Ice Cream

Why churning matters

Ice cream’s smoothness depends on incorporating air while freezing, in a process called overrun. As the mix freezes, mechanical agitation breaks ice crystals into tiny ones (smaller than 50 microns, undetectable on the tongue) and folds in air pockets that lighten texture. Without churning, the same ingredients freeze into a brick of solid ice — the difference between ice cream and a popsicle.

Major styles

• American (Philadelphia-style) — no eggs; cream, sugar, milk, flavor. Light, milky, scoopable.
• French (custard-style) — egg yolks cooked with milk into a custard before churning. Richer, denser, deeper-flavored.
• Italian gelato — less cream, less air, served warmer (–10 °C vs. –18 °C). Denser and more intensely flavored.
• Frozen yogurt — yogurt-based; tangier, less fat.
• Sorbet — no dairy at all; fruit purée and sugar.
• Sherbet — between sorbet and ice cream; small amount of dairy.
• Soft serve — extruded fresh from a machine at –6 °C with high overrun.

A long history

Iced flavored dairy desserts existed in Persia (sharbat, faloodeh) and Tang-era China centuries before reaching Europe. The modern ice cream form emerged in 17th-century Italy and France with the development of techniques to freeze cream using salt-and-ice baths. The hand-cranked freezer was patented in the U.S. in 1843; commercial production began soon after.

Brain freeze

The headache from eating ice cream too fast (sphenopalatine ganglioneuralgia) is real and somewhat understood. Cold on the roof of the mouth causes rapid constriction of blood vessels, then rapid dilation as warmth returns. The brain interprets the dilation as pain, referred to the forehead. Pressing the tongue against the roof of the mouth speeds recovery.