Ice Cream

Ice cream is a three-phase system — water, fat, and air — held in dynamic equilibrium by freezing, emulsification, and mechanical aeration. Understanding these three phases and how they interact explains everything about ice cream’s texture, from the silky density of gelato to the airy lightness of soft-serve.

The three phases

1. Water phase (continuous): A sugar solution containing dissolved lactose, milk proteins, and minerals. The sugar lowers the freezing point, which is why ice cream is scoopable rather than solid.
2. Fat phase (dispersed): Cream fat globules coated in MFGM proteins and phospholipids, the same emulsion structure as milk — just frozen.
3. Air phase (dispersed): Bubbles incorporated during churning, stabilized by fat globule membranes and denatured proteins. Air is what makes ice cream light; without it, frozen cream is rock-hard.

Freezing point depression

Pure water freezes at 32°F/0°C. Ice cream mixture, with 12–18% dissolved solids (sugar, lactose, minerals), freezes around 26–28°F/−3 to −2°C. Each 1% dissolved solids lowers the freezing point by roughly 0.1°F. This is the fundamental reason ice cream has texture instead of being a block of ice — at serving temperature, a significant fraction of the water remains liquid, keeping the mixture soft.