Why do pastries rise?

Pastries rise for various reasons, all of which can be attributed to the release of gases during the baking process. Here are the main factors responsible for making pastries rise:

1. Yeast Fermentation: Yeast is a microorganism that feeds on the sugars present in the dough. As yeast consumes sugar, it produces carbon dioxide (CO2) gas and ethanol as waste products. This process is known as fermentation. The CO2 bubbles get trapped within the dough, causing it to rise and become fluffy.

2. Leavening Agents: Chemical leavening agents are often added to pastries to provide extra lift. Common leavening agents include baking powder and baking soda. These agents release carbon dioxide gas when heated, causing the dough to rise.

- Baking Powder: Baking powder is a combination of baking soda, an acid (such as cream of tartar), and a drying agent (usually cornstarch). When baking powder is mixed with water, the acid and baking soda react to produce carbon dioxide gas.

- Baking Soda: Baking soda (sodium bicarbonate) is an alkaline substance that releases carbon dioxide gas when it comes into contact with an acidic ingredient. In pastries, baking soda is often combined with an acid such as buttermilk, yogurt, or lemon juice to initiate the reaction.

3. Steam Expansion: As pastries bake, the moisture content in the dough turns into steam. This steam expands and forces the dough to rise. The crust of the pastry traps the steam, allowing the dough to reach its full height before setting.

4. Gluten Formation: Gluten is a protein found in wheat flour. When dough is mixed, the gluten proteins form long, elastic strands that trap the gases released during fermentation and chemical reactions. This network of gluten strands provides structure to the pastry, allowing it to hold its shape as it rises.

5. Oven Temperature: The temperature of the oven plays a crucial role in how well pastries rise. A hot oven provides the necessary heat to activate the leavening agents and generate steam, causing the dough to expand quickly.

By carefully controlling the ingredients, proportions, and baking conditions, bakers can create pastries that rise perfectly, resulting in light, airy, and delicious baked goods.