Quality of cake flours

Quality of cake flours

Just as with cookies, there are different types of cakes, and they don’t all have the same requirements in terms of the quality of the flours used. In the Anglo-Saxon world, the names of different cakes are very clear, and we can distinguish pound cakes, layer cakes, chiffon cakes, sponge cakes, angel cakes, etc. But in the Spanish-speaking world, these designations are not as specific, and we rely more on formulations to understand what we’re talking about. Even within different Spanish-speaking countries, the names are not the same. Fortunately, we can divide cake types into two categories: those in which an emulsion is formed, with the presence of fats or oils that facilitate air incorporation, and those in which air incorporation is more based on the foaming action of egg whites. The former category includes typical homemade breakfast cakes or Spanish muffins, or cupcakes. These cakes are much juicier, precisely due to the presence of fats and oils. In the latter case, we have cakes called “sponge” cakes, which are drier and are usually used for making pastries, filling them with juicier substances like jams, creams, whipped cream, chocolate, etc.

General standards for all cakes

We have talked several times about aspects that should always be considered for any flour application. Aspects such as moisture content and ash content are always important. The moisture content is usually around 14-14.5%, at least in Spain, but it’s important that it’s consistent to avoid differences in formulation (drier flour would require more water addition). As for ash levels, they should be low, as higher ash content indicates that the outer layers of the grain have been removed to a greater extent.

In addition to moisture and ash, it’s important that flours do not have elevated enzymatic activity, either due to grain germination in the field or the attack of certain insects, like “garrapatillo”.

As a general rule, gluten formation doesn’t occur during the cake-making process because the mixing blades do not encounter the necessary resistance to provide mechanical work due to the more liquid or fluid nature of these batters. Diluting the flour and its proteins by mixing them with other ingredients like sugars, fats or oils, and eggs also does not promote gluten formation. In some cases, such as certain muffin batters, which are less liquid, gluten formation may occur, albeit partially, but these are exceptions. Therefore, if gluten formation does not occur, the characteristics of the flour’s proteins, and analyses like alveograph, farinograph, extensograph, and similar tests based on the quality of the protein network, do not provide much useful information for making these types of products.

Fat-based cakes

These cakes are characterized by starting with a batter in which air is incorporated in the form of small bubbles. If you observe it under a microscope, you will see that these bubbles are surrounded by a dark layer formed by fat or oil, which plays an important role in stabilizing them. In these batters, it’s important for the bubbles to remain separated and not move excessively. It’s not the time to explain it in detail now, but in these types of emulsions, bubbles will have greater mobility the larger their diameter and the lower the viscosity of the surrounding medium. If a bubble has too much mobility, it can combine with a neighboring bubble, forming larger bubbles with even greater mobility, and the system becomes unstable, causing the bubbles to escape.

Flour contributes to increasing the viscosity of the medium surrounding these bubbles, reducing their mobility. Therefore, as we explained in the entry on flour quality for cookies, the water absorption capacity of flours, which determines their thickening power, is important. This capacity should be consistent. It’s not good if it’s too low, as it would increase the mobility of the bubbles, but it should not be too high either, as it would reduce the batter’s expansion capacity. This water absorption power can be measured, as we explained before. However, we also know that it depends on the flour’s components. For example, protein has a higher water-holding capacity than starch, and damaged starch has a higher capacity than undamaged starch. The arabinoxylans present in flour are the components with the highest water absorption capacity. It’s also important to note that it’s not necessary for flours to have a high water absorption capacity; it just needs to be consistent. Formulations are adapted to a certain water absorption capacity of flours, and it’s also desirable that this is achieved with a similar composition. Therefore, for flours intended for making this type of cake, it’s important to establish a flour moisture level, ash content, as we already mentioned, and also a specific protein content. In this case, the protein content is more important than the quality of these proteins. The content of damaged starch and arabinoxylans, is more difficult to measure, but the water absorption capacity can be measured, as we discussed in the case of flour quality for cookies.

Some of you may have heard that the particle size of flours is also important, and while this is true, it’s much more important for foam-type cakes than for those based on fats or oils. Under normal conditions, the particle size of wheat flour should not be problematic, as wheat is a relatively soft cereal that tends to produce fine flours. However, in some cases, millers may try to use slightly harder varieties to produce these types of flours, resulting in a coarser final flour that can cause problems in making certain cakes. Particle size is a more significant issue in gluten-free flours, as we will discuss later.

What happens during baking is also important. On the one hand, the starch in the batter gelatinizes due to the presence of water and the increase in temperature. The temperature at which this gelatinization occurs is important because before it happens, the batter cannot retain the gas produced, and once it’s complete, the consistency of the batter has increased to the point where it can no longer expand. The greatest increase in the batter occurs while the starch is gelatinizing. Fortunately, the gelatinization temperature of wheat starch is quite consistent. While the presence of sugars or other substances can affect this temperature, the formulations and leavening agents are manipulated to coordinate gas production and achieve different shapes, with a more or less pronounced rise in the central part of the final product. Thus, the gelatinization temperature of wheat starch is around 60°C (140°F), but in these systems with high sugar content, and made with flour instead of starch, it usually gelatinizes at temperatures close to 90°C (194°F). However, this doesn’t depend on the protein, at least in principle. What is important is that the starch content of the flours is consistent, and this is usually controlled through protein content (easier to measure), as higher protein levels lead to lower starch content. It’s also important that the starch is not excessively degraded because, in this case, it may not gelatinize, or the consistency achieved after gelatinization may not be the same. However, this is not usually a problem in normal flours.

