Flour Protein Content Affects Gluten Formation and Texture

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In Japan, wheat flour is classified as light flour or strong flour based on the amount of protein in the flour. Here is a summary of the properties of each and their suitability for cooking.

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Reasons for Different Protein Content

The most significant factor in determining the protein content is the variety of flour. Some are higher in protein and some are lower, and each is grown to suit the local culture, climate and soil.

Protein content also varies with ash value. This is due to the fact that the center of flour with low ash content has low protein content, while the outside has high protein content.

Protein Content and Flour Classification

In Japan, strong flour and light flour are determined by the amount of protein in the flour (*1).

Protein content(%)Classification
11.5-12.5Strong flour
9-11.5Semi-strong flour
8-9Midium flour, Plain flour
6.5-8Light flour

Protein Content and Flour Properties

As the amount of protein changes, the properties of the flour also change. The two main changes are described below.

Water Absorption

As the amount of protein in flour increases, the water absorption rate increases (*2).

Protein is a substance made up of a number of amino acids. Amino acids have hydrophilic parts called amino groups, carboxy groups, and hydroxyl groups. Therefore, as the amount of protein increases, the water absorption rate is also expected to increase.

Gluten Formation

As the protein content of flour increases, gluten is more likely to form.

Flour contains more than 80 different proteins (*1).Of particular note are gliadin and glutenin. Gliadin and glutenin together make up about 80% of the protein in flour. These two proteins also produce gluten, the most important characteristic of wheat flour.

As the amount of protein in flour increases, the amount of gliadin and glutenin increases, which in turn increases the amount of gluten formed from gliadin and glutenin. Thus, when the protein content of flour increases, gluten formation becomes easier.

Protein Content and Effect on Cooking

The higher the protein content, the higher the water absorption rate and also the amount of gluten formed. Here are some foods that are particularly affected. For other foods and effects other than protein content, see here.
Flour's Protein Content and Particle Size Affect Cooking
Flour has different properties depending on the protein content and the particle size. Let's check it out how they affect the cooking.

Tempura

Tempura is known for its crispy texture. Tempura recipes always come with a warning to use light flour and not to over mix. The purpose of using light flour is to prevent moisture retention, and not mixing it in prevents the formation of gluten.

Udon and Ramen

Plain flour is often used for udon, and semi-strength flour for ramen.

If you use light flour, not much gluten will be formed and the noodles will lack firmness. On the other hand, if you use strong flour, gluten will form quickly and the dough will become hard, making it impossible to knead, resulting in noodles with less firmness. If you use plain flour, it is easier to knead and you can make noodles with a firm texture.

Bread and Cakes

In bread and cakes, where the gluten is allowed to form and then puff up, there are two main effects.

The first is the texture. Light flours with low protein content will have a fluffy texture, while strong flours with high protein content will have a chewy texture.

The second is volume. The higher the protein content, the stronger the gluten network is formed. Therefore, the higher the protein content, the less likely it is to puff up when yeast or baking powder is used. In other words, the lower the protein content, such as light flour, the larger the volume, and the higher the protein content, such as strong flour, the smaller the volume. (*3)

I would like to reiterate that protein content is not the only criterion for evaluating the protein in flour. Flour contains more than 80 different proteins (*1). The detailed percentages vary depending on the type of wheat, such as soft or hard wheat, and the region of origin of the wheat. Of course, the nature of the gluten produced is also affected by this.

However, the fact remains that gliadin and glutenin make up the majority of the protein content. And it is still a parameter that can be easily adjusted in our daily lives.

Particle Size Also Affects

This is a discussion of the impact of the protein content of flour on cooking.

In Japan, flour is mainly categorized as light flour or strong flour, but there is actually another parameter that affects cooking besides protein content. It is the particle size of the flour. For more information, please click here.
Flour Particle Size Affects Bread Texture and Volume
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.

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