First let’s get a show of hands. How many people here have had someone brow-beat them with the term “ash content”? Come on, don’t be shy. There’s no shame in it. Put’em up. Yep, I thought so. There’s a certain type of bread head out there that simply loves to do that. But let me tell you, there’s nothing about ash content that’s hard to understand. Once you have a general sense for what it means, you’ll be able to go toe-to-toe with even the most heavily-tatted, ringed-and-plugged artisan bread bakers. Just don’t go making fun of the bleak industrial Throbbing Gristle and Mica Levi records they listen to. I won’t be able to help you in that instance.
But what exactly is “ash” and why do you find it in European flour? The answer is that there actually is no “ash” in European flour. Europeans use the term “ash” as a catch-all term for everything in their flour that is not pure wheat starch. Things like bran, germ, protein, minerals and other nutrients. The higher the “ash” content, the more of those kinds of things you find in the flour.
With me so far? The reason it’s called “ash” is because long ago, Europeans developed a method for testing the relative purity of their flour, and they did this by burning it. They found that when you burn flour at a very high temperature, the starch — being made of sugar and therefore very fuel-like — burns away totally, leaving a residue composed of…well, everything else. So when someone tells you that this particular French flour has an ash content of 0.65%, all it means is that when a particular miller burned 10 grams of this flour, they were left with 0.065 grams of ash.
“So what does that have to do with the price of avocado toast in Portland?” you may ask. Well I’ll tell you. Knowing the ash content of a European flour is exactly like knowing the extraction rate of an American or British flour. That one number, by telling you how pure or impure the flour is, tells you by extension how much gluten (protein) the flour has, and how much bran or germ it has. And if you know those things then you have a pretty good idea for how the bread will perform when you bake with it. You even have a sense for what the grind will be.
More on this when I talk about the various kinds of international flours. Meantime, to get a more complete understanding of this subject, I strongly recommend reading the extraction rate post I linked to above. Keep developing those brain muscles, friends — and never let a hipster bread head kick bran in your face again!