Monday, June 25, 2012

Freeze Condensing the Eisbock - Photos and Video

After a month of primary fermentation and a month of lagering, it was time to perform a critical process step in the brewing of our collaborative Eisbock – freeze condensing the beer. We have the Kulmback region of German to thank for originated this beer style, wherein a portion of water in the beer is frozen off and removed in order to intensity the beer’s maltiness, body, and alcohol. On a homebrew scale, this freezing process can be accomplished with two corny kegs, a beer line jumper, and a freezer, which is exactly what I did.

Given that this was the first time I had attempted to freeze condense a beer, I kept my camera close by to photo-document how I implemented the process.  While I was planning out what I would do, I did spend some time searching the web for examples of how other homebrews had implemented the freezing steps.  Sadly, I found several generalized descriptions about making eisbocks, but very few descriptive or image intensive sources to help an eisbock newbie.  So below I am sharing the step-by-step photo log of how I did it along with some commentary.  Whether it is correct or incorrect, I felt the need to leave behind a little more information than what I was able to find in the chance that someone, someday may find it useful.

Step 1: Obviously before a beer can be freeze consensed, a good base base beer is requiremed.  Our beer (comically named Frosty Fool) has been sitting in a keg (i.e. the "original" keg) at 38 degrees F for almost a month at this point. 


Step 2: A second keg (i.e. the "recieving" keg) has been cleaned, sanitized, and CO2 purged in order to recieve the beer after the freezing process. 


Step 3: In order to transfer the condensed beer from one keg to the next, a jumper line is needed.  You can purchase one from a homebrew store (such as this one), or one can just as easily be assembled from some beverage tubing, two beer line quick-connects, and a pair of hose clamps.


Step 4: Make sure to sanitize the jumper line prior to any transfers.  After sanitizing the recieving keg, I left about a half gallon of sanitizer in the keg and pressurized it.  With the jumper line was connected, depressing the inner pin on the unused quick-connect allowed the sanitizer to get pushed through the jumper line.  The nice part about this was that after all the sanitizer was run out, CO2 was blown through the line clearing it of any liquid.


Step 5: The freezing process.  The original keg was placed into my small, tempurature-regulated chest freezer (as seen in Step 1) and I dropped the tempurature down to 0 dgrees F.  Even though the beer was just above freezing tempuratures at the start, it took approximately ten hours in the chest freezer before it was ready to move onto the next step.    

During the freezing process, I kept shaking the keg to listen for ice crystals forming in the beer.  When the "slushing sound" gets more and more noticable, the freezing process is almost done.  However, defining when the process is complete is very subjective.  Given I had no experience with this, determining when the sound was "slushy" enough certainly tried my confidence.  In all honesty, the only reason I stopped the freezing at ten hours was due to the fact that it was 1 AM, I was tired, and I wanted to get to bed (and leaving the keg in the freezer for another 6 hours was not an option).  Luckily it turned out to be the right decision, as the amount of beer that was frozen was close to what I was targetting.

Below are two videos I snapped as I was hoping the audio would pick up what the slush sounded like when I called it done.  (Make sure your sound it turned on before playing.) 

video
Calibration Sound - this is the beer when it was just placed in the freezer (i.e. 100% liquid).

video
The slush sound at the end of the process (after ten hours in the freezer).

Step 6: After the freezing was deemed complete, the beer was transfered from the oringial keg to the recieving keg via the jumper line and the application of gas pressure to the original keg.  I was concerned that the freezing process might have frozen the original keg's dip tube or connector post, but the beer flowed smoothly as soon as the gas was turned on.


Step 7: Once all the liquid was run out of the original keg, I did let the gas continue to push through the line for an extra 10-20 second to make sure everything that I could got pushed through.  When the gas was turned off and the jumper line was disconnected, the recieving keg (and the eisbock inside) was finished.  The beer was moved back into fridge at 38 degrees F for another month of lagering before it will be ready for any type of consumption.

In order to determine how much was removed through the freeze condensing process, I opened the original keg and looked inside.  The beer slush would need to be measured so I could calculate the consensing ratio which would allow me to recompute the beers FG and ABV.


Step 8: The nice part of the corny kegs is that their stainless steel walls are great conductors of heat.  To quickly melt all the beer slush, the original keg was placed in a hot water bath with the water only touching the bottom 6 inches of the keg (where the slush was residing).  It only took about 15-20 minutes for the heat to penetrate the keg and completely melt the beer slush.

Keg in a warm water bath
Going....

Going...

Gone.

Step 9: Once everything in the keg was melted, I closed up the keg and applied gas to it,  This allowed for the beer to be carefully poured through a cobra tap into a measuring pitcher to be measured.  A total of three quarts were left behind, or 15% of the total volume.  Sources had suggested to target about 1 gallon of liquid to remove from a 5 gallon batch, so while I was a little under the target, I was quite pleased I got as close as I did just by listening to the slush in the keg.

One surprise, however, was the amount of color that was left behind in the melted slush.  If I was able to extract just the frozen water, the melt should have been clear or incredibly light colored.  But the color was much darker, indicating that other components of the beer got trapped in the ice crystals and were removed.


