Routeinely Stuck Fermentations

[2wide]

+1 on adding most of the simple sugars near high krauzen during the ferment for better attenuation.

 

[leechdemon]

Alright, as suggested I've made a 1gal mini-batch of beer similar to the style of my latest stuck batch. This time I shook the bejesus out of it for a full 5 minutes. I hydrated 11g of fresh Nottingham yeast (what the yeast calculator suggested for my original batch) for 15m and pitched it.

I'll let you guys know how it goes. Thanks again for your help!

Alright, it's been a few weeks, here's where I'm at.

To review, SG was 1.068, it stuck after about a week at 1.042 and held steady for a week. Someone suggested an O2 problem, so I made 1gal of the same recipe and shook the fermenter like hell for 5m. After 1 day it peaked, and I added it to my main batch. I checked it after 2 weeks, and it dropped to 1.022. I checked it again yesterday (3 weeks after the mini-batch addition) and it's still at 1.022, so I think it's stopped again.

What I think has happened was that the mini-batch provided more than enough O2 for a single gallon of wort, and, as hoped, carried over to partially supply the original 5gal batch with more much-needed oxygen. The Gravity dropped, but not all the way. I'm thinking that 1gal simply can't hold enough oxygen to supply a 5gal batch, and that my fermentation went as far as it had the oxygen to go. So if 1gal got it a 0.020 drop, a second gallon would have enough O2 to drop it from 1.022 to wherever the FG will end up.

So, I'm thinking the last fix will be a second gallon addition, well aerated, to provide the remaining oxygen needed to get to FG. If that works, then I think the problem would be correctly diagnosed as a lack of oxygen. I'm definitely planning to give a vigorous shake the next time I do a full batch, and prevent this problem altogether.

Anybody got any opinions on the contrary? Am I tempting fate with too many additions and checks?

 

[jkreuze]

OK, now I'm going to really confuse the issue. Check out this series of interviews with brewing expert, Eric Watson, on Beer Tools:

http://www.beertools.com/html/articles.php?view=245

Here's Eric's surprising advice on aerating wort:

"If possible, don't! The reason is that it is not the wort that needs the oxygen, it is the yeast. By oxgenating the wort instead of the yeast starter, it will cause an over production of cells due to the excessive oxygen presence. This then leads to the production of unwanted esters and higher alcohols that will compromise beer flavor."

So it's actually the starter you want to aerate.

He continues, "When oxygenating starters, you cannot use pure O2... the reason is that the uptake occurs too fast and without a dissolved O2 meter ($$$), you cannot tell when to stop. The way to properly do this one is to aerate using a high pressure aquarium pump, sterile air filter and a stainless steel aeration stone, all of which are redily available. It is virtually impossible to over-aerate using air, so you will avoid oxygen toxicity problems that will occur if trying to do this with pure oxygen."

When using dried yeast, he recommends NO AERATION at all. The yeast was properly aerated before drying and has been properly prepared for the fermentation immediately. Just rehydrate the yeast (he recommends 90deg water) for 30 minutes and dump into the non-aerated wort.

That's some wild and crazy stuff, huh?!!!

My personal experience backs up the oxygen toxicity problem. I used to pitch the yeast then aerate with pure O2 for several minutes. The result was huge lag times, slow ferments, and high final gravity.

So if you're running your starter on a stirplate for two days, with a vortex, are you pulling in enough oxygen for more than adequate oxygenation of your starter? Hmm.

 

[2wide]

I'm getting a little confused in sorting out your past problems of high FG vs the stuck fermentation you have now. Stuck ferments are a special animal. I think you may reach a point where further meddling with this batch could do more harm than good. If it tastes decent--especially after aging and regardless of the FG--you might just bottle it up and plan for your next batch. Or set it back in secondary for a month in the meantime.

As for why you are having repeated low attenuations-- As said above, there can only be so many reasons. Healthy dry yeasts are usually go-getters. You might check into a product for re-hydrating dry yeast called 'Go Ferm'. Go Ferm is used only for re-hydrating dry yeast. This in conjunction with a yeast nutrient in the wort should mostly rule out problems at the start of fermentation. That's assuming re-hydrating procedures are correct and the yeast ain't fried in the sachet.

The advice to check your hydrometer is also a good idea. They can be as off as any other tool.

Hope this helps.