Very stuck brew

[elkdictation]

Hello, this is my second time homebrewing cider. My yeasts seem to have given up, and I've tried all the advice I could find on this forum and elsewhere, so I come to tell you my cider's tale in the hope of getting a better understanding of what might be going on!

My friend has a number of old apple trees in his yard. Around December I ran the apples through a home tabletop juicer, then hand squeezed the pulp through a fine gauze. I did two batches from the same orchard, pressed a few weeks apart, 12 and 8 liters. A few years ago we made wild-yeast cider with different apples and proper equipment, and I loved the results, so decided to try wild yeast fermentation here as well.

I racked both ciders twice. By early February, after around six weeks of fermentation, the 12l one stopped at SG 1.0200, the 8l at 1.0078. I let them sit some more, but after a month in my 59 degree F cellar, neither had moved a wink.

I thought the cellar might be a bit cold, but bringing the cider upstairs and indoors into 69F temperature made no difference.

I have learned on this forum that old unfertilized apples -- the type in my friend's yard -- can be lacking in YAN and nutrients. I added a very small amount of Servomyces nutrients. I read around and found guides specifying ppm, and calculated it out roughly to dipping the tail of a spoon into the nutrients and adding that to the 12l batch. It made no difference.

I tested the PH - again, don't remember the exact value, but nothing unexpected from what I could find online.

Finally I brought a jar of the cider upstairs and added coobra cider yeast to it. It fermented for a bit, then stopped at 1.0193.

At this point I'm rather out of ideas. Is it possible I simply didn't add enough yeast to the sample? Maybe the countertop juicer pulverized too many seeds, and added enough cyanide to the mix to kill yeast? My carboys are not very full, maybe too much surface area and oxygen spoiled the process?

I should add that both taste absolutely delicious. I was really hoping for sparkling cider though and not apple wine!

 

[Chalkyt]

I am not familiar with servomyces yeast as a nutrient. Dr Google suggests that it has lots of valuable trace elements but says nothing about nitrogen (YAN).

From your description, my first guess is that the yeasts have simply run out of nitrogen and stalled (it has happened to me when using late ripened apples from my old unfertilised trees). I wouldn't expect the other issues you mentioned to have much to do with the problem, although they are not ideal.

You can reasonably expect "normal" apples to have 50 - 100 ppm of YAN so fermentation from 1.050 to 1.000 shouldn't be a problem. But sometimes YAN can be less than 50ppm resulting in stalling (my problem batch stalled at 1.012).

The "rule" regarding YAN is that for a stalled fermentation, you need to add 10ppm of YAN for each 10 gravity points you need to ferment. So as DAP is 20% YAN, add 50ppm (0.05g per litre) for each 10 gravity points yet to ferment.

If the problem is lack of YAN, about 1/4 teaspoon of DAP (12x0.05x20/10=1.25g) should finish the 12L batch quite quickly. Apply the same logic to the 8L batch (i.e. say about 1/10 teaspoon or 0.5g).

Good luck!

 

[elkdictation]

Your guidance is as invaluable as ever, thanks! I ordered some DAP and, on a hunch, also added a much nicer hydrometer to the order, which revealed that the one I've been using lies.

The new meter reads water as 1.000 and my cider (correctly, I presume) as 1.012. The old meter meanwhile seems to read water at 1.000 and the cider at 1.0200!

Sure enough, I microdosed some DAP into my small upstairs sample, and within half an hour it started right up again.