Saturday, December 4, 2010
Without looking at the tiny type in the ingredients list, one common treatment you’ll see listed prominently on the front of the bag is bleaching. Or it will just as prominently proclaim that it’s unbleached.
Flour in its natural condition isn’t pure white, it’s more of a cream color. The resulting bread – or cake, if that’s what you’re making – 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.
However, a bright white color might be more desirable in cake flour, since some cakes are intended to be pure white, and even colored cakes might look better without the yellow hue of unbleached flour.
But bleaching isn’t all about color – it’s also about aging. Flour is bleached not only to make it brighter, but also to oxidize the surface of the grains. That oxidation occurs naturally over time, but bleaching speeds up the process.
Soft 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.
That bleaching process also stiffens the gluten, which makes it easier to make sturdy cakes using less flour and a higher percentage of sugar. In biscuits, the oxidation produces a tighter surface on the biscuit dough, which reduces the amount the biscuits spread and results in a taller biscuit.
Different bleaching agents are used for hard flours. They 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. What you’re likely to see as bleaching agents in hard flours are azodicarbonamide (ADA), potassium bromate, and ascorbic acid.
If flour wasn’t chemically bleached, it would naturally oxidize as it aged, but the flour wouldn’t be as white. Also, chemical bleaching speeds the aging process from as long as 6 months for natural aging, to just a few weeks with a chemical process. While it’s an extra step for manufacturers to chemically bleach flour, it also decreases the storage time (and space) necessary at the processing plant. This explains why most bleached flours are cheaper than their unbleached counterparts.
Back in the old days, people aged their own flours by leaving them in cloth sacks where the oxygen could get to the grains and naturally age them. Now, unless you’re buying freshly-milled flour from a farmer or small mill, the flour you buy has been aged for you – either chemically or by time.
One experienced baker told me that flour should be used extremely fresh – less than a day after milling – or after long aging. But flour that is in between those extremes is difficult to work with and produces inferior product. I can’t confirm that, but I do know of one bakery that uses flour that is milled just prior to baking, right on the premises, so there seems to be some truth in that theory.
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 that helps convert starch to sugar and affects the texture of dough. There are other sources for this enzyme, but they must not be as common as the malted barley, based on the flour bags I’ve read.
The last flour category that has additives is self-rising flour. You probably won’t be using it for bread, 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 up to you. There are plenty of options available on the store shelves. At least now when you read the labels you’ll know why there’s more than flour in your flour.
Technique: Flour Additives and Enhancements
Serious Eats|Techniques and Tips|