The three major distinctions that matter to most bakers are the color, season, and hardness of the wheat.
Red vs. White: This refers to the color of the bran, which is the outer protective coating of the wheat kernel. Bran color is less important in refined flours than in whole wheat flours.
Winter vs. Spring: While it probably doesn’t matter to you when your wheat was planted or harvested, it’s useful to know that flour from winter wheat has an average protein content of 10-12 percent and medium gluten strength, while flour from spring wheat has an average gluten content of 12-14 percent, and high gluten strength.
Hard vs. Soft: This is the most important category. Flour from hard wheat has a higher protein content and stronger gluten-forming proteins, making it better for yeasted products. Flour from soft wheat has less protein, low gluten strength, and is are better for chemically-leavened products like cakes, muffins, biscuits, and cookies.
Any flour can be any combination of those three categories, so you could have a hard red spring wheat or a soft white winter wheat, for example.
On thing to keep in mind is that protein and gluten are related, but not exactly the same. The proteins in the flour create gluten, but a high-protein flour may not always create the best quality gluten. So the strength of the gluten is as important as how much protein there is to start with. However, the more protein there is in a flour, the more potential gluten there is as well.
Flour quality isn’t just about the grains themselves. Milling plays an important role. When grain is milled, the first product is straight flour, which contains some bran and germ. Bakers in France might use straight flour, but it’s uncommon in the US where straight flour is sifted into other categories that you’re more likely to see on store shelves.
Clear Flour is what’s left over after the patent flours have been removed from straight flour. It is darker than the patent flours and has a higher ash content. The only clear flour I’ve seen marketed is first clear. It’s made from hard wheat and blended with lower-gluten flours. First clear is good for whole wheat and rye flours, where the darker color isn’t a problem. Because higher mineral content in first clear flour, many people like to use it to feed sourdough starters.
Speaking of ash content, that doesn’t mean there’s burned crud in the flour. It’s really all about the amount of mineral content in the flour. Basically, when a flour sample is burned in a lab, the ash that is left is the minerals in the flour.
European flours are more likely to be categorized by ash content, while American flours are more concerned with protein content. In theory, as ash goes down, protein goes up, but it also depends on the protein level that was present to begin with.
Italian flours are classified by the fineness of the grains and the amount of bran and germ removed. Type 00 flour is the finest grind, is very powdery, and has the least bran and germ remaining. Following Type 00 are Types 0, 1 and 2 with Type 2 being the coarsest flour. Since this is all about milling and not about protein, it’s possible for 00 flour to have varying amounts of protein depending on the original amount in the grain. However, since the Type 00 flours have less bran and germ, they would have a higher percentage of protein than a Type 1 flour milled from that same grain.
Many bakers choose to substitute lower-gluten American flours for the relatively higher-gluten Type 00 flour used in Italy for pizza. For one thing, the gluten quality in those Italian flours is not equivalent to the gluten in American hard red wheat that’s typically found in bread flour. The gluten in American bread flours is hard and springy and results in a very elastic dough, whereas the Italian gluten is firm but not as elastic, making it better for stretching or rolling pizza and pasta.
One thing to keep in mind is that the Italian flours have less gluten overall, with an average range of about 7.5 to 11 percent, and generally not much higher than 9.5 percent. Lower-protein Italian flours are often labeled as grano tenero, while the higher protein flours would be grano duro.
The “Italian-Style” flour made with American wheat sold by King Arthur Flour has a protein content of 8.5 percent, putting it in the same range as Italian flours. Other types of American flour vary in protein content by manufacturer, but in general, cake flour has 6-8 percent protein, pastry flour has 8-10 percent, all purpose flour has 10-12 protein, white whole wheat flour has about 13 percent, bread flour has 12-14 protein, and first clear flour has about 15 percent.
Unfortunately for American bakers, flour labels aren’t always very forthcoming about what sort of wheat is in the bag or exactly how much protein or ash it contains. However, much of that information can be found at product websites or by emailing the companies.
While bread and pizza-makers concern themselves with the amount and quality of gluten in flour because of the structure it provides, that protein also has another effect on dough – higher-protein flours absorb more water. What that means to the baker is that a 67-percent hydration dough might feel wetter or drier depending on the brand and type of flour being used.
For commercial bakeries or die-hard bakers who use the same suppliers consistently, the inconsistencies among manufacturers aren’t an issue. But for casual home bakers, it’s just one more reason why the same recipe might have different results on different hands or on different days.