White flour is white flour – but not all white flour is created equal. Differences in milling, as well as how the flour is handled after it has been milled, can have major effects on the flour. And one of the main ways of treating flour is through bleaching. Refined wheat flour (ie not whole wheat), such as all purpose flour, cake flourAND self rising flour, are either bleached or unbleached during production. But what exactly does this mean?
Briefly: Unbleached flour is aged naturally after milling, during which time it slowly oxidizes and turns white. Bleached flour, on the other hand, uses chemical treatments to manually speed up this process. Both can be used interchangeably in baking; so why should you choose one over the other?
Let's break it down a little more.
Photography by Rick Holbrook; food styling by Kaitlin Wayne
Understanding the difference between bleached and unbleached flour
During the 1940s (the heyday of Wonder Bread, the first commercially available sliced bread), white flour became a popular tool in commercial bread. And while Wonder Bread is no longer the only, nor the most popular, bread on the market, modern millers are still primarily in the business of making white flour. The first step in achieving this is to separate the bran and germ of the wheat grains through the milling process itself. This is what distinguishes whole wheat flour, which is made from the entire kernel of the wheat, from white flour, which is just the ground endosperm.
The next step in this process is to “bleach” the remaining flour. Given time and exposure to air, the flour will slowly oxidize and turn white on its own. This rest period, about two weeks in the summer and up to a month in the winter, also changes the chemical composition of the flour in order to create a more elastic dough. This is unbleached flour, and it's how King Arthur Baking Company makes all of our refined flours.
But instead of using time as an agent, as we do, many millers use chemicals to bleach the flour almost instantly. As the flour leaves the line to the mill, bleaching and oxidizing chemicals are added to speed up or completely replace the aging process. This is how bleached flour it is done.
Anne Mientka
Wait, what exactly does “bleached” mean?
Chemicals used to bleach and/or oxidize flour include chlorine dioxide, benzoyl peroxide, and chlorine gas, which are all allowable additives (although King Arthur Baking Company flours contain none of these). Benzoyl peroxide leaves behind some benzoic acid; Some people with a keen sense of taste recognize benzoyl peroxide in baked goods because it has a bitter aftertaste, but its addition does not significantly change the baking qualities.
Chlorine gas reacts with the flour to change its absorption, flavor, pH and, in the case of some cake flours, its performance. In baked goods where other ingredients do not mask it, it gives a distinct flavor to people with sensitive palates.
The most controversial additive used today is potassium bromate, which is still used as an oxidizer and “improver,” strengthening the dough and allowing for greater oven acceptance and higher oven rise. However, it has come under scrutiny, as tests with it have shown it to be carcinogenic in animals and possibly humans. Since 1991, flour sold in California containing potassium bromate must carry a warning label, and it was recently banned in the state as well. It is also banned in Canada, Europe and Japan, and is likely to be banned in other parts of the United States one day. (This is why King Arthur bags advertise that our flour is “Never Bromatized.”)
Choosing the right flour
Ultimately, the flour you choose to bake with is entirely up to you. Bleached and unbleached flour can be used interchangeably in any recipe without much apparent difference. But understanding what sets them apart can help you make your decision.
And if that decision is to bake with unbleached flour? You know we got you covered.
