John Palmer recently posed an experiment to the gentleman who does the brulosophy channel. John Palmer believes that you get better head retention by slowly dropping the crash temp instead of giving the yeast a thermal shock overload by setting the crash temp all at once. I believe it was 3 Celsius per 12/hrs. day until you reach crash temp. There is a video on youtube https://www.youtube.com/watch?v=sErHEhkF1M0
John and I discussed this a few years ago, so I started trying it. I found no difference.
The hypothesis was that yeast cast off certain things if subjected to a quick temperature drop, but less so if it is gradual. I don’t have the equipment to crash it as fast as a glycol chiller might drop it, so I just dial down the freezer and let it work out the drop on its own…it takes a day or so to get it down to 32-34F (5 gallon batch from fermentation temperature to just above freezing) and that seems to work fine for me.
I don’t have a problem with suck back. Once the beer is finished, I do a D rest in the fermenter (if needed, normally it doesn’t) and then do a closed transfer to a CO2 purged keg. I then cold crash while having CO2 pressure on the keg. If I have to add gelatin to clear the beer, I keep a slight positive pressure on the keg when I open the lid to add the gelatin. This helps minimize O2 pickup in the keg and prevents suck back when I open the keg. It is a simple solution and works well for me.
Good answer to my question, thanks! That was what I was getting at- if the beer is going to cold crash in the keg anyway, why do it in the fermenter too? I guess you’re putting slightly less sediment in the keg, but I would think the amount would be miniscule.
How about adding gelatin to the beer once it’s carbonated? Does it work the same? Any drawbacks?
I usually add it (when I do) to the keg before it gets fully carbonated. I just add a few pounds of CO2 to prevent oxygen ingress crash and add the gelatin. Have never done it if the beer is fully carbonated as I fear it may foam because of the differences in temperature between the two liquids
The “certain things” are lipids
Cooling too rapidly may also cause the yeast to express heat shock proteins. Those will not affect the current beer, but if you harvest the yeast and use it again the new batch will be affected.
You guys know well enough, so thanks for the clarification - I didn’t want to go back through the segment for John’s specific descriptors - at one point I think he also mentioned “wax” or “wax-like substances”, too, but maybe that was just a more descriptive form for lipids. In any event - agreed on your points and maybe the worst effects are downstream in later batches of repitched yeast and not so much on the initial cold crashed batch.