Visual Guide - Sublimation
Sublimation Explained
Sublimation is the phase change that makes freeze drying possible: ice turns straight into vapor without first becoming liquid water, and it happens while the food stays frozen.
In Plain Language
Most water changes state in the order you expect: heat ice and it melts into liquid, heat liquid and it boils into vapor. Sublimation is the shortcut. Under the low pressure inside a freeze dryer, the ice in fully frozen food can pass directly from solid into vapor. The frozen water leaves the food as gas, and the food never puddles or boils on the way out.
This is why freeze drying keeps the food frozen through the whole drying phase, and why the machine carefully manages both temperature and pressure: hot enough to drive the ice out steadily, low enough that the ice sublimates instead of melting.
The practical result is a dry product that keeps its shape: because the water leaves as vapor rather than draining as liquid, the food structure stays mostly in place.