This was my biggest fear, and the aspect beer people voiced concern about the most. I know punch downs are common in the wine world and O2 exposure is as much of a concern for them as it is us. I also believe the wine world has much more experience when it comes to to fruit and there are lessons that the beer world can learn from them, even if they are scary at first.
So, even though I was afraid I'd ruin the beer, I trusted the concept. During the secondary fermentation, I punched down the cap twice daily. It was a very gratifying experience. I did CO2 blanket the top prior to fermentation starting, and at one point after fermentation even push CO2 through the drain port.
But maybe most importantly, after fermentation was finished and I was done with my daily punch down regimine, I put a sheet of plastic over the top of the barrel and used extra barrel hoops to secure it to the sides of the barrel.
While I know gas was able to escape, I was very encouraged to see water droplets form on the top of the plastic sheet inside the barrel. I believe this means the gas mixture inside the barrel was not exchanging with the air outside the barrel at any significant rate. More to the point, the CO2 was staying inside the barrel.
Look at that color! The aroma and flavor are equally as amazing. I am 100% sold on punch-downs as well as black-cap raspberries. It was an incredibly expensive and laborious process, but the resulting beer is mind blowing.
Thank you again to Forager Brewing for this collaboration experience and the idiotic amount of trust.
(This beer will be ready Spring of 2017 and due to the limited amount will not likely see public release, sorry)