Stuck fermentation?

[thepgr...@gmail.com]

I have 8 5-gallon batches of cider from an early October pressing. Most batches in buckets, and two batches in glass carboys. I thought they were all moving along by looking at the bubbles in the airlocks. I tested SG today, and found some were fermented to complete dryness, and others were gettting below 1.010.

EXCEPT for the batch of 50/50 Bramley Seedling and Bosc pear. It was actually the first to show signs of fermentation (and erroneously assumed I had a possible keev) and I posted photos here.  It stopped bubbling a while back, but I just assumed it had run its course. But when I tested for SG there is obviously something wrong. From Oct 10 to 27 it has only dropped from 1.050 to 1.044. 

Could my yeast have been bad? But they initially seemed to be fine. 

Is there not enough nutrients? I'm on my fifth year of cider making doing about 30-50 gallons a year and have never added yeast nutrients to any of my batches - so wondering why this might be the case. Also both these varieties were blended into other batches that fermented to dryness. 

I want to rescue this juice. Should I add a new yeast? 

[terryc...@gmail.com]

I have come across this problem occasionally, but closer to finishing (around SG1.010 +/- a bit). After adding yeast+dap it has started up again, however afer searching through Claude's and Andrew's books it looked as though the problem might be depleted nutrients. This might not be your problem as your SG seems too high for the nutrients to be too depleted already, nevertheless I have thrown it up for you to consider, especially as you were thinking of keeving.

This year I found that adding a small amount of nutrient (no extra yeast) starts fermentation going again. You might like to try that with a small sample.

My rationale is that it only seemed to happen to me with S04 yeast which is a nutrient dependent ale yeast, and with "late" batches using well ripened fruit from unfertilised trees which can be low in YAN.

[Andrew Lea]

It could perhaps be nutrient depletion depending on the source of your fruit (eg big old trees). In which case a little thiamine / DAP may help. But there is nothing inherently bad about a slow fermentation. A 6 point SG loss in 2 weeks is not unusual where I come from. 

But remember that pears often contain unfermentable sorbitol to a significant degree. I don’t know anything about Bosc, but it’s not unknown to get residual gravities as high as 1.020 with some pears in some seasons.  So your final gravity for this blend might be say 1.010. In which case the speed of attaining it will obviously be different to that of your pure apple batches.

Andrew

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[thepgr...@gmail.com]

Thanks, Andrew and Terry. I added some yeast nutrient three days ago and now there is regular action in the airlock again.