Today, we will discuss gluten present in flours and how it influences their uses. There is a certain consensus on the importance of gluten in the quality of flours, and this is the case in many instances. However, there are certain aspects of gluten that I consider fundamental and often surprise many people when I give lectures or courses. Let’s explore in which processes the gluten network develops and in which ones it does not. In these cases will be easy to produce gluten-free products. We will also look at the type of flour, based on the quality of proteins, needed for each process. I hope you enjoy it.

Gluten

The first thing we need to understand is what gluten is, and it’s not straightforward. The main problem in defining gluten is that, depending on the occasion or the group discussing it, we can refer to different things. Here are the two most common uses of the word gluten:

Gluten for a Celiac

When we talk about the celiac community or gluten-free products, gluten refers to a group of proteins that cause intolerance to this collective. What these proteins have in common are specific sequences of amino acids. Amino acids are the building blocks of proteins, and when there is a specific sequence of amino acids, it seems to be a problem for the celiac community. Besides wheat, other grains like barley or rye also cause problems for celiacs. This intolerance in the celiac community is caused by raw, cooked, or heat-treated proteins. Therefore, we are not talking about a protein with a specific functionality but a protein that causes intolerance in a specific group of people.

Gluten in Baking

In baking, gluten is a protein network that forms when certain proteins hydrate and undergo mechanical work. This protein network is characterized by creating cohesive dough that can be stretched without breaking and has a high capacity to retain gas inside. Therefore, gluten is the protein responsible for the unique properties of wheat flour. These proteins are not found in any other grain, neither barley nor rye, although these grains are not tolerated by celiacs.

As mentioned, gluten is formed when these proteins hydrate and undergo mechanical work, a process that occurs during kneading. The hydration of proteins is a common phenomenon in many recipes, but mechanical work is not. For instance, dough subjected to prolonged kneading, such as bread, puff pastry, pastries, and others, forms the gluten network. However, in very liquid batters, where there is not much friction or significant mechanical action between the whipping paddles and the batter (which is often mixed rather than kneaded), the gluten network does not develop. In some cookie recipes, prolonged kneading is avoided, only mixing the ingredients without providing mechanical work, and in such cases, the gluten network is not formed. In other cases, such as “churros” dough or scalded dough, the protein undergoes heating and it is denatured, losing its functionality. In all these cases (batters, poorly kneaded dough, or scalded dough), the gluten network is not formed or has no functionality. Consequently, the quality of wheat proteins is not important in defining flour quality for these preparations, and it is not very complicated to make gluten-free products (we will discuss this in another post). In contrast, in dough where the gluten network develops, the quality of wheat proteins is usually the main factor defining flour quality for these preparations.

Gluten Quality

Now that we know what gluten is in baking, we should be aware that the proteins forming gluten are gliadins and glutenins, both reserve proteins of the grain. These proteins are concentrated in the endosperm (the inner part of the grain used to make flour). Depending on the quantity of gliadins or glutenins and the types of glutenins, the characteristics of this gluten are different. As mentioned, gluten is a network of proteins, and this network can be very dense and stabilized with strong bonds or more open, with weaker connections. In the first case, we talk about strong flours or dough, and in the second case, we talk about weak flours. Strong flours produce very tenacious dough (difficult to stretch), usually highly elastic (tending to return to their original shape after stretching), and somewhat extensible (the ability to stretch the dough without breaking). Conversely, weak flours create dough that stretches more easily and does not return to its original shape after stretching (or does so to a lesser extent). These weaker doughs can vary in terms of extensibility.

The strength of flours is determined by the wheat variety and growing conditions. Therefore, geneticists, in addition to trying to achieve varieties with high productivity and tolerance to certain diseases, try to ensure these varieties have proteins suitable for subsequent baking use. On the other hand, farmers can improve these varieties’ protein quality through fertilization during grain growth. However, each batch of wheat has different characteristics. Flour companies must analyse, mix, and mill them to obtain a wide range of flours, each suitable for different preparations and with consistent characteristics, so they always perform consistently under the same processing conditions.

What flour do we need for each process?

As mentioned, flours or dough can be more or less tenacious, extensible, elastic, or strong. These properties can be measured with equipment like the alveograph, which we will discuss in another post. While some products require weak, less tenacious, and very extensible flours, others need stronger flours. Let’s provide some general guidelines, but it’s important to note that two bakers may prefer different flours to make very similar bread, because factors like the type of machinery, fermentation conditions, or bakery conditions can influence the dough.

In some products, the gluten network does not form. In these cases, protein quality is not important, but the quantity of these proteins is, as higher protein content means less starch, and the characteristics of both products differ. Generally, low-protein flours are used to prepare these products, as they are more economical and usually better suited for these preparations. However, aspects like particle size or ash content (contamination with bran) should also be considered.

In other products, the gluten network forms, but it should be as weak as possible. This is the case with Maria biscuits, where the dough should not shrink once rolled out (it should be minimally elastic). In such cases, very weak, not very tenacious or elastic, but highly extensible flours are used since the dough needs to be rolled out. Some additives, like sodium metabisulfite, are used in these preparations to weaken the dough.

Conversely, some doughs need to ferment and retain gas formed during fermentation, but ingredients that weaken the dough are added. These ingredients include fats and sugar. Therefore, bakery products with high fat or oil and sugar content require strong flours. Pan bread, which requires a closed crumb structure and clean slices, also needs strong flours, as well as hamburger or hot dog buns.

Slightly less strength (medium-strength flours), good extensibility, and less elasticity are necessary for preparations where dough needs to be laminated, such as puff pastry, croissants, or pizzas. There are important differences in the flours preferred by artisanal producers (usually slightly stronger) and industrial ones. In general, these doughs incorporate some oil or fat to improve extensibility and reduce elasticity but should still retain gas or be rollable without becoming overly sticky, requiring flours with more strength than doughs without these ingredients.

The case of bread is quite complex, depending heavily on the type of bread and the production method. In Spain, low-protein flours are typically used for making common bread (similar to baguette), but doughs are strengthened with additives and enzymes present in improvers. If you prefer not to use additives, it’s advisable to use stronger flours. Breads with conditions that weaken the dough, such as excessive water content or exposure to cold, need stronger flours. Industrial processes typically require slightly softer and more extensible flours compared to artisanal processes. However, each baker should experiment with different flours and choose the one that best suits their process.

In future posts, we will delve deeper into gluten quality and how to measure it. We will also discuss active vital gluten, or gluten that can be used as an improver.

Note

In the animal feed and starch industry, corn protein is often referred to as corn gluten, typically used in feed production. However, this corn gluten is neither “toxic” for celiacs nor capable of creating cohesive dough with gas-retaining properties.

For further information:

Delcour, JA; Joye, IJ; Pareyt, B; Wilderjans, E; Brijs, K; Lagrain, B (2012) Wheat gluten functionality as a quality determinant in cereal-based food products. Annual Review of Food Science and Technology, 3:469-492.