Welcome to my first ingredient spotlight as part of the Baking Essentials section of this site. I’ll be highlighting common baking ingredients individually in an attempt to learn more about the science of baking and the role each ingredient plays in the bigger picture. Let me just add a quick disclaimer that I am not an expert. I’m just a gal with a library card and a desire to learn. If you have any insights you’d like to share, please leave a comment!
Flour seems simple enough. We use it all the time in baking and in fact, recipes without flour are in the minority, which is why I chose it for my first spotlight. Do you really know what flour is and why we use it? I’ve learned that it’s anything but basic (in fact I think I started with the hardest ingredient). I’ve done the homework for you, done my best to wrap my brain around the science of it and attempted to sum it up in a concise and accessible format. We’ve got a lot of ground to cover, so let’s get started!
What is Flour
Standard flour comes from the berry of the wheat grain. The wheat berry, or kernel, is composed of three parts. The outer layer is known as the bran and the interior is made up of the endosperm and germ. The endosperm comprises most of the kernel and holds all of the starches and proteins. The germ is composed mostly of fat.
White flour is made by grinding only the endosperm into a fine powder. Whole wheat flour is made from the entire kernel— the bran, endosperm, and germ.
How and Why Flour is Used in Baking
It is the proteins “glutenin” and “gliadin” (say those words together 5 times fast) found within the flour that perhaps make it so important to baking. When mixed with moisture they create gluten, something we’ve all heard of. Flour itself doesn’t contain any gluten, but dough does. It is a byproduct of flour manipulated with moisture. The gluten bonds in a dough trap gases from yeast fermentation or chemical leaveners and create rise.
Gluten development is determined by mixing time and presence of fat in the dough. The longer a dough is mixed before baking, the more time the gluten bonds have had to form and the more rise they’ll create through trapped gases. Fat actually works to inhibit the strength of gluten because it coats the proteins and weakens the bond it forms within a baked good. Think of a loaf of bread versus a cookie, both have different mixing times and fat content, which among other things, affect the very different end products.
The starches in flour have two roles. They contain enzymes that break down into sugars which provide food for yeast and therefore aid in rise. Starches also work to absorb the moisture during baking and set the finished product through a process called gelatinization, which happens at temperatures above 140 degrees F. The proteins are responsible for volume, texture, and appearance, and the starches hold it in place even after it’s removed from the heat.
Flour is categorized by its protein content and hence its gluten power. Cake flour has the least amount of protein (6-8%) and will create the least amount of gluten, which is why it’s ideal for tender cakes. All-purpose flour, as its name suggests, is best for general baking and is composed of flours with high and low gluten power and has a median protein content of 10-13%. Bread flour has a high protein content (12-15%) and is best for yeast breads.
Whole wheat flour has the highest ratio of protein (13-14%), but the bran and germ that have been milled into it actually work as little knives to cut through the gluten bonds and inhibit rise. Because of this wheat flour is often used in conjunction with other flours, such as all-purpose, to compensate.
Of course flour can be made from any grain and from many other foods as well. Some examples include rye, potato, corn, spelt, and nut flours. None of these contain gluten-forming proteins and are either blended with a high-protein wheat flour for baking, or other leavening methods are employed.
Self-rising flour is all-purpose flour that has been combined with salt and a chemical leavener, usually baking powder. Since the chemicals lose their leavening ability over time, and recipes call for different ratios of flour to leavener, self-rising flour is not recommended for use. Whenever I see it in recipes I always substitute 1 scant cup all-purpose flour, plus half teaspoon salt, plus 1 ½ teaspoons baking powder for 1 cup self-rising flour.
Flours bleach naturally over time through oxidation and the aging of the flour actually enhances its gluten-forming potential and flour strength. But because it can be a time-consuming process, chemicals are often used instead to simulate the results. Not only can these chemicals affect the flavor of the flour, but they can also destroy some of its nutritional value. Look for “unbleached” on the label to avoid flours aged with chemicals.
How to Measure Flour
I actually already have a post dedicated to this topic. Click to read how I measure flour.
How to Store Flour
Flour does not have an indefinite shelf life. It can absorb moisture in the air and odors from its surroundings. Its best to store it in an air-tight container in a cool, dry place such as a pantry for a period of up to 6 months. Since whole wheat flour contains fat, it could go rancid and should be refrigerated if storing for more than a few months.
So now you know more than you could have ever wanted to know about flour. It is fascinating in a way though, isn’t it? Hopefully this insight will help you understand what’s happening when you bake that loaf of bread or pan of brownies. Do you have a question or something to add? I’d love for you leave it in the comments.
“Bakewise: The Hows and Whys of Successful Baking” by Shirley O. Corriher
“I’m Just Here for More Food” by Alton Brown
“On Baking” by Sarah Labensky, Eddy Van Damme, Priscilla Martel, and Klaus Tenbergen
“Baking and Pastry Fundamentals” by Johnson and Wales University