The Food Lab: Better Home Cooking Through Science

respect)†. When flour is mixed with liquid, two proteins
naturally present in wheat, glutenin and gliadin, link
together to form the resilient, stretchy protein matrix known
as gluten. In leavened breads, air bubbles are formed in this
matrix and expand, creating the familiar hole structure
inside a loaf of bread (or a good pizza crust, for that matter).
With traditional or “slow” breads, that leavening agent is
a living fungus called yeast. As the yeast consumes sugars
present in the flour, it releases carbon dioxide gas, forming
thousands of teeny-tiny air pockets inside the dough and
causing it to rise. Once you pop that dough into the oven,
those air pockets heat up and further expand, and a
phenomenon known as oven spring takes place. Finally, as
the gluten and starches get hot enough, they set into a
semisolid form, giving structure to the bread and turning it
from wet and stretchy to dry and spongy.
The only problem with yeast? It takes a long, long time to
work. Enter baking soda. Unrestricted by the protracted time
frames of biological organisms, it relies instead on the quick
chemical reaction between an acid and a base. Baking soda
is pure sodium bicarbonate—an alkaline (aka basic) powder.
When dissolved in liquid and combined with an acid, it
rapidly reacts, breaking down into sodium, water, and
carbon dioxide. Just as with yeasted breads, this carbon
dioxide expands upon baking, leavening the gluten protein
matrix. This type of chemically leavened bread is referred to
as a quick bread, a broad category that includes everything
from scones and biscuits to banana or zucchini bread and
even pancakes.
Of course, for baking soda to work, a recipe needs to