Last week, we looked at different types of white refined flour, but that's not the end of the flour story. While some bags of flour contain nothing but wheat, many are enriched or processed in some way. Have you ever wondered how bleached or bromated flour is different? More importantly, do these processes affect your baking? Here are the answers you've been looking for.
The most common treatment labeling you'll see on the front of a bag of flour is whether it's been bleached or not. Flour in its natural condition isn't pure white, it's more of a cream color. Bread and cakes won't be a bright white if you use unbleached flour. Whether whiteness is important to you or not is up to you. Given the number of other things I throw into a typical loaf of bread, whiteness isn't high on my priority list, though it's more important for cakes, some of which look best when bright white.
How does bleaching work?
Soft, low-protein flours (those used for cakes and muffins) are typically bleached with chlorine gas, and sometimes with peroxide. These bleaching agents aren't supposed to remain in the flour—they are meant to react and dissipate, leaving nothing behind in the flour besides the whiteness.
Soft flour bleaching also affects the protein in the flour, causing it to produce stiffer gluten, which makes it easier to make sturdy cakes using less flour and a higher percentage of sugar. The bleaching process oxidizes the flour, which can produce a tighter surface in biscuit dough, reducing the amount the biscuits spread and resulting in a taller biscuit.
Hard flours (like those used for bread and pizza) are treated differently. What you're likely to see as bleaching agents in hard flours are azodicarbonamide (ADA), potassium bromate, or ascorbic acid. These agents react with the pigment in the flour and also oxidize the flour much like the chlorine used in softer flours. That oxidation improves oven spring and loaf volume.
Have you ever wondered about bromated flour? It's simply a flour that was bleached using potassium bromate rather than another bleaching agent. The use of potassium bromate is banned in several countries. While it is legal in the US, several states require special labeling when it is used.
Bleaching isn't all about color—it's also about oxidation. Oxidation of all flours occurs naturally over time, but bleaching speeds up the process. Without the aid of bleach, the natural oxidation process would take up to six months. Bleaching encourages oxidation, reducing the waiting time to a matter of weeks. While it's an extra step for manufacturers to chemically bleach flour, it decreases the storage time and space necessary at the processing plant. This explains why most bleached flours are cheaper than their unbleached counterparts. Indeed, part of the oxidation process takes place while the flour is in transit from the plant to your kitchen—that's why flour is shipped in breathable paper bags instead of airtight plastic.
Besides bleaching agents, many flours are enriched with iron and B vitamins including thiamin, niacin, riboflavin and folic acid. These are added to the flour to bring these nutrients up to the same level—or higher—than would have been in the original whole wheat flour that included the bran and germ.
Malted barley flour is also sometimes added to bread flours. It has the active enzyme alpha-amylase which helps convert starch to sugar and affects the texture of dough.
A final category of flour with additives is self-rising flour. You probably won't be using it for bread or pizza dough, but it's a convenience product for people who make a lot of biscuits and quick breads. Basically, self-rising flour is an all-purpose flour with salt and baking powder added. To make your own, just add 1 1/2 teaspoons of baking powder and 1/2 teaspoon of salt per cup of flour, and whisk well to combine.
If you make a lot of quick breads and biscuits, self-rising flour might be handy to have on hand. If it's something you only need occasionally, it saves storage space if you make your own as needed. And if you happen to live at high altitude, it's easier to adjust the amount of baking powder in a home mix than it is to add flour to adjust a pre-made self-rising flour.
Whether you're looking for an unbleached, additive-free flour, or you like the benefits of the enrichments and enhancements, it's good to be aware of your options and be able to understand the labels on different bags of flour. As a baking and pizza-making pro, now you'll know when and why there's more than flour in your flour.
About the author: Donna Currie has been cooking for fun and writing for pay since the days when typewritten articles traveled by snail mail. When she combined those talents in a food column for a newspaper in her area, she realized that writing about food is almost as much fun as eating. She launched the blog Cookistry and has now joined the Serious Eats team with a weekly column about baking.