Published May 1, 1999. From Cook's Illustrated.
We set out to learn if there was a single all-purpose flour that could best handle most any recipe. Six months later, we had the answer.
All-purpose flour is such a simple kitchen staple. Yet it is a fundamental building block for many home-baked goods. In our efforts here at Cook's to make a poor recipe great or a great recipe even better, we typically take this into account. We test not only amounts of flour, sifted versus unsifted, and bleached versus unbleached; we also try various specialty flours. Often we find that they can make a real difference. For some serious bakers, this is not a problem. They simply stock their pantries with a variety of flours: cake, all-purpose, bread, high gluten, and so on. But for most home cooks this option is neither reasonable nor desirable. We wanted to know if there was a single all-purpose flour that would be best for those who keep only one kind of flour in the pantry.
Before we began testing, we turned to experts in both grain science and baking science to find out what we should be looking for. Most wheat that is milled is made into specialized flours used on a large-scale commercial level. All-purpose is designed to be used in a wide range of recipes written for home cooks who do not have the kind of high-intensity mixers or the expertise necessary to use the specialized flours made for commercial bakeries.
Nevertheless, there are a number of choices a flour company must make when milling all-purpose flour that will influence the way its product performs in recipes. For starters, there is the essence of the flour, the wheat itself. All-purpose flour is typically made from either hard red winter wheat, soft red winter wheat, or a combination of the two. Of the flours we used in the taste tests, five were made from hard winter wheat, one was made of soft wheat, and three were a mix of soft and hard.
Perhaps the primary difference between these types of wheat—and consequently in the flours made from them—is the variation in protein content. Hard winter wheat is about 10 to 13 percent protein, and soft wheat about 8 to 10 percent. Mixtures of the two wheats are somewhere in between. You can actually feel this difference with your fingers; the hard wheat flours tend to have a subtle granular feel, while soft wheat flours feel fine but starchy, much like cornstarch.
High-protein flours are generally recommended for yeasted products and other baked goods that require a lot of structural support. The reason is that the higher the protein level in a flour, the greater the potential for the formation of gluten. The sheets that gluten forms in dough are elastic enough to move with the gas released by yeast but also sturdy enough to prevent that gas from escaping, so the dough doesn't deflate. Lower-protein flours, on the other hand, are recommended for chemically leavened baked goods. This is because baking powder and baking soda are quick leaveners. They lack the endurance of yeast, which can force the naturally resistant gluten sheets to expand; consequently, the gluten can overpower quick leaveners, causing the final baked product to fall flat.
A second important difference in flours is whether they are bleached or not. Technically, all all-purpose flours are bleached. Carotenoid pigments in wheat lend a faint yellowish tint to freshly milled flour. But in a matter of about 12 weeks, these pigments oxidize, undergoing the same chemical process that turns a sliced apple brown. In this case, yellowish flour changes to a whiter hue (though not stark white). Early in this century, as the natural bleaching process came to be understood, scientists identified methods to chemically expedite and intensify it. Typically, all-purpose flours are bleached with either benzoyl peroxide or chlorine gas. The latter not only bleaches the flour but also alters the flour proteins, making them less inclined to form strong gluten. Neither chemical, however, poses any health risks. Today consumers prefer chemically bleached flour over unbleached because they associate the whiter color with higher quality.
Of all the product taste tests Cook's has run, these flour tastings were undoubtedly the most difficult. The differences in flavor between the various versions of the selected recipes were usually extremely subtle. The most obvious differences were often in appearance.
That is not to say, however, that the tests were inconclusive. As difficult as it was for tasters to pick up differences, they were remarkably consistent in their observations. The performance of each of the flours tested, however, was not so consistent.
While the protein guidelines make eminently good sense, to our surprise, the results of our tests did not always correspond. The biscuit test did reveal a certain progression from light, cake-like biscuits produced by the lowest-protein flours to coarser, heavier biscuits produced by the higher-protein flours. But our tasters liked all of the biscuits, except for one that had stale flavors. Another trend we noticed was that lower-protein flours spread more in tests of chocolate chip cookies and muffins. In the pie crust test, however, six of the nine flours revealed no correlation between protein content and texture or flavor.
Further research revealed that proteins are different from one wheat variety to another and therefore from one flour to another. The quality can vary considerably. Because flour is not a high-profit commodity, manufacturers often mill from strains of wheat that offer the greatest yield of flour from a given amount of grain, a practice that can be at cross-purposes with good baking properties.
As an overall category, though, the four bleached flours in our tests in fact did not perform as well as the unbleached flours and were regularly criticized for tasting flat or carrying "off" flavors, often described as metallic. These characteristics, however, were more difficult to detect in recipes that contained a high proportion of ingredients other than flour. Coincidentally, our cake tests and chocolate chip cookie tests (both sugary recipes) were the two tests in which off flavors carried by the bleached flour went undetected or were considered faint.
Despite the variations and subtleties, however, the good news is that we did end up with two flours we can recommend wholeheartedly. These two flours regularly baked up highly recommended baked goods, producing a more consistent range of preferred products than the other seven flours in the taste tests. There is an old bakers' saying that "all-purpose flour is good for everything but not real good for anything." After months of tests, we would have to differ. It can be awful at some things and really good at others. It depends on which flour and which recipe. If you are going to have only one flour in the house, though, our advice is to choose one of these two.