Ash Content in Flour: What It Is and Why It Matters for Baking

Ash content in flour is a key technical specification primarily used for flour classification. In this article, we’ll explore what ash content is, what it indicates, why it matters, and how it affects both the dough and the final product

What Is Ash in Flour

The wheat kernel consists of three parts: the endosperm, bran, and germ. The endosperm, which contains all the gluten-forming proteins, makes up the majority of the wheat kernel. What we refer to as “white flour” is essentially just the endosperm, separated from the bran and germ.

On the other hand, wholemeal flour is made from the entire wheat kernel and includes both the bran and germ. The more bran a flour contains, the closer it is to being considered “whole wheat”.

The ash content is the tool used to measure the amount of bran that remains in the flour. Typically, the ash content in flour ranges from 0.35% to 2%.

What Does the Ash Content in Flour Indicate

The ash content in flour is technically an indicator of its mineral content. To determine the ash content, a sample of flour is burned at a high temperature. Only the minerals ‘survive’ this process, so the resulting “ash” represents the mineral content of the flour sample.

The ash obtained after burning is then weighed in relation to the weight of the original flour sample, which gives the ash content of the flour. For example, if the original flour sample weighed 100 grams and the resulting ash weighed 0.5 grams, the ash content of the flour would be 0.5% (0.005 = 100 / 0.5).

Most of the minerals in flour are found in the bran; Therefore, the ash content provides insight into the amount of bran remaining in the flour after milling, or in other words, how “pure” the flour is and how effectively the bran has been separated from the endosperm.

The lower the ash content, the more “refined” the flour is, indicating that it contains less bran (and also contains fewer nutrients, as the bran and germ hold most of the wheat kernel’s nutrients).

To conclude: Higher ash content = Higher mineral content = Flour that contains more bran (and usually germ as well).

Flour with a higher ash content will be darker (see photo above), which will result in a darker color for the baked product. A higher ash content can also affect the texture, flavor, and nutritional values of the baked product due to the increased presence of bran (and sometimes germ).

Additionally, the water absorption capacity of flour increases with higher ash content, due to the higher presence of bran.

In the past, the ash content in flour was used as an indicator of its quality (a lower bran content was considered a sign of higher quality, as it suggested better separation between the endosperm and bran).

However, as bakers today, the ash content is not significant to us and is merely a technical measurement that primarily concerns flour mills for quality control and regulatory compliance purposes.

Classification of Flour Based on Ash Content

All European flours are primarily classified based on their ash content. Below is the classification of Italian, French, German, and American flours. For additional European flour standards, refer to this presentation.

It is important to note that the classification of flours above is based solely on their ash content. Aside from meeting the specified ash content range, these flours can possess a wide range of characteristics.

For instance, Italian “00” flours can vary in protein content (and other characteristics), ranging from 9% to 14%; The only information conveyed by “00” flour is simply that it contains an ash content of 0.55% or less.

The same applies to all other types of European flours, be it German, French, or Italian (for specific classification of other European countries, refer to the presentation linked above).

Impact of Ash Content on Fermentation

The mineral content indicated by ash levels also influences fermentation activity.

Generally, higher ash flours provide more minerals that act as nutrients for yeast and bacteria during fermentation. These minerals, particularly magnesium and iron, help activate enzymes essential for yeast and lactic acid bacteria metabolism, potentially leading to more vigorous fermentation.

However, this effect is relatively minor compared to other factors affecting the rate of fermentation.

Impact of Ash Content on Gluten Development and Crumb Structure

Higher ash content flour contains more bran particles that interfere with gluten development.

These bran particles act like tiny blades, physically cutting through developing gluten strands. This leads to a tighter, less open crumb structure in the final product. The higher the ash content, the more significant the impact on crumb structure.

For pizza making, lower ash content flours (like 00) are often preferred because they support optimal gluten development with minimal interference from bran.