Crust formation

Crust formation is the drying and setting of a baked good's surface as water evaporates and the surface heats.

Crust formation: A round loaf of crusty bread with a dry, crisp, golden-brown surface and a cracked top.
  • Food science and baking chemistry

A crust is formed as water evaporates from the surface and leaves it dry. Evaporation also lowers the product's weight.

As long as water continues to evaporate off the crust, the surface stays cool, because evaporative cooling holds the temperature down. Once evaporation slows significantly, surface temperature rises quickly above 300°F (150°C), and the high heat breaks down sugars and proteins on the surface.

Steam can postpone this. Baking breads with steam injected into the oven slows crust formation by delaying the drying of the surface, and that allows the bread to continue rising. The timing matters in other products too: in cake doughnuts, if carbon dioxide releases too slowly, the crust sets before leavening occurs.

Related entries

Sources

Written by VanillaGoods in our own words from these sources. Last reviewed October 15, 2026.

  1. The Baking Process, ckbk reference library: Professional Cooking, 8th Edition (Wayne Gisslen)
  2. Caramelization and Maillard Browning Occur on Crust, ckbk reference library: How Baking Works (Paula Figoni)