Is diacetyl rest necessary for lagers?

[Andreas]

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]

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]

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.

 

[Revvy]

REad this thread an make up your own mind...

https://www.homebrewtalk.com/f13/preventing-diacetyl-hold-butter-please-70438/

They way I figure is a week (or so) of prevention is worth a pound (or 5 gallons) of unbuttered beer.

 

[TexLaw]

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]

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.