thecebruery
Active Member
So I have two stuck fermentations right now - the power to my yeast freezer failed while I was out of town, and my stored slurry went through some pretty rough temperature fluctuations that obviously lowered their vitality more than I anticipated. I have a 1.075 dubbel that's conked out around 1.030 and a 1.055 pale ale that's conked out around 1.020. I've brewed both recipes before numerous times and expect the former to finish at 1.015 and the latter at 1.014.
I've put in orders for more dried yeast, and am in the process of cold crashing and fining both beers w 1g/gallon of gelatin at 4.4C for 48 hours to remove all the dead yeast and stress/shock proteins in solution.
Obviously, when you pitch X billion cells of yeast in to a well aerated beer, you end up with ~4x billion cells of yeast after the growth phase has ended, and those 4x billion cells chomp their way through everything and go to sleep.
With a stuck fermentation (even one that's been cleaned of stress proteins and lysed/lysing yeast cells), things are a little different:
a) There's less sugar;
b) There's more alcohol;
c) There's practically no oxygen.
So there's almost no growth potential and it's a more stressful environment right out the gate with regard to alcohol, but a less stressful environment with less work to be done w/ re: to sugar content.
Also, I will be repitching with rehydrated dried yeast - there's enough information out there warning against making a starter with dried yeast (even when you want to pitch at high krausen, as with a stuck fermentation) that I think it'd be best just to pitch rehydrated dried yeast.
So the question I have for everyone here is: what is the ideal pitch rate for a stuck fermentation? Is it four times as much as you'd pitch for the unfermented wort, given the fact that there's no growth potential? Is it four times as much as you'd pitch for an unfermented wort with the same gravity as your stuck beer? Is it somewhere in between those two numbers, due to the fact that the sugars remaining tend to be the hardest to ferment and the environment is already moderately alcoholic?
To use specific numbers, I initially pitched 350g of 15 month-old Fermentis Abbaye in to 100 gallons of my 1.075 dubbel. Mr. Malty calls for 422g with those stats, but I wanted to underpitch by about 15% to encourage ester production (lesson learned!). That's 5145bn cells, which will presumably become around 20000bn cells in a normal, well oxygenated, happily fermenting batch. The beer is now at 1.030, so it's about 5% abv - a "wort" that Mr. Malty recommends pitching 123g in.
If no one knows the answer to this, should I err on the side of caution and just pitch an entire rehydrated 500g brick? That would be a little more than the "low end" estimate (4 times 123g) based on a reasonable growth rate and the actual sugar content but not taking in to account the stress caused by the lack of easily fermentable sugars and alcohol already present.
I've put in orders for more dried yeast, and am in the process of cold crashing and fining both beers w 1g/gallon of gelatin at 4.4C for 48 hours to remove all the dead yeast and stress/shock proteins in solution.
Obviously, when you pitch X billion cells of yeast in to a well aerated beer, you end up with ~4x billion cells of yeast after the growth phase has ended, and those 4x billion cells chomp their way through everything and go to sleep.
With a stuck fermentation (even one that's been cleaned of stress proteins and lysed/lysing yeast cells), things are a little different:
a) There's less sugar;
b) There's more alcohol;
c) There's practically no oxygen.
So there's almost no growth potential and it's a more stressful environment right out the gate with regard to alcohol, but a less stressful environment with less work to be done w/ re: to sugar content.
Also, I will be repitching with rehydrated dried yeast - there's enough information out there warning against making a starter with dried yeast (even when you want to pitch at high krausen, as with a stuck fermentation) that I think it'd be best just to pitch rehydrated dried yeast.
So the question I have for everyone here is: what is the ideal pitch rate for a stuck fermentation? Is it four times as much as you'd pitch for the unfermented wort, given the fact that there's no growth potential? Is it four times as much as you'd pitch for an unfermented wort with the same gravity as your stuck beer? Is it somewhere in between those two numbers, due to the fact that the sugars remaining tend to be the hardest to ferment and the environment is already moderately alcoholic?
To use specific numbers, I initially pitched 350g of 15 month-old Fermentis Abbaye in to 100 gallons of my 1.075 dubbel. Mr. Malty calls for 422g with those stats, but I wanted to underpitch by about 15% to encourage ester production (lesson learned!). That's 5145bn cells, which will presumably become around 20000bn cells in a normal, well oxygenated, happily fermenting batch. The beer is now at 1.030, so it's about 5% abv - a "wort" that Mr. Malty recommends pitching 123g in.
If no one knows the answer to this, should I err on the side of caution and just pitch an entire rehydrated 500g brick? That would be a little more than the "low end" estimate (4 times 123g) based on a reasonable growth rate and the actual sugar content but not taking in to account the stress caused by the lack of easily fermentable sugars and alcohol already present.
