Why Drop Temperature Slowly?

[murphyslaw]

When lowering the temp of a beer post-fermentation—whether it be cold crashing an ale, a soft crash before dry hopping a NEIPA, or lagering after the diacetyl rest—brewers sometimes recommend doing so slowly (3-5 degrees a day, or whatever). I know not everybody does it, but what is the downside to just doing it as fast as you can?

I’ve never really under that and I’m wondering what I’m missing.

 

[passedpawn]

When lowering the temp of a beer post-fermentation—whether it be cold crashing an ale, a soft crash before dry hopping a NEIPA, or lagering after the diacetyl rest—brewers sometimes recommend doing so slowly (3-5 degrees a day, or whatever). I know not everybody does it, but what is the downside to just doing it as fast as you can?

I’ve never really under that and I’m wondering what I’m missing.

I have never done that. I've cold-crashed hundreds of batches, from ale/lager temps right down to 33F overnight. It's probably just some myth that gets perpetuated.

 

[DBhomebrew]

By Palmer. I'm not sure if it's in vol 4 or not.

 

[VikeMan]

I think this idea might be a holdover from olde tymes when things like diacetyl cleanup were actually happening during a slow ramp down to lagering temps. IMO and IME, if the yeast have done everything they need to do fermentation and cleanup-wise, it's fine to crash at full speed. By full speed I mean set the fridge to lagering temp in a single step. The temp of the fridge will drop pretty quickly. The beer will take longer.

 

[TyTanium]

Ditto passedpawn. There are places for tight controls. Chilling finished beer isn't one of them for me.

 

[day_trippr]

If you narrow the scope of the question to lagering there might be some yeast health challenge invoked by a legit crash vs a slow ramp...

Cheers!

 

[murphyslaw]

If you narrow the scope of the question to lagering there might be some yeast health challenge invoked by a legit crash vs a slow ramp...

Cheers!

Is there? I thought the idea was that you go down to lager temps after fermentation is complete and the yeast is done? This is why I asked

 

[DBhomebrew]

When Palmer mentions it, it's in regard to lipids. According to him, fast crashing may cause yeast to throw lipids which would affect head retention and shelf stability.

Again, I don't know if he's still making the claim in vol 4.

 

[passedpawn]

When Palmer mentions it, it's in regard to lipids. According to him, fast crashing may cause yeast to throw lipids which would affect head retention and shelf stability.

Again, I don't know if he's still making the claim in vol 4.

Palmer has forgotten more than I'll ever know about homebrewing... but ...

It seems brewing is an evolving science. Some of the gospel we learned back in the day (10 years ago!) is now considered silly. This forum, while full of anecdotal evidence, is one HUGE knowledge base and database of experimentation. I'd trust the collective wisdom here before I'd go with any one "expert".

 

[DBhomebrew]

Palmer has forgotten more than I'll ever know about homebrewing... but ...

It seems brewing is an evolving science. Some of the gospel we learned back in the day (10 years ago!) is now considered silly. This forum, while full of anecdotal evidence, is one HUGE knowledge base and database of experimentation. I'd trust the collective wisdom here before I'd go with any one "expert".

Of course. I'm just pointing out that it's not some random Internet myth. As I noted twice, I don't even know whether Palmer still subscribes to the thought.

Besides, I don't have a dog in the fight. I ferment at ambient with seasonal temp control.

 

[CascadesBrewer]

Of course. I'm just pointing out that it's not some random Internet myth. As I noted twice, I don't even know whether Palmer still subscribes to the thought.

It is recommended in the 4th Edition of "How to Brew" on page 174 in regards to lagering:

"...slowly reduce the temperature by not more than 10F (6C) a day down to about 35F (2C). Gradually cooling ensures the yeast cells don't go into thermal shock and excrete lipids that can cause off-flavors and hurt head retention."

Is it true? I don't brew lagers myself. I often cold crash dry hopped ales and I drop the temps fast. In other cases, I keg a room temp ale then move it directly into my fridge. I have not noticed a problem, especially not one big enough for me to add 4 to 5 days to my fermentation schedule.

