Cold Crashing clarifies cider by causing the yeast to clump together, or "flocculate." These clumps of yeast then fall out of suspension much faster than individual cells (due to some fluid dynamics that I won't pretend to understand). Flocculation depends on many factors, chief among them, yeast strain, but temperature plays a major factor. For the majority of yeasts, a decrease in temperature induces flocculation, although the ideal temperature for flocculation depends on the strain.

As a side note, aging beer at cold temperatures also causes proteins to bond to polyphenols and form a "chill haze," which precipitates readily.

If you're curious, other factors that can affect flocculation include pH, calcium concentration, ethanol concentration, as well as presence of certain "inhibiting" sugars (glucose, mannose, maltose, and others).

Cold Crashing clarifies cider by causing the yeast to clump together, or "flocculate." These clumps of yeast then fall out of suspension much faster than individual cells (due to some fluid dynamics that I won't pretend to understand). Flocculation depends on many factors, chief among them, yeast strain, but temperature plays a major factor. For the majority of yeasts, a decrease in temperature induces flocculation, although the ideal temperature for flocculation depends on the strain.

As a side note, aging beer at cold temperatures also causes proteins to bond to polyphenols/tannins and form a "chill haze," which precipitates readily.

If you're curious, other factors that can affect flocculation include pH, calcium concentration, ethanol concentration, as well as presence of certain "inhibiting" sugars (glucose, mannose, maltose, and others).