Diacetyl and ferm phases

[bmantzey]

I'm working on mastering the art of lagering.

I have a Sam Adams Noble Pils clone, a Bud Like clone, and a Fosters clone in progress now.

The Sam Adams reached a point where the fermentation slowed enough that the krausen fell in, so I decided to do a diacetyl rest.

I did a lot of research on this before doing it, but there are a couple things unclear.

1) Should the diacetyl rest occur right after the primary fermentation is complete?

I brought the beer temp up to 68 for about 2 days, and then put it straight back to 50 for another day.

2) How long after the rest should I wait before racking the beer into the secondary?

I racked it this evening, about a day after the rest. I'm wondering if too much yeast has been removed from the beer for the diacetyl to be cleaned up, or if there should still be plenty of active yeast in the secondary for the yeast to clean up it's mess. Will it take longer now that most of the yeast has been dumped down my bathtub?

3) What now?

I added some dry hops to the secondary, which won't be easy to fish out. Do I let it lager for another week for the dry hops to do their thing? Can I let it sit for longer with the hops in there?

4) What exactly is "lagering"?

This is a term I've heard that seems to indicate a long, colder-than-fermentation temperature, aging phase that occurs before bottling/kegging. How cold? How long?

 

[osagedr]

1. The d-rest should be done with 6 or 8 gravity points remaining. I always start mine at 1.020 or just under; take the beer up to room temp and leave it for a week or so. Lots of people never do a d-rest but I had a couple of d-bombs early and will never risk another one. They're fixable but it's a lot of extra work and affects beer quality IMO.

2. Rack your beer to a secondary when you are sure active fermentation is complete. Extra time in the d-rest will not affect your beer quality so don't cut it too short. Having said that, if you followed proper lager fermentation procedures, you probably don't have any diacetyl. Taste your beer and see if you detect any diacetyl. In your current situation, leave it in the secondary at room temp for a week for peace of mind. As you note, there are still lots of yeast in your beer.

3. Lagers are meant to be cold-conditioned for an extended period. They also typically don't have very big hop aroma/flavour. I've over-hoped lagers in the past by dry hopping for too long. So you will have to get rid of those hops--give them a few days to a week at room temp, then rack to a different carboy, then cold crash. You'll get the hop aroma/flavour you wanted and be sure your d-rest is complete at the same time. You may elect to use gelatin to help your beer clear.

4. Lagering comes from "lagern" which means "to store." Lagering is extended cold aging of your beer, and it is this stage as much as the use of bottom-fermenting yeast that defines a beer as a lager IMO. They say 1 week per 8 starting gravity points. Lager as cold as you can without freezing your beer--most of us go at 32 or just above.

Good luck!

 

[bmantzey]

Okay, what I do is cool my wort down to about 70° and pitch the yeast, then put it directly in the fridge (a large fridge using one of those temperature regulation devices). I figure this gives the yeast a little bit of a warm-boost. I have since read that this works but isn't the best idea because the initial warmer temperature promotes higher diacetyl, which when followed by a drop in temperature, can cause more diacetyl to deal with. As long as I have a high enough yeast count to start out with (from enough starter), pitching cold yeast into cold wort should produce better results that may take an extra half a day to really get fermenting, right?

1. So, at what point would I be only 6-8 gravity points from final? When the krausen begins to fall, before it falls, or a few days after? You're suggesting that the fermentation finish up at a higher temperature? That doesn't seem like the desirable thing to do. I heard fermenting at a higher temperature can cause off-flavors.

2. After having transferred it to the secondary already, will there be enough yeast left in suspension to clean up the diacetyl?

3. I'm planning on kegging, can I do the cold-conditioning in the keg, so that I can avoid an additional transfer? This will be the very first time I will use my new keg system.

4. I'm copying that into my notes file. Thanks!!

 

[osagedr]

1. In my experience, if the krausen has fallen all the way you are a bit on the late side for a d-rest but probably still okay. Gotta catch it when it is starting to fall if you can. You're right, fermenting at a higher temp would be no good, but by the time you hit 1.020, finishing off warmer isn't going to cause you any off flavours, and more importantly, will ensure you don't have diacetyl! I've done quite a few lagers successfully that way.

2. I would think you will still have enough yeast left; only problem would be if you were cold-crashing and the yeast were dropping out. Can't do much but try at this point.

3. Kegging as you plan will be fine IMO.

 

[bmantzey]

Great advice, thanks a bunch!!