Fact & Fable

Churning turns cream into butter by making its tiny milk-fat globules join together. Cream begins as fat dispersed through a watery liquid. As it is agitated, the fat gathers into visible grains and clumps, while liquid called buttermilk separates out. This rearrangement is called phase inversion. In cream, fat droplets sit within a continuous watery phase; in butter, fat forms the continuous structure and small water droplets are dispersed through it. Churning therefore changes how the existing fat and water are arranged, rather than creating fat from nothing. The butter grains are then worked together into a cohesive mass, helping remove more buttermilk. Salt may be added before packing and chilling. Temperature also matters: the balance between solid fat crystals and liquid fat affects how firm and spreadable the finished butter becomes. Source: University of Wisconsin Center for Dairy Research .