According to "How to Brew" by John Palmer (4th ed.), cold conditioning (a.k.a. lagering) is the act of cooling beer after fermentation has completed (including maturation) in order to clarify the beer. So far so good.
The book also suggests to slowly decrease the temperature (down to 1 °C/day!) to avoid thermal shock on the yeast:
The point of slow cooling is to prevent thermal shock of the yeast and subsequent excretion of fatty acids and other lipids. These lipids can interfere with head retention and will readily oxidize, creating stale flavors. Thermal shock at any time can cause the yeast cells to release protein signals that cause other yeast cells to shut down to protect against the cold, potentially leading to premature flocculation and underattenuation.
However, everyone seems to cold crash, and I did not find other sources supporting this claim. Is there any evidence? Am I missing something?
I am also not sure whether this would also be relevant for pitching temperature since, for instance, the rehydration temperature for dry yeast is usually higher than fermentation temperature.
... last but not least, such method definitely makes the overall process 1-2 weeks longer, which is pretty annoying.
