Flour is one of those things we take for granted. It's been around in a crude milling form for about 8,000 years or more. Today, at the grocers there are several varieties available for purchase, some in pretty boxes and others in utilitarian sacks. The issue most bakers have is which one to buy and for what purpose.
Flour is generally milled from wheat because wheat is the only grain with the proper proteins that create gluten - the very backbone of bread. Rice, soy, rye, pea and oat flours are all utilized in the manufacture of breads, cookies and cakes, but only the wheat kernel contains what is needed to lock in yeast gas, hold cookies together and give cream puffs their intricate structure.
If you look at a grain of wheat and create a cross-section, then you will see three major components:
- The Germ: the smallest portion of the grain with the most impact filled with fat, vitamins and minerals or "ash." The germ is the "embryo" of the wheat kernel.
- The germ is removed during the milling process for white wheat flours to keep them from becoming rancid during storage due to its high fat content.
- The germ is prized for its health benefits and is included in whole wheat flour and as a stand-alone additive to cereals and sprinkle for yogurt.
- The Bran: comprises about 14.5 % of a kernel of wheat and is the tough, protective outer shell of the wheat kernel.
- Bran is removed during the milling process because it cuts through the gluten, adds a brown color to the flour and is mainly fiber adding little protein to the flour. If you purchase bran on its own, it's very lightweight and feels like tiny shards of brown paper!
- The bran remains in whole wheat flour and is added to many cereals for the health benefits of the fiber, vitamin content and mineral or "ash" content.
- Whole wheat bread, in order to be light in structure, requires a portion of high gluten or bread flour in the formula for the gluten to form.
- The Endosperm: the largest part of the wheat kernel comprising over 82% of the grain itself. It is primarily made up of starches and proteins. The endosperm is the food for the germ or embryo and holds the gluten needed for the structure of our baked goods.
- The proteins found in the endosperm are glutenin and gliadin- these are responsible for that webbing effect that takes place when the wheat flour proteins are developed with liquids.
- Along with the proteins is starch. The starch is broken down by enzymes in the flour, malt and yeast to simple sugars that are then digested by the yeast.
- Many types of bread do not contain added sugars and are marketed as a healthy alternative but in fact do contain "sugars" created by the breakdown of the starches . . . but I digress.
Now that we know the make-up of a wheat kernel, let's put it to good use by finding out what makes the different verities of flour useful and in what capacity.
Wheat flour is classified by the protein content, the method of bleaching and the wheat type the kernels are grown from.
Flour contains carotenoid pigment - the same type of pigment that gives carrots their orange color and makes flamingos pink - which gives the flour a yellow or creamy cast. This goes away slowly with aging the flour a couple of weeks. While processors do not have the luxury of aging flour for long periods of time, they can speed the process by bleaching. The most common method is the application of Benzoyl peroxide thus speeding the process to two days. Aging and bleaching improves the baking qualities of the flour and not all flours are treated the same way.
The soft wheat or low protein flours are used for cakes, cookies and pastry baking. In the store you will see Swan's Down in the red box or Soft as Silk Cake flour brands. Cake flour is milled fine with the removal of the bran and germ; it is then bleached with chlorine gas to give it the light ivory color. This method of bleaching also makes cake flour better able to be hydrated allowing for amounts of liquids to be added to the batter, thus creating high-ratio cakes. The protein content of the cake flour is very low at 7-8%. The gluten in cake flour tends toward vertical movement aiding in the height of cake layers (as a side note, when making a roux, use cake flour in place of all-purpose and you'll see a difference in the amount of liquid it will hold!). You can identify cake flour by its very light color and ability to hold together when pressed together in your hand. It tends to clump and requires sifting before use and is not recommended for broadcasting, as in dusting the bench.
Pastry flour is used for pastries and cookies and has a slightly higher protein content of 9-10%. The milling process is very much the same as cake flour but the bleaching agent is different. This flour is not generally pre-packaged but is usually found only in the bulk section of your grocery store. It is sold by the pound in either whole wheat pastry flour or bleached or unbleached. Azodicarbonamide is used to accelerate the natural bleaching process in pastry flour and bread flours.
If pastry flour was treated in the same manner as the cake flour, the spread of the cookie produced would be inhibited as the gluten in pastry flour tends toward horizontal movement due to the treatment it receives in bleaching. Pastry flour is great for many cookie recipes and for Pate Brisee and Pate Sucree where you want a tender crust that tends not to puff up.
Next we come to all-purpose flour ("AP flour") which is most commonly used in hotels and restaurants. AP flour will run between 10-11% in protein content and will work well for many applications. Used in many home recipes, AP flour has too much protein for commercial cake making and far too little for commercial bread baking. In the grocery store you will find this the dominant flour. King Arthur, Gold Medal, Pillsbury and store brands are available in 4, 5 up to 10 pound bags. AP flour can be identified by its slightly creamier color and sandier texture as compared to cake flour. When you broadcast AP flour it with flow rather than clump. It is great for home use and small restaurants where space is prime.
Bread flour has higher protein content than AP flour but is not the highest. At 11-12% protein content, it has a creamy color and will flow when broadcast. Bread flour can be found at the grocery store and is called for when using a bread machine at home. The higher protein content allows for more development of the gluten creating toothsome, tasty breads. King Arthur, Gold Medal and Pillsbury make bread flour for purchase at the local grocery but you can find it in the bulk department as well.
Clear 12-14% and high gluten 13-14.5% flours are best suited to bread making and give free-form hearth breads and artisan breads the ability to hold their shape while baking along with the rich hearty crust prized by bakers. Bagels and noodle dough benefit from the high protein content of these flours giving complex structure and chewy qualities. Generally, you cannot find Clear or high gluten flours at the grocery store. King Arthur will ship it to you or you can visit your local bakery and ask if you can purchase it from them.
There are times when you may want to blend the flours to create just the right amount of starch and protein.