For a single ingredient, wheat flour has an amazing number of iterations. It can be gruel or wedding cake, Wonder bread or baguette, croissant or hot dog bun. Flour seems simple, but it can give the occasional baker some anxiety — what exactly separates a good pie crust from a bad pie crust when it’s just flour, fat and water? Why is this cookie recipe calling for bread flour, and should I care that I don’t have it?
Read on for a primer. A little de-mystifying means better sweets for you.
The thing that separates one type of flour from the next is its gluten protein content. The difference is big enough that a recipe that calls for one type of flour often turns out very differently if another type of flour is used. For one, high protein flours absorb substantially more water than low protein flours, and will produce stiffer doughs with the same proportion of water. Baking is all about proportions, and a recipe that calls for bread flour takes this into account in the recipe’s ingredient list.
As a guideline, different types of flour are classified under the type of baking they are normally used for. The flour that’s high in strong gluten proteins is generally called bread flour because it makes the highest, chewiest, lightest bread loaves. The gluten forms strong, straight bonds that make a stretchy-er product, a trait that works for other baked goods too, from sticky buns to that amazing New York Times chocolate chip cookie.
If a bread recipe specifically calls for bread flour, be sure to use it. The rising, and most certainly the kneading, needs to happen to the gluten proteins in bread flour. If you’re not using it, you’re setting yourself up for disappointment.
Christina Tosi of Momofuku Milk Bar fame uses bread flour for her cookies, and in her book calls it “one of those secrets.” The extra large pile of butter in her cookies makes a difference, and she cautions about over-mixing when using bread flour — too much mixing could stiffen and toughen the end product. This is a danger for most cakes and cookies. The trick is to stir in the flour by hand and stop stirring the instant you can’t see flour any more.
Pastry flour has a low gluten protein content, and cake flour even lower. This low protein content makes for a more tender baked good. Think of a tall layer cake. Do you want it to be stiff and chewy? No, you do not. You want it to be tender, with a round crumb. That’s why you use this flour when you’re told.
All-purpose flour has a protein content that sits between pastry and bread, and is the most commonly used flour. (Though I’ve found that recipes that play around with this standard can produce some pretty great textures.)
FAKE FLOURS There are a few tricks to use one flour to mimic the gluten content of another. The operative word here is “mimic” — you can’t really turn an all-purpose flour into a pastry flour, but you can try to fool the gluten proteins into acting differently.
To approximate pastry flour with all-purpose, use one part (by weight, preferably) of cornstarch (which has no gluten) to two parts all-purpose flour.
To fake all-purpose flour with pastry flour, add ¼ part vital wheat gluten to 2 parts pastry flour. How you find yourself in a situation with pastry flour and vital gluten, but no regular flour, I don’t know, but there’s the solution just in case.
Cake flour can’t be mimicked — its starch and fats have been altered by chlorine to be able to take drastically different proportions of sugar and liquid for a very distinctive, velvety soft texture. For the most delicate cakes, like a lemon chiffon, you will have to drag yourself to the store and get a box of cake flour. For less fussy cookies that call for cake flour, you can get away with whipping up a batch of fake pastry flour.
AND YET MORE FLOURS Whole wheat flour has the highest protein content of all, but a lot of the protein comes from the germ and aleurone layer of the wheatberry, which doesn’t form gluten, and the germ and bran particles get in the way of gluten formation. Substituting wheat flour in a recipe that calls for a white flour will throw off the moisture proportions of the recipe and significantly alter the texture. Best to find an equivalent recipe written specifically for whole wheat flour.
Graham flour is an 1800s version of a healthy whole wheat flour, and is usually white flour with the germ and bran added back in. It tastes different from whole wheat flour, but one can be substituted for the other.
Durum wheat flour — the kind used for pasta — is an entirely distinct species of wheat and shouldn’t be substituted.
SEEDS OF GRASS Staying true to the type of flour is the difference between a good cookie and an amazing one, an ok cake or a great one. In the end, it’s not that big a deal, deciding on a flour is more of an assessment on your tolerance for imperfection at that moment.
What’s certain is that flour is more complicated that it looks.
Flour’s been around for 10,000 years, and was one of — if not the first — plant to ever be cultivated by humans. So the history of flour — and the things we can make with it — is closely tied up with human technology. The part that we use for white flour is are the insides of tiny, individual seeds of grass. It used to take the most muscular men hours to grind wheatberries into an edible meal, and even then, it could only be made into a starvation-delaying, gloppy mush.
A few hundred years ago, separating the germ from the bran and endosperm advanced from being powered by humans or animals, to getting milled with the power of flowing water. The flour this yielded made a lot more than mush, but a cookbook from 1747 still instructs you to beat a cake batter “all well together for an hour with your hand, or a great wooden spoon.”
These days, electric mills slice open wheatberry seeds and a highly sensitive machine separates each particle of ground up endosperm by its miniscule weight, to give us white flour. This sounds like the last word in milling technology, but to this day we can only remove about 75% of the endosperm, but it makes up 83% of the seed. More exact milling could mean higher grade flours for ever-better textures.
That’s just milling techniques – to this day research scientists still dedicate themselves to wheat science and we can only hope that one day, all that mental exertion will translate to a baked good of unimaginable deliciousness.
FURTHER READING On gluten-free: “It’s rather interesting that the whole celiac disease problem has created a celiac fad diet,” says Dr. Leo Treyzon, who specializes in gastrointestinal disorders at the UCLA. And, “I think there’s a perception that gluten-free equals health. It’s just not the case.” Both from NPR.
Measuring flour correctly makes all the difference. If you don’t have a baking scale, here’s how to do it: How to measure flour, Food52 (video)
Remember the global food and grain crisis? Bankers figured out that bread is pretty important to people, then found a way to mess it up. “How Goldman Sachs Created the Food Crisis,” Foreign Policy.