CIDER PET NAT?

[Tim Bowman]

I have a couple hundred litres of some green apples i pressed and is currently fermenting (spontaneously) its reaching towards sg=1.02 (from 1.06) -  i am wondering if anyone has tried to do a pet nat style while there is still some bubbles left and bottled directly? if so, what is the safest bet to bottling this and ensuring it doesn't keep fermenting and blow up the bottle? 

thanks

[Claude Jolicoeur]

If I understand correctly, you are trying to make what is called a "Méthode Ancestrale" cider. This is routinely done in France and myself I make most of my ciders that way. The procedure is described in my book. In general this works best for ciders that have been keeved, but it is also possible to succeed with a cider that has beed racked a few times to depleate the nutrients and decrease the yeast population.

You may try the following procedure:

Rack your cider now and check the SG in 2-3 weeks. Compute the FSU.

If the FSU is higher than 10, rack again.

Ideally, you would want a perfectly stabilised cider at a SG of about 1.015. You may then wait until it clarifies naturally or you may fine it to accelerate the clarification.

Once stabilised and clarified, you may rack, bottle and add at bottling a micro dosage of DAP (10 to 12 ppm) which will just revive the yeast for the in-bottle fermentation, and the yeast will die after that from starving.

Good luck...

Claude

[Eric Tyira]

Hi Claude,

I'm reading your book now and just getting into the keeving section, but I have a question.

Why does racking in-and-of-itself slow down the fermentation?  I would think active yeasts are distributed throughout the must.  Or it is in the lees where most of the activity is happening in which case racking would remove the juice from the settled nutrients, bulk of yeast etc.?

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[Tim Bowman]

merci beaucoup  Claude

On Tue, Nov 13, 2018 at 11:16 AM Claude Jolicoeur <cjol...@gmail.com> wrote:

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thank you,

Tim Bowman

(905)-906-7053

[Claude Jolicoeur]

Le mardi 13 novembre 2018 11:21:38 UTC-5, Eric Tyira a écrit :

Why does racking in-and-of-itself slow down the fermentation?  I would think active yeasts are distributed throughout the must.  Or it is in the lees where most of the activity is happening in which case racking would remove the juice from the settled nutrients, bulk of yeast etc.?

There are a couple of different phenomenoms happening there.

First, part of the live yeast cells are in suspension in the cider while another part is in the bottom in the lees. So for this, the racking will eliminate the part that is at the bottom and leave those that are in suspension. Since the speed of fermentation may be assumed to be proportional to the amount of live yeast cells, we see the racking will cause a reduction of the speed of fermentation that is related to the ratio of live yeast cells eliminated by the racking.

Now, it is not easy to know what is the fraction of those that are in suspension, but you can be quite sure that the clearer the cider, the higher the proportion on the bottom and the more efficient the racking.

Many producers in France use a microscope to evaluate the number of yeast cells in suspension and this way they can better control the racking. Sometimes also they would filter a fraction of the cider during racking to further reduce the yeast population.

A second effect comes from the elimination of dead yeast cells in the lees. If left, these dead cells will slowly degrade and release the nitrogen they contain back to the cider, a process called autolysis. This released nitrogen will then be used by the live yeast population for feeding and maintain the population. By removing this supply of nutrients, you prevent them from reproducing and condemn part of the population to die from starving. Hence this causes a deceleration of the fermentation speed by a gradual reduction of the live yeast population.

Claude