Bread unpredictable since the steam is not produced until the bread is baked. Steam leavening happens regardless of the raising agents (baking soda, yeast, baking powder, sour dough, beaten egg white) included in the mix. The leavening agent either contains air bubbles or generates carbon dioxide. The heat vaporises the water from the inner surface of the bubbles within the dough. The steam expands and makes the bread rise. This is the main factor in the rising of bread once it has been put in the oven. CO generation, on its own, is too small to account for the rise. Heat
Bread machine Bread machine A bread making machine or bread maker is a home appliance for turning raw ingredients into baked bread. It consists of a bread pan (or "tin"), at the bottom of which are one or more built-in paddles, mounted in the center of a small special-purpose oven. This small oven is usually controlled by a simple built-in computer using settings input via a control panel. Most bread machines have different cycles for different kinds of dough—including white bread, whole grain, European-style (sometimes labelled "French"), and dough-only (for pizza dough and shaped loaves baked in a conventional oven). Many also