On Food and Cooking

Freezing Once the mix has been prepared, it’s
prechilled to speed the subsequent freezing.
It’s then frozen as rapidly as possible in a
container with coolant-chilled walls. The mix
is stirred to expose it evenly to the cold walls,
to incorporate some air, and above all to
produce a smooth texture. Slow cooling of an
unstirred mix — “quiescent cooling” —
causes the formation of relatively few ice
crystals that grow to a large size, grow
together into clumps, and give a coarse, icy
texture. Rapid cooling with stirring causes the
quick production of many “seed” crystals
which, because they share the available water
molecules among themselves, cannot grow as
large as a smaller population could; the
agitation also helps prevent several crystals
from growing into each other and forming a
cluster that the tongue might notice. And
many small crystals give a smooth, velvety
consistency.