How Does Yeast Make Bread Dough Rise?
Yeasts are microscopic one celled fungus plants. A whole yeast plant, when viewed under a microscope, looks like a tiny potato. Great numbers of yeast cells, in the form of a paste, are mixed into bread dough.
In the moist dough, the yeast cells grow and multiply rapidly. As they grow, they release a tasteless gas that bubbles up through the dough, causing it to rise and become light. The many holes you see in a slice of bread are made by the gas bubbles released by the yeast cells. Bread made without yeast is dry and hard, and heavy.
Yeast works by consuming sugar and excreting carbon dioxide and alcohol as byproducts. In bread making, fermentation helps to strengthen and develop gluten in dough and contributes to incredible flavors in bread.
The essentials of any bread dough are flour, water, and of course yeast. As soon as these ingredients are stirred together, enzymes in the yeast and the flour cause large starch molecules to break down into simple sugars. The yeast metabolizes these simple sugars and exudes a liquid that releases carbon dioxide and ethyl alcohol into existing air bubbles in the dough.
If the dough has a strong and elastic gluten network, the carbon dioxide is held within the bubble and will begin to inflate it, just like someone blowing up bubblegum. As tinier air cells fill with carbon dioxide, the dough rises and we’re on the way to leavened bread.