Lagering...why drop the temp slowly?

[Goetinger]

Hello all,

I have heard from several sources to drop the temperature slowly when lagering. What is the purpose?

I have a pilsner that fermented for 3 weeks, a diacetly rest for 2 days, and is now back in the cooler at 45 degrees. I cant get it any colder. I can bottle the beer and store the bottles in the fridge, but I obviously can not drop the temperature slowly. What is the purpose for this?

Does anyone lager in the bottles? Do I need to leave the bottle at 55 degrees after priming to allow the bottles to prime?

 

[day_trippr]

The slow temperature descent is to not stun the yeast into torpor...

Cheers!

 

[Goetinger]

forgive me for my ignorance. What is torpor?

 

[BigFloyd]

I'm still waiting to see any valid brew science to back up the idea that it's somehow detrimental to drop the temp quickly after fermentation has completed and the yeast have gone into dormancy. Maybe because it can be bad for yeast health to have sudden temp fluctuations while they are engaged in the fermentation process, someone jumped to the erroneous conclusion that it's always bad no matter when.

Don't worry about it. I cold crash everything (including lagers) by simply taking the primary out of the fermenter chamber and putting them in the lagering freezer (at 35*F). The temp drops about 30*F over a period of hours. I'm not picking up any sort of unwanted flavors from the practice and I often harvest/reuse the yeast afterwards.

 

[Goetinger]

Thanks bigfloyd. Do I need to carb the bottles at room temp after bottling?

 

[BigFloyd]

Thanks bigfloyd. Do I need to carb the bottles at room temp after bottling?

Yep. For bottle carbed beer that hasn't already been through cold lagering, you'll want to first let them carb up a few weeks at room temp. and then store them in the cold several weeks.

 

[hunter_le five]

I've tried it both ways (cold crash vs gradual temp drop), and there wasn't a discernible difference to me. Not that my taste buds are particularly discerning, so take that with a couple handfuls of salt. YMMV.

 

[TyTanium]

If you did a D-rest, then there's no harm in dropping the temp fast. The yeast are done.

The slowly-dropping is necessary in more traditional lagering where you start dropping to lagering temp when you're a few points above final gravity, and the yeast continues to work well into the lagering process to eat up those last few gravity points.

 

[BigFloyd]

If you did a D-rest, then there's no harm in dropping the temp fast. The yeast are done.

The slowly-dropping is necessary in more traditional lagering where you start dropping to lagering temp when you're a few points above final gravity, and the yeast continues to work well into the lagering process to eat up those last few gravity points.

That's good to know since I just today took a Maibock that had been d-resting about a week at 63*F (and was stable at FG) and moved it to the lagering freezer which is set at 35*F where it will sit for a week until the time to keg it for the long, cold sleep.

 

[Goetinger]

Thanks for the feedback.

Do you need to carb a lager at lager temp, or is room temp OK? Corn sugar or DME?

 

[Cyclman]

Carbing should always be at about 70 degrees, sugar, DME, honey, lots of ways to add sugar to carb.

The theory of slow temp reduction is to keep the yeast active, but IMO if you're lagering below 40 the yeast aren't very active anyhow. I actually like to drop temps slow and lager at 40 for this reason. Takes longer, never tried a side-by-side comparison. I have a huge pipeline, so an extra month lagering doesn't hurt much.