You have likely already noticed this while shopping or leafing through a cookbook: on bags of flour, enigmatic codes such as T55, T65 or T150 are proudly displayed. Behind these names that we encounter everywhere lies a precise and essential scientific indicator for cooks and bakers: the ash content..
This term refers to the quantity of mineral substances (ash) remaining after the complete combustion of a flour sample at a high temperature (generally around 550°C to 900°C). Contrary to what the name suggests, this "ash" does not result from contamination but represents the minerals naturally present in the wheat grain (calcium, potassium, magnesium, iron, etc.).
Origin of minerals: The secret of the shell
To understand the utility of this rate, one must look at the structure of a wheat kernel, which consists of three main parts:
- The kernel (or albumen): It is the heart of the grain, rich in starch and protein (gluten). It is very low in minerals.
- The wheat germ : The living part of the grain, rich in nutrients and healthy fats.
- The envelope (or bran): The outer layer that protects the grain. It is this layer that concentrates the vast majority of the minerals and fiber.
The more refined (white) the flour, the more we eliminate the husk and the germ to keep only the kernel. Therefore, The less whole-grain a flour is, the lower its ash content..
The official classification of flours (in France)
The ash content is expressed in milligrams of minerals per 100 grams of dry matter It serves as the basis for the official classification of bread-making flours:
- T45 : Very white flour, low in minerals (less than 0.50 g of ash). Ideal for the fine pastry, brioches and creams.
- T55 : Classic white flour (between 0.50 g and 0.60 g). This is the ultimate all-purpose flour, used for the standard white bread and pizza.
- T65 : Traditional French flour (between 0.62 g and 0.75 g). It contains slightly more bran, ideal for the traditional-style bread and the crusty French baguettes.
- T80 and T110 : Light brown or semi-wholemeal flours (between 0.75 g and 1.20 g). They provide more flavor, fiber, and minerals.
- T150 whole wheat flour (more than 1.40 g). It uses the whole grain, offering a maximum ash content, abundant fiber, and a very rich nutritional profile.
Why is the ash content important?
The ash content directly influences the organoleptic and technical properties of the flour:
- Nutritional value: 150 A high-extraction flour (such as T150) is much richer in fiber, B vitamins, and minerals than white flour (T45 or T55).
- Baking performance: Minerals and bran fragments alter water absorption and the structure of the gluten network. The higher the ash content, the more water the dough requires and the less it rises, resulting in bread that is denser but more rustic and flavorful.
- The colour : It determines the colour of the crumb, ranging from pure white (T45) to a gray or brownish-gray shade (T150).
