I know Stone cold conditions their ales, and I’m sure other breweries do something similar.
I’d like to get to the point that I cold condition my ales for a week or two, but these days I’m just desperate to have homebrew on tap again and don’t wait.
The only issue I can see is if you are cold crashing in a carboy or bucket using an airlock. As the headspace cools down, the air in the headspace contracts pulling in air though your solution in the airlock and into the carboy. Now, as stated on other threads, this may be negligible, but why risk any oxidation if need be?
Obviously, the best way would be to close transfer from your primary into a keg and then cold crash in the keg (racking to another keg if a clearer beer pour is desired). If you can’t do that, then take the Denny Conn route and put some saran wrap over the top of the carboy opening and cold crash that way. I go one step further and use the saran wrap with aluminum foil over top both rubber banded down (I am overkill of course).
If you want to minimize cold crashing time and desire very clear beer, the best route is to cold crash for about 24 -36 hrs then simply gelatin fine as you rack to a keg. Minimal time and clear beer = AWESOME!
There are still cells in suspension. All crashing does is lower the cell count from saturation to a level where it is difficult to see suspended cells with the naked eye. It’s why one can still bottle condition cold crashed beer. One has to filter beer to remove all of the cells.
But when we bottle condition we warm the beer up again.
I’ve always been under the impression that the yeast cells sort of go dormant when we cold crash, even if they don’t all fall out of suspension. I would suspect that dormant yeast cells don’t scrub O2, but I honestly have no idea so appreciate the opportunity to gain a better understanding.