Priming with Kreusen

Success! My Munich Helles has carbonated itself in the keg! So here’s the rundown. There are a couple of different ways to do this, and I actually ended up mixing a couple of them. Both of them require you to have a vessel capable of holding pressure. Do not attempt this in a glass carboy or bucket. It really needs to be done in a keg.

• Method #1: Save some extra unpitched (before you add the yeast) wort from the brew day. You’ll need 1-2 quarts, depending on the carbonation level you want. I used a couple of sanitized mason jars and froze them to prevent infection. When your beer reaches terminal gravity, rack to a keg and return to the fermentation fridge, cellar, etc. Combine your saved wort and a little left over yeast (similar to making a starter). Let it come to high kreusen, about 1-2 days at fermentation temperatures. At or just before high kreusen, pitch it into the keg. In 1-2 weeks you should have carbonation.
• Method #2: This one is a little simpler, but requires you to check the gravity of the beer somewhat regularly towards the end of the primary fermentation. As the beer nears terminal gravity, about 4-8 points short, rack to keg early. There will still be enough yeast in suspension to ferment the remaining sugars, and of course you will capture the remaining CO2 to carbonate the beer. While this isnt’ technically kerusening, it is also a traditional method for achieving natural carbonation.

In both cases, you’ll probably want to be able to monitor the pressure building up in the keg and vent any excess CO2. The easiest way to do this is with a Spunding Valve. You can build one yourself, but I ordered this one from MoreBeer. It’s a fairly simple device with a keg gas post connector on one end, a pressure gauge in the middle and na adjustable pressure release valve on the other end. Use a carbonation chart (like this one at northernbrewer.com) to figure out how many psi you need at fermentation temperature to achieve the desired volume of CO2 in the finished beer.

After my last failed attempt at natural carbonation in the keg, I went a little overboard and used both methods, racking slightly early and adding some fresh kreusen wort. I’m not sure that was the best idea, as after 2 1/2 weeks I’m still about 3 points short of the expected final gravity (1.016 vs 1.013), but it’s not the end of the world. Hopefully it will finish out this week, or over the next 6 months while it’s lagering away. For the Oktoberfest, I’m going to let it ferment out and then add my kreusen beer as per method #1.

Finally, While doing some research on this topic I found several links of interest, so here they are in no particular order.

• The Kaiser has a pretty good wiki style site with lots of info on Kresuening, and Lager brewing in general: braukaiser.com
• The Beer Barons have a pdf chart to help you figure out how much unfermented wort to use: BeerBarons pdf
• Gene Nelson wrote a nice article with more detailed steps and calculations: Yeastmeister article

Tagged as: brewing, experiment, ferment, krausening, kreusening, priming, yeast