The thing that most Americans want to know when they talk about French flour is: what can they do to approximate French “Type 55″ flour? That’s the kind that’s most commonly used for baguettes and even many pastries (it’s akin to an American all-purpose). That’s an extremely difficult thing to do for reasons I discussed below in the post “What’s the deal with ash content?”. However there several other important differences between American and French flour that make a direct equivalent an all-but-impossible to thing to formulate using commonly available components.
But Joe, flour is just ground-up wheat, how different can the two really be? The answer might surprise you. For one, French flour is milled and mixed to different standards compared to American flour. Typical French bread flours, as I mentioned at the beginning of this long series of posts, are what are known as “straight” flours. A straight flour is what you get when you grind a wheat berry, remove most of the bran and germ and a) don’t sift it into lots of different grades and b) don’t mix it together with other grades from other batches (as American millers usually do). The result is a flour that’s coarser than a normal American bread or all-purpose flour.
The character of the protein (gluten) is also quite different in a French flour, not nearly as elastic as the kind you find in American flour. Though French Type 55 flours routinely list a protein content of around 11.5 percent, they perform more like a medium-protein American flour, around 9.5 percent. That puts them on par, as I mentioned before, with American all-purpose flours. Plenty of bakers try to replicate baguettes or other French breads with high-gluten flours (or mixtures of low and high gluten flours) but the experts are mostly in agreement that too much American gluten is bad for a good French bread.
So when you get right down to it, there’s not much about American and French flours that are the same, other than the fact that they’re all flours. They’re different types of wheat grown in different places, under different conditions, then processed differently and milled differently. The end result is that they behave differently from one another in the same types of applications. Does that mean it’s a hopeless task to try to make a good baguette out of American flour? By no means. Simply select a good, hard all-purpose flour (preferably a Northern one made from a hard red winter wheat) and you’re at as good a starting point as any baker on this continent.