Bread bakers often release a control that injects steam into the hot oven, or use a water mister to spray the loaves when baking. This is supposed to create a crisp crust. How does making dough wet, crisp it?
From a Vancouver Island fan, Brian
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Steam is often used when making country hearth breads, and it's really only effective during the early part of the baking process before the crust has set. Many bakers feel that the idea of steaming to create sauna-like surroundings is preferable to directly spraying the baking loaves.
The purpose of creating a steamy atmosphere inside the oven is to delay the setting of the crust, so that the loaf has a slightly longer period in which the phenomenon called "oven spring" can take place. This is yeast's final push to lift the dough, before yeast cells die as the temperature of the dough becomes very hot. By delaying setting, the dough can rise a little higher while the crust is still flexible.
A steamy oven also promotes the gelatinization of the starch granules, a process that involves their absorption of water in the presence of heat. A crisp crust begins to form as excess moisture is driven from the swollen starch granules on the surface of the loaf. This of course, happens during the latter stages of baking when the atmosphere in the oven is dry. Nuances of flavor also become more apparent and a nice shine develops on the crust as starches on the surface set and the browning process begins.
The above information is just one more example of the complex and fascinating realm of making yeast breads.
Wishing you well as you create crisp crust and fine breads,
Anne and Sue