The size of the flour particles affects the texture and volume of the bread. In fact, in Finland, flour is classified by the size of the particle.
Particle Size is Criterion in Finland
In Finland, there are so many different types of flour on the market. Flour is mainly classified by particle size in Finland.
You can tell at a glance from the package what kind of food it is suitable for.
In this section, we will consider more deeply the influence of the particle size of flour.
Particle Size and Flour Properties
As the particle size changes, the properties of the flour also change. The two main changes are described below.
Specific Surface Area
The smaller the particle size, the larger the specific surface area. In other words, even for the same weight of flour, the smaller the particle size, the larger the surface area.
When the surface area increases, there are many changes that occur.
Easier Water Absorption
As the particles of flour become smaller and the surface area increases, when water is added to the flour, the area in contact with the water increases. The more surface area the flour has in contact with water, the easier it is to absorb water (*1).
Easiness to Be Oxidized
As the grains of flour become smaller and the surface area increases, the area of flour exposed to air increases. Flour with added water has the property of reacting with oxygen in the air to make the gluten network stronger. This is because the mercapto group forms a disulfide bond, but I will not go into details. (*1)
In other words, the more surface area the flour has, the more easily it will be oxidized.
The color of flour is affected by ash content and variety, but it is actually related to particle size as well.
As the particle size of the flour becomes smaller and the surface area of the flour increases, the light hitting the surface becomes more diffusely reflected. In other words, the smaller the particle size and the larger the surface area of the flour, the whiter the color will be. This is the same principle as the rock paint used in Traditional Japanese painting.(*5)
There is also a difference in the color of bread and other products. For example, when making steamed bread, flour with smaller particles and a larger surface area will have a whiter color. This is because the smaller particles of flour form a more dense structure. (*1)
Amount of Damaged Starch
Although the amount of protein that affects gluten tends to be the focus of attention in flour, starch accounts for the majority of it.
As the particle size decreases, the amount of damaged starch, the starch whose structure has been destroyed, increases. This damaged starch mainly affects the ease of water absorption. In addition, it also affects how easily starch is broken down, but we will not go into that here.
Ease of Water Absorption
As the amount of damaged starch increases, it absorbs water more easily (*1).
Starch is called a polysaccharide, and is made up of many sugars connected together. When the structure of starch is destroyed, the hydroxyl groups of the sugars are exposed. As the name suggests, hydroxyl groups are easily absorbed by water, which is thought to increase the water absorption rate.
Effect on Cooking
When fine flour is used, the bread becomes denser and has a chewier texture. This is because fine flour tends to form gluten, which makes it harder to puff up.
In Finland, the flour used for pastry is coarser than the flour used for baking. This is because the finer particles form a tighter gluten network, making it harder to puff up and resulting in a denser baked product.
The website of the Finnish wheat brand also says that the coarser particles give a fluffier texture (*4).
Udon and Ramen
As mentioned above, the more damaged starch is, the easier it is to absorb water. If the amount of damaged starch increases too much, the starch will absorb too much water and inhibit the formation of gluten (*3). For example, when making udon noodles, if the flour particles are too fine, the noodles will not be firm enough and will become sticky. It is good to keep in mind that the size of the grain also makes a difference.
Protein Content Also Affects
The above is a discussion of the effect of flour particle size on cooking.