Big beers getting stuck

[Phlegmcaster]

I've had two big beers get stuck at about 60% attenuation...extract brews, OG 1.129 (1.7 gallon batch) pitched 11.5 g sachet S-04 (no rehydration), went like gangbusters until 1.050, then nothing...1.101 OG (1.7 gallon batch), used WLP007 w/1 L starter. Fermented down to 1.034 and stuck. Nothing for a week, so I racked it to the secondary. Both were fermented in ambients of 66-68 F. Any ideas?

 

[sbaclimber]

I am not particularly experienced, but my first guess would definitely be underpitching!
I used WLP007 exclusively for almost 3 years (30+ brews) and never had one get stuck. My OG was generally 1.060-1.080ish (depending on brew) and the one thing I found helped alot for good attenuation was a big starter, at least 1.5-2l. What didn't make a huge difference in most of my brews but was still benefitial (when I had time to do it) was a good dose of aereation. With an OG of 1.101, I could well imagine that the yeast is simply running out of oxygen...
I am now using US-05, and even with an OG of only ~1.055, I still put in 2x 11.5g packs. At 1.129, I would think you should definitely be putting in more than just one....and aereating.

 

[Hogarthe]

since your batches are only 1.7 gallons, you should have enough yeast, but check a pitch calculator to be sure. the big question I have is how did you aerate? for beers that big, you probably want to get an oxygen injection system to pump pure oxygen into it.
the other thing is extract. which brand did you use? some brands are more fermentable than others, and a lot of people have extract beers get stuck. sometimes it seems even when everything is right, they just like to get stuck. but if you use the most fermentable extract you can, you will minimize this.

 

[sbaclimber]

since your batches are only 1.7 gallons, you should have enough yeast

D'oh! I read right over that, and was assuming 5 gals...
According to the calculator, for a 0.75+ Pro Brewer pitch rate, 2 packs would still be minimum though.

 

[Ozarks Mountain Brewery]

not enough oxygen or a bad batch of yeast can do that, don't pay attention to the people saying to just shack your carboy, you need a good 3 inches of foam on top on any beer for a good fermentation

 

[Phlegmcaster]

Thanks for the input, all. Here are some more of the details:

The first batch was made using 6.6 lbs Munton's Extra Light Liquid extract from a can. The second was with Briess golden light, fresh from the HBS. It was less than a month old.

For oxygenation, I pour into the carboy, and then agitate by rocking for 8-15 minutes. I don't know that I had 3 inches of foam on the wort after aeration, but it was a solid 2.

I checked the pitch calculator (from this site, actually) for both of the beers. The first called for 11g S-04, and I pitched the whole 11.5 g sachet (I did lose an extra quart on this boil and that threw my OG up, and I also only used .50 on that one. Live and learn). The second called for a 1L starter with the WLP007, and I plugged in the correct date for viabilty calculations.

Both of these went nuts initially, the S-04 fermentation blew the airlock off the carboy.

Sounds like I need to aerate better, and overshoot my pitch rate by a bit to ensure better fermentation. Anyone ever split a pitch, put in 1/2 at onset and 1/2 at 12-18 into fermentation?

Again, thanks for the help!

 

[Ozarks Mountain Brewery]

I was in a hurry and didn't get to think about this before but there are numerous reasons this could happen, a couple that come to mind are a solid krausen sealing in the carbonation from getting out which can result in carbonation build up causing the yeast to slowly die sooner since the carbonation will push the oxygen up

another is too much blow off, essentially blowing out most of the yeast already replicated and not having enough to eat all the sugar

try using some yeast nutrient at the end of your boil

 

[The Brew Mentor]

I'll chime in...
When you plan a "Big Beer", there are a few things you need to make sure of.

1) Plenty of healthy yeast.
According to Fermentis' website an 11.5 gram pack of yeast contains > 69 billion cells. It doesn't say how much more but I use that as a base number. The site also says to properly rehydrate before pitching.
http://www.fermentis.com/wp-content/upl ... A_US05.pdf

2) Good aeration
Shaking is fine initially but should be repeated after 12 hours to insure the daughter cells have enough oxygen for strong cell structure. Pure oxygen is better but not necessary.

3) Head space
A minimum of 25% head space is required on a big beer and sometimes more is needed!

4) Temperature control.
All of your fermentation's should be temperature controlled. This is especially important on larger beers. Remember the ambient temperature doesn't reflect the internal wort temperature. A Swamp Cooler is an easy, cost effective method of controlling your fermentation's.

I've never heard of Krausen blocking a fermentation. Many commercial brewers actually seal up their fermentation tanks towards the end of fermentation to naturally retain and carbonate their beer before moving it to Brite Tanks. It's free and it works!

I hope this helps in your future brews.
Brian

 

[Dodes]

1) Plenty of healthy yeast.
According to Fermentis' website an 11.5 gram pack of yeast contains > 69 billion cells. It doesn't say how much more but I use that as a base number. The site also says to properly rehydrate before pitching.
http://www.fermentis.com/wp-content/upl ... A_US05.pdf

From what I've read that count is the *guaranteed* one. But on the average there are 150 billions cells in the one 11g pack (http://www.homebrewtalk.com/f163/dry-ye ... ng-435798/).

4) Temperature control.
All of your fermentation's should be temperature controlled. This is especially important on larger beers. Remember the ambient temperature doesn't reflect the internal wort temperature. A Swamp Cooler is an easy, cost effective method of controlling your fermentation's.

I prefer the fermentation chamber/temperature controller attached to fridge. Maybe there is more work to setup but then everything is automatic (I've also read someone implemented fully-automatic temperature controller using Rapsberry Pi/Arduino which could be programmed for full fermentation cycle (i.e. diacetyl rest after some time, etc.))

 

[Nosybear]

When doing big beers, I'll often use a "helper" yeast. I make a 1l starter of WLP 090 in the evening, let it sit on the stir plate overnight and pitch the next morning while it's still healthy and living large. It'll then clean up any remaining sugars in the beer and contribute very little flavor. It works well for me when I want to dry out a beer.

 

[Phlegmcaster]

Thanks for the help, everyone. I'll let you know how it turns out. I just had s 1.073 OG IPA go to completion with WLP001, no issues. Same 1 L starter, agitation, etc. Not quite as big, but big enough. No barleywines in the near future though.