On Food and Cooking

The structure of butter, which is about 80%
milk fat and 15% water. The fat globules,
solid crystals, and water droplets are
embedded in a continuous mass of semisolid
“free” fat that coats them all. A high
proportion of ordered crystals imparts a stiff
firmness to cold butter, while free fat lends
spreadability and the tendency to leak liquid
fat as it warms and softens.
Cultured cream butter, the standard in
Europe, is the modern, controlled version of
the commonest preindustrial butter, whose
raw cream had been slightly soured by the
action of lactic acid bacteria while it slowly
separated in the pan before churning. Cultured