Is diacetyl rest necessary for lagers?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk:

Andreas

Active Member
Joined
Jan 17, 2009
Messages
34
Reaction score
0
Location
Burlington
Hi,

On a scale of 1 to 10, how necessary is the diacetyl rest to the process of making good lagers (incl. pilsners)?

Another way of phrasing the question: if one doesn't bring the fermentation up to the higher temperature, will the beer necessarily exhibit diacetyl traits (like buttery mouthfeel)?

If I ferment a lager for a sufficiently long period of time at 48 degrees, will the yeast take care of the diacetyl, or is it necessary for this to happen at a higher temperature (and if so, which temperature range is recommended)?

I'm brewing a number of lagers, in various stages now, all using saflager yeast (I believe it was called S-23).
1. Rye lager, has been in secondary for 3 weeks after 2 week primary at 48*.
2. Bohemian-style pilsner, primaried for 3 weeks at 48*, now in secondary.
3. Vienna lager, in primary since Sunday, pitched on top of the pilsner's yeast-cake, wickedly powerful fermentation even at 48*!

Thanks in advance for your perspectives,
Andy
 

AstroBrew

Active Member
Joined
Nov 29, 2008
Messages
41
Reaction score
0
Location
Austin, TX
My understanding is that it can take months for the yeast to clean up the diacetyl at 48*F. However, diacetyl is a by-product of yeast growth during the first few days of primary fermentation. So, the less the yeast need to grow, the less diacetyl will be produced. However, even with a really big starter, in a clean lager, such as a pilsner, the diacetyl may still be noticeable.

What I am currently experimenting with in a pilsner is this. I re-pitched the entire yeast cake (minus trub) from a bock lager that I had just finished into the pilsner and did not aerate (because oxygen is only necessary for yeast growth). I am trying to avoid the yeast multiplying much and, hence, producing diacetyl. This will ideally negate the need for a diacetyl rest. I just racked the pilsner to the secondary about a week ago and took a sample. I did not detect any off flavors I would attribute to diacetyl. That's not to say there isn't any, but to me it was fine. So, I skipped the diacetyl rest and dropped the pilsner down to cold lager temps without one.

YMMV, but I think this work for me.
 

GilaMinumBeer

Half-fast Prattlarian
Lifetime Supporter
Joined
Jan 23, 2008
Messages
65,437
Reaction score
10,793
This is very yeast dependant. Some yeast throw out more than others.

I find the S-23 to be a low diacetyl producer but, I still do a rest. Life is too short to drink buttered beer.
 

TexLaw

Here's Lookin' Atcha!
Lifetime Supporter
Joined
Sep 19, 2007
Messages
3,672
Reaction score
36
Location
Houston, Texas
If you have diacetyl, you need a diacetyl rest. If you don't, you don't. It is a case by case issue.

If you do do not want to check for diacetyl, or you are not confident in your ability to detect it, go ahead and do a diacetyl rest for a few days or so. Like Revvy said, it is an easy way to ensure better beer.


TL
 

Bobby_M

Vendor and Brewer
HBT Sponsor
Joined
Aug 3, 2006
Messages
25,457
Reaction score
4,623
Location
Whitehouse Station
One word of warning. Diacetyl is difficult to taste when the sample is cold. I encourage you to let a sample warm to near room temp and taste it again.
 
Top