Crashing or slowly cooling?

[Jakeedward]

I notice in the latest "How to Brew" edition (4th edition) it talks about slowly reducing the temperature to cold condition beer. Apparently (page 95) slowly cooling the beer instead of crashing "prevents thermal shock of the yeast cells and subsequent extraction of fatty acids and lipids" which can "interfere with head retention and will readily oxidise causing stale flavours".

On that page, it suggests cooling the beer by 2F (1C) per day. However, in the "How to Brew Lager Beer" section (page 174) it suggests cooling the beer by 10F (6C) per day. I can only assume that this difference means that ale should be reduced by 2F per day, and lager by 10F by day (although not sure why).

This seems to be in conflict with the suggestion in the very detailed "Yeast" book by Chris White and Jamil Zainasheff, where on page 114 it states that "crashing the temperature or lowering it slowly makes little flavour difference if you are lowering it to less than 40F (4C). Instead, it suggests that slow temp reduction is just a traditional lager conditioning technique that's not really used anymore where continual fermentation was desired at lower temps.

Does anyone know of any scientific studies that indicate whether slow temp reduction is actually beneficial/required? If not, it's a lot easier for me to crash. I currently crash both ale and lager to about 3C (37F), which takes about 2 days for ale (starting from diacetyl rest temp of 25C (77F)).

 

[day_trippr]

This is the first I've even read about the potential effects of "too rapid" a crash wrt a non-lagered beer.
If Dave didn't provide something substantial to back that up I would dismiss it in favor of Chris & Jamil's take.

It takes almost 48 hours for one of my fridges to drop 10 gallons of beer from ~68°F to 34°F, so ~ 0.7°F/hour.
I frankly doubt that ponderous slope is going to do anything at all to the yeast aside from eventually numbing them to sleep.

And wrt any maladies from that practice, I have the last ~gallon and a half from a batch of neipa brewed in late February still on tap and it still tastes and looks wonderful. That's over four months in the keg with no browning or loss of hop character at all.

Keeping O2 out of the cold side has to be far more important...

Cheers!

 

[Jakeedward]

This is the first I've even read about the potential effects of "too rapid" a crash wrt a non-lagered beer.
If Dave didn't provide something substantial to back that up I would dismiss it in favor of Chris & Jamil's take.

It takes almost 48 hours for one of my fridges to drop 10 gallons of beer from ~68°F to 34°F, so ~ 0.7°F/hour.
I frankly doubt that ponderous slope is going to do anything at all to the yeast aside from eventually numbing them to sleep.

And wrt any maladies from that practice, I have the last ~gallon and a half from a batch of neipa brewed in late February still on tap and it still tastes and looks wonderful. That's over four months in the keg with no browning or loss of hop character at all.

Keeping O2 out of the cold side has to be far more important...

Cheers!

Thanks!
What do you mean by keeping O2 out of the cold side?

 

[day_trippr]

It means not allowing any oxygen into the beer post fermentation all the way to the final package. That means avoiding the use of "secondary" fermentors, preventing O2 ingress during cold-crashing, and purging kegs and transfer lines before racking (or bottles and transfer lines). One can even go more extreme (eg: carbonation via "spunding" instead of force-carbonation using bottled CO2, using specific barrier-type tubing for both beer and CO2, etc) with positive if diminishing benefits.

That O2 degrades beer is inarguable, while Mr. Miller's posit already has counters, so I'd put my efforts where the benefit is well known...

Cheers!

 

[Jakeedward]

Thanks again!
I don't use secondary fermentors. I purge kegs, but not the thin transfer line (perhaps I should).
During cold crashing, I simply turn down the temp on the fermentation fridge. The airlock is a tube from the top of the fermentor into a mug filled with Star San. Do you see an issue with this? I notice in other threads that some people cold crash in kegs to prevent the contraction of liquid sucking in any O2.

Cheers!

 

[Jakeedward]

BTW, How to Brew is by John Palmer, not Dave Miller.

 

[day_trippr]

Aw, crap, you're right of course. My bad. Incipient senility, I reckon

The potential issue with the tube-in-Star San thing (and it has bitten quite a few folks) is the dreaded "Star San Suck-Back". As the fermentor temperature drops it creates a negative pressure therein which can easily suck a lot of Star San into the fermentor. Folks have gone to racking to kegs while there are still a handful of fermentation points remaining, some using a spunding valve, others just going by dead-reckoning. Others are using CO2-filled balloons instead of the tube thing. I apply very light CO2 pressure (0.4 psi) directly to the sealed fermentor...

Cheers!

 

[Jakeedward]

Aha, maybe that is the cause of the faint bitter/astringent aftertaste I've been trying to pinpoint.