temp shift timing on cold crash

[jkovac]

I've seen a lot on here regarding cold crashing but haven't found anything on this exact topic. Does anyone have any input on the timing of the temperature shift from fermentation stage to cold crash? Do you just dial the temp down and let it get cold as quickly as possible, or do you do a slow shift from fermentation temp to cold crash temp over, say, a few days?

 

[EuBrew]

As long as you're sure fermentation is complete just throw er in the fridge.

 

[mkeckjr]

There are some experimental results from the White/Zainasheff "Yeast" book that says you probably don't want to go too fast. Yeast are apparently sensitive to fast temperature shifts in either direction, and I believe they found that cold crashing faster increased ester formation and diacetyl content. I wish I had the book in front of me right now so I could give the exact results of the experiment, but I don't.

Although anecdotal, just to put a number to it, I personally aim for a crashing schedule of 10 degrees F per 24 hours, aiming for a final temperature of 34 F.

 

[NTexBrewer]

Another thing to consider is if you are using a small fridge as your fermentation chamber it can be hard on the compressor to go from 70 degrees to 40 degrees.

This is the main reason, I usually cold crash over a time period to prevent my fridge coils from freezing up.

I usually do 2 gallon batches in 2.5 gallon Anchor Glass Pickle style jars. If I have room in my Beer Fridge, I just stick it in there.

 

[jkovac]

Thanks all for the replies. I am gonna go with a three-day shift from 70 to 35.

 

[WoodlandBrew]

There are some experimental results from the White/Zainasheff "Yeast" book that says you probably don't want to go too fast. Yeast are apparently sensitive to fast temperature shifts in either direction, and I believe they found that cold crashing faster increased ester formation and diacetyl content. I wish I had the book in front of me right now so I could give the exact results of the experiment, but I don't.

If you do find this I'd like to know. After fermentation completes yeast build up their glycogen reserves, the cell membrane becomes less pliable, and their metabolism slows down. I would be surprised if there is any significant ester production or thermal shock excretion at this point.

 

[mkeckjr]

If you do find this I'd like to know. After fermentation completes yeast build up their glycogen reserves, the cell membrane becomes less pliable, and their metabolism slows down. I would be surprised if there is any significant ester production or thermal shock excretion at this point.

Woodland: when you said "find this" I wasn't sure if you meant if I find the passage in the Yeast book, or if the original poster finds this effect in their beer. However, I tried to do my due diligence, and found the passage in the text to which I was referring. It is at the bottom of page 114 under the "Lagering" section of Chapter 4, "Fermentation". The quote specifically says:

Many people ask if they can crash the beer temperature, or should they lower it slowly? The concern comes over sending the yeast into a dormant state, thereby preventing them from continuing the uptake of compounds during the long cold-conditioning periods. The reality is that very little happens once you take the yeast below 40 F (4 C). If you want the yeast to be active and to carry on reduction of fermentation by-products, it happens much faster at higher temperatures. As far as yeast activity goes, crashing the temperature or lowering it slowly makes little flavor difference if you are dropping the beer below 40 F (4 C). However, very rapid reduction in temperature (less than 6 hours) at the end of fermentation can cause the yeast to excrete more ester compounds instead of retaining them. In addition, if you plan to use the yeast for repitching, you should avoid very rapid temperature changes (up or down) as they can cause the yeast to express heat shock proteins.

Unfortunately there is no supporting evidence to this statement, nor is there a reference, so I was wrong about experimental results.

Side note: I'm in Medford; it's been a rough brew season so far this year. I enjoy your blog, thanks for all the effort there.

 

[BigFloyd]

Once fermentation is well and truly complete (stable FG 4-5 days), I simply move the primary over to the lagering upright freezer (set at 35*F).

I strive to be very precise when it comes to optimal temps (mash, pitch and ferment) for whatever I'm brewing. Having done this "fast crash" many times with no discernible flavor issues, however, I won't hesitate to continue doing so with all batches (lagers, ales and ciders).

 

[WoodlandBrew]

Thanks for finding that mkeckjr. I could see how there may be some thermal introduced excretion if the yeast was still active. Considering that this is from the lagering section that might have been the case. I poked around for papers that might have evidence of thermal related ester excretion that is mentioned, but couldn't find anything. It is well documented that ester production changes with temperature.

It's been a brutal winter this February. The snow backs on my walk way are over my head. If your brewing outside or in your garage in Medford I feel for you. ... But it is good basement lagering weather

 

[jahdub]

Maybe my reading comprehension is poor, but that snippet reads to me like they're saying it isn't really a big deal. Obviously we don't want to crash before the yeast have finished cleaning up. I don't consider repitching yeast to be of any value, so that aspect wouldn't bother me. Harvesting from starters is cleaner and easier.

Also, with a simple fermenter in chamber type crashing setup, I doubt it chills terribly quickly. 5 gallons takes a while to cool.

 

[mkeckjr]

I think at the end of the passage that is quoted it says that very rapid shifts (less than 6 hours) from fermentation temperatures to lagering temperatures may cause excretion of more esters, as opposed to the expected reduction in esters. Again, this is unsubstantiated in the text, so who knows where this information is coming from as far as a technical reference. Further, I think it would be pretty hard to crash a 5+ gallon batch that fast with the tools homebrewers traditionally use. I ferment in a chest freezer, and have a tough time chilling more than 20 F in a day, so I think, while possible, for most homebrewers it is unlikely to experience this fast of a shift.