Fermentation During Lagering

[mattbrewer]

Giday all.

I posted a similar topic a while ago but didn't quite get the answer I wanted, (thanks to those who replied). I can't get any definate answers from any source.

I am trying the lagering method where I keep my lager yeast actively fermenting while I drop the temperature from diacetyl rest/rack to my final lagering temperature. So I leave about 6 gravity points and drop the temp 2deg per day from 16deg. But I need to know how much attenuation to expect down at the lagering temps.

Specifically I am asking for peoples' experience and if anyone has taken SG readings throughout the lagering period.

Matt

 

[RagingBull]

A while back i used 2xSaflager Packs got a 22L of wort @ 1052 down to 1008. This was done at 13deg C with a diacetyl rest @18degC for a couple of days, dropped it then as you discussed at 2degC per day back to 12 then i crash chilled/racked/lagered Approx 84% apparent attenuation in the end. Hope that helps.
another tidbit, i started the diacetyl rest at about 1016, cheers. (Crash Chilled to lager 10 days from pitching.)

 

[mattbrewer]

Thanks. I am finishing my diacetyl rest at 1016 and then hoping to hit lagering temp at about 1012 with the remaining 2-3 gravity points being knocked off at the cold temps.

If it helps I am using a Wyeast Urquell yeast with a starting gravity of 1047.

Matt

 

[RagingBull]

Sounds like you're on the right track and using the right methods. There's so much information on here regarding lagering among other things so if you've done enough reading the weeks of lagering should be worth the wait.

 

[Kai]

I am trying the lagering method where I keep my lager yeast actively fermenting while I drop the temperature from diacetyl rest/rack to my final lagering temperature. So I leave about 6 gravity points and drop the temp 2deg per day from 16deg. But I need to know how much attenuation to expect down at the lagering temps.

What is the motivation behind trying to d-rest and decrease to lagering temp before you've reached final attenuation?

 

[mattbrewer]

I was inspired after reading a webpage on traditional German lager fermentation. They seem to ease the yeast into lagering quite early into the attenuation. I'm sure there is a brewer with experience in German techniques out there who could confirm or deny this, or point me in the direction of some good information. I thought I would try a version of their technique. I raised to a 60 hour d-rest after 60% attenuation.

It makes sense to me. The yeast is a living organism and keeping it active as long as possible will benefit the beer if not apart some different flavours.

I was hoping someone out there had tried different lagering methods and had an opinion.

Matt

 

[matti]

I am still befuffled over the question a bit.

I generally perform the diacetyl rest at 2/3 of the way the fermentation.
This would be around 1.018-1.024 depending on OG.
I rest at 16-18 for 48 hour and then I drop the temperature a few degrees every day until I reached Nadir.
I generally get it down to 2 degrees after 3-4 days.

The yeast still work for during the lagering period but I don't think it is necessary to check the SG as the more you fiddle with a lager the more likely you are to spoil it.

Your are right on track.

If you are intrigued by Lager methods and technical aspect of brewing lager any any other beer Gregory J Noonan and "New brewing lager beer"

If you pitch enough yeast at beginning you can reduce or forget the diacetyl rest all together

MAtti

 

[mattbrewer]

Yeh thanks for that. Sounds like everything is good.

Seems that people I ask ensure that the attenuation is completed with the d-rest then immediately drop the temp to lagering. I suppose the reason for this is to guarantee that fermentation is over. It just didn't seem right to me.

I suppose I'm still interested at what rate sugars are utilised at very low temperatures. As you say I don't want to disturb the beer and I haven't got the time to sit around and listen for bubbles.

Matt

 

[t2000kw]

It appears that the diacetyl rest is done around the point where fermentation is about 3/4 finished, then you rack and lager. You can determine the point by taking the OG minus the FG and figuring where your SG is about 3/4 of the way down towards FG. This assumes that you have an expected OG and FG for your recipe, or know the attenuation of your yeast and calculate it yourself. It's not rocket science, and if you're off a bit on the high side, you'll just have to wait longer for fermentation to completely finish since it will progress slower at lagering temperatures.

These pages might help:

http://www.howtobrew.com/section1/chapter10-4.html
http://www.howtobrew.com/section1/chapter10-5.html

and while this isn't pertinent to your question, this part about what to do if your lager accidentally freezes is humorous. The poem about what happened to the author has more than a faint similarity to The Night Before Christmas poem.

http://www.howtobrew.com/section1/chapter10-6.html