December 17, 2012

Cider Keeve

I have been working with Leidel's Orchard up in La Cresent, MN.  They are looking into making hard cider, and after much discussion/research/brainstorming with the owners about the type of product they want to make, our pilot batches include a "Saison barrel", a "Natural barrel", and a "Keeve carboy".  I'll wait for another day to talk about the barrels, but I wanted to post a bit on the keeve batch.

Keeving is a old-world cider technique that has largely been forgotten, but is still done by some traditional cider makers in the UK and France. Simply put keeving releases natural pectin into the apple juice which then coagulates, removing much of the nutrients from the juice. As the yeast ferments the keeved juice, it uses the remaining nutrients, but runs out before it can ferment all of the sugar.  Traditionally, this has been done to create a naturally sweet cider.  For more information on the process, read this.

When I learned about this process and how it works, I thought about how lambic wort is brewed to have a lot of complex sugars that Saccharomyces can't eat, which leaves a portion of the sugars for the Brettanomyces.  I began to wonder if Brett would survive in a nutrient poor environment after the Saccharo died out.  So the purpose of this experiment is to see what will happen if I pitch lambic yeast into keeved cider.

However, this turned out to be a very difficult and laborious process.  I started with nearly 4 bushels (160lbs) of apples.  They had to be sent through a mill and the pulp left to sit for 24 hours (to release the pectin).  The next day we pressed the pulp, but our efficiency was about half that of a commercial cider press (and 10 times the work).  Leidel's Orchard actually spoke with a couple commercial presses keeving, but they were unable to do this process without a major rework of their set up.  I was hoping to get 8+ gallons, so I borrowed a friend's 12 gallon glass carboy to use as a keeving tank.  I only ended up with 6 gallons.

Then the keeving process starts.  The first step is to allow the pectin to coagulate in the cider.  Some modern additives help this process, but it is still a bit of an art.  The carboy was stored in my refrigerator for 10 days where it is cold enough to stall fermentation until the coagulated pectin gel has formed.

Coagulated pectin during a cider keeve.
Most of the gel that formed fell to the bottom and is sitting on top of the sediment
The next step is to allow fermentation to start and the CO2 bubbles will lift the coagulated pectin to the surface making it possible to siphon out the juice in the middle.  I left it at room temperature for 5 days, which is much longer than I was told to expect, and only had a minimal amount of fermentation start.
Cider keeve separation
Separation of cider and pectin gel.
Pectin gel pushed to the top by CO2 bubbles.
Pectin gel pushed to the top by CO2 bubbles.
Only about half of the pectin gel was pushed to the top, while the rest stayed on the bottom of the jar.  I would have liked waiting until all of the pectin was pushed up, but I feared fermentation would accelerate too fast and I would be left with a cloudy cider.  Also, as the pectin gel at the top was exposed to the air, some mold was starting to grow.  I decided it was best to siphon at this point rather than risk ruining the whole batch.  As I siphoned, I also strained the keeved juice to capture any particles that might have been stirred up.

5 gallons of keeved cider with lambic blend yeast
5 gallons of keeved cider with lambic blend yeast added.
In the end I was left with 5 gallons of clear, keeved, cider.  To that I added Wyeast Lambic Blend.  It will likely take 9-12 months before I know if the experiment worked, and if its anything like lambic, may take 2 years to really develop.  Apple cider is all simple sugars, and normally the Saccharo would out compete everything else.  My hope is that I've stripped out enough nutrients in this keeve to slow the Saccharo and allow the Brett/Pedio/Lacto to do their work in tandem.
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