However, there are times when cakes collapse or fall during the final stages of baking or at the beginning of cooling. While gelatinized starch tends to increase in consistency during cooling due to retrogradation phenomena, which can affect the texture of cakes, this change occurs after the cakes collapse. It’s known that the structure that supports the volume of cakes during these final stages is formed by the coagulation of egg protein, primarily from egg whites. But it seems that wheat proteins also have the ability to coagulate and interact with egg proteins. Therefore, a certain percentage of protein in wheat flour is desirable. It’s also important that this percentage is consistent.

In general, flours used for making this type of cake are usually low-protein flours from soft wheat, which do not tend to have a very coarse particle size or a high content of damaged starch. However, it’s necessary to control their moisture content, ash content, and protein content, the absence of enzymatic degradation, and, if possible, their water absorption capacity.

Foam Cakes

Foam cakes differ from the previous ones in that they incorporate much more air into the batter. This is achieved either by beating the egg whites separately (or with sugar) and then mixing this batter with the rest of the ingredients, being careful not to break the structure of the foam formed, or by incorporating some type of emulsifier. If you look at the final batter, you will see that the number of bubbles is much greater than in the case of batters made with fat or oil, and the size of the bubbles is much smaller. In some cases, there is no need to include leavening agents in the formulations (in fact, it could be detrimental), and the increase in volume simply occurs due to the expansion of the bubbles present. It’s known that gases expand with heat. In this type of structure, flour, like in oil-based cakes, acts as a thickening agent, increasing the viscosity of the paste between the bubbles, reducing their mobility, and providing stability to the system. Just like in the previous case, the same parameters related to water absorption capacity should be controlled.

The first difference in flour quality requirements between these cakes and the previous ones is particle size. The reason is not entirely clear, but these cakes are very sensitive to the particle size of flours, with smaller particles being preferred. Two explanations are given for this need. First, it’s possible that starch particles are located at the interface between the bubbles and the surrounding substance, protecting them from possible coalescence phenomena. This is what is referred to as “Pickering” emulsion. This wouldn’t be the only system helping to stabilize the emulsion, as egg proteins also assist in this process, but multiple systems work together. Thus, small particles, especially those from soft wheat, break more easily during mixing, releasing starch granules that facilitate this task. In fact, some formulations recommend incorporating a small percentage of starch. The other explanation is that large particles can break the structure surrounding the bubbles, reducing their stability. Generally, flours from soft wheat have a fine enough particle size. If the wheat is not very soft, the coarser milling streams, which different millers are usually aware of depending on their milling scheme, can be removed. Flours can be micronized, which can be beneficial if done correctly. However, caution must be exercised during this process, as overly aggressive micronize can generate a higher percentage of damaged starch, which could be detrimental by increasing the thickening power and altering the gelatinization process.

The second difference from the previous case lies in the importance of proteins in stabilizing the cake after baking. In these cases, it seems that egg proteins are sufficient to stabilize the cake, provided that the bubbles within the batter are stable (maintaining a small diameter). In fact, it’s possible to make this type of cake with a certain percentage of starch in the formulation, and thus with a lower protein content. However, this issue is not yet fully studied. Moreover, maintaining a consistent protein content is necessary due to its effect on water absorption capacity.

Gluten-free cakes

When making gluten-free cakes, the same precautions as with wheat-based cakes must be taken. Therefore, a key factor will be the water absorption capacity of the flours or flour/starch blends. However, the variability in gluten-free flours, depending on the source of cereals, particle size of the flours, and the milling system, is much greater than in wheat flour. Therefore, controlling this aspect is even more important.

However, perhaps the most important factor in gluten-free flour for making cakes is particle size. In general, the grains from which these flours are made are much harder than wheat, and after normal milling, the particle size is much larger than that of wheat flour. These particle sizes will particularly affect the quality of foam cakes, but they can also affect those based on oil. These flours can be forced during milling to reduce their particle size, but great care must be taken not to excessively increase the damaged starch content, as this would affect the water absorption capacity of the flour. In other words, obtaining fine flour by separating the finest particles obtained in conventional milling is not the same as obtaining it by re-milling coarser particles obtained. In the first case, the particles are usually from the softer parts of the grains, with low damaged starch content, while in the second case, the particles come from the harder parts of the grains, and the damaged starch content will increase, along with the energy costs.

The gelatinization temperature of the starches present in these flours is also not the same as that of wheat, but the presence of high sugar amounts makes them quite similar. In my experience, I haven’t had to adjust formulations for this reason, and by choosing an appropriate flour, such as rice flour, simply replacing wheat flour with a gluten-free flour in the same formulation has been sufficient.

A certain protein content is also beneficial for these cakes to help stabilize the final cake, so I do not recommend making this type of cake with starch alone, unless the formula is modified, for example, by increasing the egg white (albumin) content. It’s true that these cakes, if we simply replace wheat flour with a gluten-free flour, tend to be a bit crumblier, meaning they tend to break more easily. This is because the effect achieved by denaturing wheat protein is not achieved with other proteins. To compensate for this defect, it is common to increase the amount of egg white in formulations. In some cases, the egg quantity is directly increased, indirectly increasing the egg white content. However, it’s not advisable to use an excessive amount of egg white, as it can make the cakes excessively gummy or even tough.

For more information on flour quality control, you can refer to these entries on the blog:

Aspects such as moisture, ash content, particle size, and enzymatic degradation are discussed in this entry.

Those related to starch, here.

For more information on flour quality and other ingredients in cake making, I recommend these articles:

Ingredient functionality in batter-type cake making.

Ingredient functionality during foam-type cake making: A review.

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