Step 10: With the freeze condensing completed, I had to do a side-by-side comparison of the beer.  Prior to placing the original keg into the freezer at Step 1, I poured 3-4 oz into a glass and covered it.  After the freezing and transfer, I poured another 3-4 oz from the condensed beer into seperate glass.  I had expected the condensed beer to be a little darker, but they were visually about the same in terms of color.  Upon tasting the two (both at room temperature), the condensed beer had a noticable higher intensity (both maltiness and sweet alcohol presence) as compared to the base beer - a result that was expected, but relieving at the same time. 

Pre-condensed on left; Post-condensed on right

*   *   *

New approches and processes always seem more involved/complicated when someone has never tried them before.  When the readers had selected the eisbock style for us to brew, I was pumped that I would get to explore the freeze conditioning process for the first time.  But the excitement was coupled with a little anxiety - nothing ever goes as planned and I didn't want to flub our collaborative beer if things went awry.  Despite the trepidations, the two unexpected elements were minor and easily items that could be planned for the next time around.  

Now it is back to the waiting game.  The condensed eisbock is back in cold storage for several more weeks to help mellow and meld the beer's components together.  Tom and I have a family function together in late July, so I would expect that will be the first time we'll be able to taste the finished product.

Given I am a bit of a feedback junky, please leave us a comment if you've brewed an eisbock and let us know how your freeze condensing process compares with how we did it.  

Slainte!

-JW


"There are two reasons for drinking: one is when you are thirsty, to cure it; the other, when you are not thirsty, to prevent it."
-Thomas Love Peacock 

9 comments:

  1. I've got a doppel lagering right now that I plan on turning into an eisbock. I've got it lagering in two 3 gallon kegs, plan on "eising" one of the small kegs. I, like you, have found very little information on the process. I've been torn on how I should do it, leave it in the keg like you've done, or using a bucket lined with a paint strainer bag and essentially pulling the ice out. Seems like the bucket method might oxidize the crap out of it though. I'm surprised at the color of your melted ice, I would've expected quite a bit of color loss, did you take a gravity reading on the melted ice? Did you taste it?

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  2. StoneHands,

    Thanks for the feedback - we appreciate it. After completing the process, I would certainly advise to do the freezing in a keg - it was simple and kept the beer protected from contamination/oxygen during the whole time. The bucket method should work, but for a beer that you want to keep for a long time, the risk of oxidizing or contamination is something that I would want to avoid if I could.

    I really wished I took a gravity reading of the melted beer slush. Because it was late at night, I did not think about it until the next day at which point the slush was had already been dumped. I may try to do a gravity reading on the finished beer and use the gravity change (compared to the FG measured when it game out of the fermentor) as another indicator of the concentration ratio. Thanks for the idea.

    All the best with your eisbock!

    -JW

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  3. Great little tutorial, thanks for that. I've been discussing the best way to do this with some buddies of mine. We were thinking fo anything from an icecream machine, to a bucket. You're right, oxidation is a big concern.
    We had thought of freezing the beer in a bucket, with the lid shut tight and wait for the beer to solidify on the top and outside of the volume of beer, then perhaps tap a hole in the top and transfer the center liquid to a keg. not sure how this is going to work but might be worth a try as well.

    Thanks again for publishing.

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  4. How full was your keg prior to freezing?

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  5. The full 5 gallon batch was in the keg that I put through the freezing process. You can see the condensation/freeze line on the side of the keg (just below the black rubber top) in the first photo at the top of the page. This gives a good indication of where the liquid level is inside.

    Thanks for the comment!

    -JW

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  6. Thanks for the write-up! I just brewed a tasty dobblebock and decided to take 1 gallon (of the 5) and take a stab at an eisbock. I've had the fermented beer at 40 degrees for 3 weeks and just put it in the freezer. I'm not sure how long to wait before skimming ice off of the top. If I leave it too long will I end up freezing the entire batch? I was thinking of marking the sidewal of the topped-off container about a 1/4 of the way down and skimming until I reached the mark. What would JW do?

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  7. If you leave the container in the freezer long enough, the entire thing will freeze in time. The trick is that you want to get it when the water is just starting to freeze (i.e. slush) but has not completely locked up (i.e. frozen block).

    The idea of skimming off the ice/slush as it forms is how I know a bunch of people do it. So it completely feasible. However, I was very worried about oxygen pick up into the beer, especially when there is repeatitive skimming of ice. So I opted to freeze the keg where I know there is a blanket of CO2 protecting beer the whole time.

    Just my opinion. Best of luck and let us know how it turned out!

    -JW

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  8. Awesome write-up! I just used your method for my own Eisbock and it worked perfectly. Thanks for putting this out there.

    I did the keg method and pushed it with CO2 just like you described, and it went really smoothly. Wrote it up here: http://cdbrewing.com/2013/03/29/eisbock-a-journey/

    Happy brewing!
    -Kevin

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  9. Kevin,

    Thanks so much for the feedback and I'm glad you were able to use our experience as a resource.

    Slainte!

    JW

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