Eisbock Tips from the Pros
Getting your hands on an eisbock in the U.S. can be difficult because of federal and state laws around distillation that limit the amount of ice commercial brewers may remove to concentrate the beer (which is considerably less than is traditionally subtracted for the style). To avoid the need for a distilling license, most American breweries overlook the style. However, we have tracked down two pros who could not resist the temptation of bringing the potent German lager to America.
Jason Senior has worked for Mammoth Brewing Co. in Mammoth Lakes, California, since 2000 and has been the Head Brewer there since 2006. Jason was a homebrewer before landing a job at the brewery, where Jason’s recipes won multiple awards in last year’s Brewers Association World Beer Cup.
Our Fire and Eisbock, which was a seasonal offering available for the first time this past winter, was the first beer of this unique style I set out to make at Mammoth Brewing. We previously iced a pale ale and before that we made an eisbock out of a doppelbock by accident when some kegs froze in the winter. After freezing, we tasted the beer that had not turned to ice in those kegs and it tasted great! That mistake, much like how eisbock originated in Germany, sparked the idea for Fire and Eisbock.
This past winter we (intentionally) brewed 22 barrels of Fire and Eisbock. Our Eisbock has a very similar grain bill and hop character as our doppelbock. The big difference, of course, is freezing out a portion of the water, which concentrates the alcohol and creates a smoother finish.
For our eisbock, we used Weyermann CaraMunich®, Gambrinus Dark Munich, and Crisp Crystal 120 for the specialty malts, and Gambrinus ESB as our base malt. The hops we used were Sterling, just enough to balance the sweetness from all of the specialty malt. I also like to try and get a little bit of floral aroma into the beer. A piece of advice for anyone brewing an eisbock for the first time would be to make sure to get a complete fermentation. The icing will concentrate the malt flavors and sweetness of the beer so any unfermentable sugars will be more evident. Plan your bittering hops with that in mind as well.
I think an eisbock could be made at home pretty easily by sticking the beer in the freezer after fermentation and then watching for ice to form. At that point the ice could be skimmed off the top of the beer and racked from the bottom. For us, it’s a little more difficult; we have to rely on our glycol jackets to get the beer cold enough to start freezing. It is hard to coax our glycol unit down that cold with everything else going on in the brewery. That is why Fire and Eisbock is a winter seasonal. We use an outside fermenter and hope for really cold nights to help out the glycol. Our outside fermenters also have top manways so we can open them up and look for ice formation.
Fire and Eisbock is a lager, so we ferment it at 50 °F (10 °C) with a Mexican lager strain. After primary fermentation and diacetyl rest, we drop the temperature to 32 °F (0 °C) for a week and drop as much yeast as possible out. Then we drop the temperature down to 25 °F (-4 °C) and wait for it to start freezing. That’s what takes a while. Since we used an outside tank and turned off the glycol jackets at night, the beer temperature bounced between 25 °F (-4°C) at night to 29 °F (-2 °C) during the day for two weeks. After we saw ice formation and liked the flavor, we transferred the beer off the bottom and left the ice behind. Other than that, the brewing process is not any more difficult than brewing a doppelbock.
Eisbocks are a really fun style to make and concentrating it really adds something to the beer. It really does smooth out the beer.
Matthew Allyn, Founder and Master Brewer of Voodoo Brewery in Meadville, Pennsylvania, has been brewing professionally for 20 years. After studying brewing techniques in Germany, Matt returned to the states where he has started a handful of breweries across the country. Matt has brewed a number of eisbocks in his career. To the excitement of Pennsylvanians, Voodoo brewed Trapped Under Eisbock for the first time this past winter.
Eisbock is pretty much a freeze-distilled product. We do ours from an American dry doppelbock design along the lines of Troegenator. We freeze the beer and test its depth from the top where we have no direct cooling jackets. By the time the ice measures about one inch thick on the bottom of the tank it measures two to three inches thick on the walls. At that point we rack the beer into another tank to carbonate and package it. Removing some of the water concentrates the beer, thus concentrating flavor. This gives you a non-typical flavor that cannot be replicated from traditional brewing methods.
Brewing an eisbock is more difficult on a large-scale system than for a homebrewer, largely because it is difficult to get the large tanks cold enough to freeze-concentrate the beer. We run our chiller at 20 °F (-7 °C) for a month. We run glycol to the tank to freeze the outer layer of the tank faster than normal. This way the cold temperature does not absorb into the beer as much. The water on the outside freezes first, similar to how a lake freezes. Over time, the ice will slowly thicken until we feel we have frozen enough out of the beer.
After racking the beer, I take a measurement of the water that is left in the tank after it melts to get a clear idea of the beer’s alcohol content. If too much ice has been removed we may add de-aerated water to achieve our desired alcohol level and taste.
Trapped Under Eisbock sticks with a very standard German recipe using 50/50 German Pilsner and dark German Munich malt. To be different, we add fresh tart cherries for about a month after freezing. Any lager yeast strain will work fine. Like traditional eisbocks, ours has very little hop character. We go with a standard German strain, such as Hallertau, to add bitterness to the beer. The beer ends up at about 18 IBUs.
