Ever wonder what makes bread rise? (I mean, other than the obvious answer: yeast.) But HOW exactly does yeast—or perhaps another leavening agent—cause bread to rise, you ask? I’ll tell you.
First, we’ll talk about yeast. Yeast is a biological leavening agent and is member of the fungi family. As it consumes sugars, it releases carbon dioxide. When that carbon dioxide gets trapped inside a structure made out of gluten (we’ll talk more about gluten momentarily), the bread rises. Applying heat to the bread adds a bit more to the rise and also causes it to become a semi-solid, which is what we recognize as bread.
Most flours contain a protein called gluten, that—when mixed with a liquid—forms the structure for a ‘risen’ product. Wheat, barely and rye contain gluten. Other flours, such as oat or almond, do not. Caveat: unless a product is marked ‘gluten-free’ it may still contain trace amounts of gluten from other foods processed in the same area or using the same equipment. Gluten is incredibly important in the rising process, which is why gluten-free bread products don’t tend to rise as well or have as ‘typical’ a texture as regular bread. Gluten is developed during the kneading process, but even no-knead or lightly kneaded breads will still rise well.
However, yeast breads aren’t the only breads that rise; quick breads—like banana or pumpkin—rise without yeast. Baking soda (sodium bicarbonate) and baking powder are chemical leavening agents used for baking. Baking soda uses a chemical reaction to cause bread to rise. Baking soda, when paired with an acid (like buttermilk, vinegar, citrus), releases carbon dioxide. Applying heat to the product helps the rise and also causes it to become a semi-solid, just like the bread made with yeast. Additionally, baking soda aids in browning (also called the Maillard Reaction) and helps your product have that beautiful golden color out of the oven.
Ever wonder what the difference is between baking soda and baking powder?
Baking powder includes baking soda as well as a powdered acid, which means your recipe doesn’t have to have a separate acid to activate the leavening agent. Generally, baking powders are sold as ‘double acting,’ which refers to the rise created with the release of the carbon dioxide, as well as the rise created by a secondary acid that releases carbon dioxide when heated.
Many recipes call for both baking soda and baking powder, which is probably a little confusing. An easy way to think about it is that you want the best balance of rise and flavor. Baking soda begins working as soon as it comes in contact with the acid, but fizzles out soon after. Adding more baking soda may help the rise, but will negatively affect the flavor. Instead, including baking powder in the recipe as well is a way to add more rising ability to your bread without affecting the flavor. One important thing to remember: they cannot be substituted for each other. Yes, you need them both, and in the amounts specified.
Lastly, mechanical leavening agents, like whipped egg whites, add structure by incorporating air into a product. I know my pancake recipe is much improved when I take the time to separate my eggs and whip the whites.
Now don’t you feel smart? Next month: more on baking! (There’s a lot to know.)
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