 

[passedpawn]

It is recommended in the 4th Edition of "How to Brew" on page 174 in regards to lagering:

"...slowly reduce the temperature by not more than 10F (6C) a day down to about 35F (2C). Gradually cooling ensures the yeast cells don't go into thermal shock and excrete lipids that can cause off-flavors and hurt head retention."

Is it true? I don't brew lagers myself. I often cold crash dry hopped ales and I drop the temps fast. In other cases, I keg a room temp ale then move it directly into my fridge. I have not noticed a problem, especially not one big enough for me to add 4 to 5 days to my fermentation schedule.

The Yeast book (Chris White and Jamil Z) mentions rate of cooling in the lagering chapter. They say that when lagering, ideally the yeast is left ABOVE 40F so that the yeast can continue to work on any sugars that are left, as well as further conversion of byproducts of fermentation. Below 40F, the yeast are dormant. They recommend lowering the temperature gradually so that the yeast don't go dormant through some sort of shock.

They state that if you're not lagering, and if you're crashing below 40F, "crashing the temperature or lowering it slowly makes little flavor difference". If you have the book, check for yourself in Fermentation Endgame > Lagering chapter.

 

[murphyslaw]

Ah, perfect. I do have the Yeast book. I'll go back through that tonight. I knew I read it somewhere "authoritative."

But that all makes sense. I almost exclusively brew ales and generally don't bother with the slow ramp. But I plan to brew more lagers and its helpful to know.

 

[murphyslaw]

This is from Craft Beer and Brewing regarding lagers:

When moving from primary fermentation to lagering, it's a good idea to rack your beer to a secondary fermentor, even if you don't normally use one for ales. Then, gradually cool your beer down to lagering temperatures over the course of a few days. About 2-4°F (1-2°C) per day is ideal. Avoid a sudden temperature drop, which could shock the yeast remaining in suspension and cause it to become dormant.

One of the amazing things about lager yeast is that it continues to slowly work even at temperatures near freezing. As the beer lagers, yeast cells continue to mature the beer and remove undesirable flavor compounds. Anheuser-Busch, the largest brewer of lagers in the world, uses Beechwood chips not for flavor, but rather to provide more surface area for yeast cells to settle and remain in contact with the maturing beer.

 

[VikeMan]

The Yeast book (Chris White and Jamil Z) mentions rate of cooling in the lagering chapter. They say that when lagering, ideally the yeast is left ABOVE 40F so that the yeast can continue to work on any sugars that are left, as well as further conversion of byproducts of fermentation.

They seem to be assuming that someone would be starting to lower the temperature before attenuation is finished and before diacetyl has been cleaned up. But who does that anymore? I suppose lowering the temp slowly could be insurance, in case attenuation/cleanup were not finished. But to me, that seems to be a long drawn out solution to a problem created by rushing in the first place.

Below 40F, the yeast are dormant. They recommend lowering the temperature gradually so that the yeast don't go dormant through some sort of shock.

Well, yeast going dormant, and falling out of suspension, is one of the reasons we lager. I want the yeast to go dormant.

ETA: I just rememberd this, from KU Leuven's brewing science certificate course:
"Typically, after fermentation, temperature is slowly lowered to the lagering temperature. This is done so that yeast cells can remove diacetyl. So during the first step of this cold conditioning, there is some quite important yeast activity."

Again, diacetyl. And an assumption that there still is some left to remove.

 

[malter]

My process for lagers includes dropping the temperature as quickly as possible.

I ferment at 50F until the krausen has fallen and things are slowing quite a bit (1 week or so. I then move the fermenter to my basement (ambient about 65F) and let the fermentation finish (2-3 more weeks). This is my diacetyl rest. Following that, I keg and crash to 35F as quickly as possible. I've used two yeasts in my quest for the perfect lager (34/70 and S23) and both finish very nicely this way.

After a month at 35F, the beer tastes great! I usually have about 1 pint of yeasty beer and then the beer turns bright. The attached photo shows a recent Czech Pilsner I did this way. No fining agents.