A picture of bowls with various types of flour

A Guide to Understanding Flour – Types, Role in Baking, Characteristics, and Essential Knowledge

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Flour is one of the three main components of dough, and arguably the most important. However, with such a wide variety of flour types available, it can be easy to feel overwhelmed and confused – which flour is suitable for each purpose? What distinguishes one flour from another, and why does it matter? This post aims to answer all your questions about flour

Introduction – What Exactly Is Flour?

By definition, flour is a finely ground starchy substance made by grinding the seeds or fruits of various plants, primarily grains. Popular types of flour include wheat, corn, potato, oats, rye, and spelt. Of these, wheat flour is the most commonly used for baking, thanks to its ability to form gluten, which is essential for achieving the fluffy, high-volume baked goods that we are familiar with. Today, thousands of wheat varieties are cultivated worldwide.

The Structure of the Wheat Kernel

The structure of a wheat kernel

Wheat kernels are essentially the seeds of the wheat plant, and they are the part of the wheat plant that is ground into flour. A wheat kernel consists of three main parts: the endosperm, the bran, and the germ.

What we commonly refer to as ‘white flour’ is mainly composed of the endosperm. Wholemeal flours, as their name suggests, are made from the entire wheat kernel, including the bran and the germ, in addition to the endosperm.

The endosperm, which is the white part of the wheat kernel, makes up the majority of it. This is where the white color of flour comes from, as it is mostly composed of starch – typically around 70-75% of the endosperm’s composition is starch. Additionally, protein components are “embedded” within the starch, providing a cohesive element similar to concrete. The two main proteins found in the endosperm are glutenin and gliadin, which are responsible for forming gluten. When flour combines with water, it is the glutenin and gliadin that create the essential gluten bonds needed for baking. In fact, wheat is the only grain that contains enough glutenin and gliadin to produce gluten of adequate quality and quantity for making baked goods.

The germ is essentially the “embryo” of the wheat plant. Under suitable conditions, the germ germinates and grows into a new wheat plant. Wheat germ is a rich source of protein, fat, vitamins B and E, and minerals – nutrients that are crucial for the germination process. It is important to note that although the germ is packed with nutritional value, the proteins it contains are not gluten-forming proteins and do not contribute to the creation of gluten in the dough; In fact, as we will see later, they actually interfere with the formation of gluten. The germ also contains glutathione, a substance that acts as a dough softener or “natural” dough improver (more on that later).

The bran is the protective outer covering of the wheat kernel, often darker than the endosperm (although some wheat varieties have a lighter bran). It is a valuable source of dietary fiber, making up about 42% of its composition. Additionally, the bran contains protein, fat, vitamin B, and minerals. Similar to the germ, the proteins in the bran do not contribute to the formation of gluten.

During the process of flour milling, the bran and germ are separated/removed, leaving only the endosperm. What we commonly refer to as “white flour” or simply “flour”, is in fact the endosperm of the wheat kernel that has been separated from the bran and germ, and subsequently ground into powder.

Classification and Types of Wheat

Before we proceed, it is important to clarify certain terminology:

There are two main ‘categories’ of wheat:
1. “Common wheat” or “bread wheat” (Triticum aestivum), which is used to produce all types of “regular” flour.
2. Durum wheat (Triticum durum), which has different characteristics and is yellow in color. It is primarily used to produce pasta flour, and is commonly known as semola or semolina.

Bread wheat, which is milled to produce “regular” white flour that we commonly refer to as “flour,” comes in varying levels of protein content, ranging from 7% to 14%.

It is important to note that in Italy and France, durum wheat is referred to as “hard” wheat, while bread wheat is referred to as “soft” wheat. However, in the US (as well as in other European countries such as the UK and, to some extent, Germany), the classification of soft/hard wheat is slightly different and is divided into three types:
(1) Durum wheat
(2) Soft wheat (low protein content)
(3) Hard wheat (medium to high protein content)

The table below provides a clearer understanding of the semantics:

Italy, FranceUnited States, United Kingdom, Germany
Hard wheat (refers exclusively to durum wheat)=Durum wheat
Soft wheat (refers to any type of wheat that is not durum)=Soft wheat (low protein content) OR hard wheat (medium to high protein content)

To simplify things, when I refer to soft/hard wheat in the rest of this post, I am using the AMERICAN terminology.
Unless otherwise mentioned, when I say HARD wheat, I refer to bread wheat, with a medium to high protein content; Similarly, when I say SOFT wheat, I am referring to bread wheat, with a low protein content.
Durum wheat is a separate category altogether.

I have chosen to use the American terminology because I believe it will make it easier for readers and bakers to understand the distinctions between different types of wheat and flour. However, if you live in Italy/France and come across the term “hard wheat,” do know that it refers to durum wheat.

When discussing “strong” and “weak” flours, we are referring to the protein content of the flour, as well as its ability to form gluten. Weak flours contain less protein (gluten), while strong flours contain more protein (gluten).

Wheat can be classified into five main varieties (please note that this classification is specific to the US, but is also relevant to other regions around the world):

1. Hard Red Winter wheat (HRW): This type of wheat has a medium-high protein content and is primarily used for bread flour production.
2. Hard Red Spring wheat (HRS): This type of wheat has a high protein content and is used for making high-gluten flour.
3. Soft Red Winter wheat (SRW): This type of wheat has a low protein content and is mainly used for making cake and pastry flour.
4. Hard/soft white wheat (winter and spring): This variety allows for obtaining a white-colored crumb even when grinding wholemeal flour. It is used in the production of noodles, pastries, cereals, crackers, and more.
5. Durum wheat (and also red durum wheat, mainly used as fodder).

In general, flours intended for bread baking are milled from hard wheat varieties. Hard wheat has a medium-high protein content, whereas soft wheat has a low protein level. Additionally, hard wheat kernels often contain a higher level of carotenoid pigment, giving the flour ground from them a creamy color compared to the whiter color of soft wheat.

Flours milled from hard wheat will feel somewhat coarser and “grainy” due to their hard husk, making them more difficult to grind. This granularity also means that hard wheat flours are less likely to clump together, making them harder to compress. When poured, hard wheat flours have a smooth and continuous flow. The coarser grain size of hard wheat flours also makes them more suitable for use as bench flour.

Soft wheat flours often produce a weaker gluten network, making them suitable for making pastries that require a soft texture such as cakes, cookies, and more.

It is important to note that the quality of flour can vary significantly, even within each category, due to factors such as climate, geography, soil, and crop variety. In fact, the same type of wheat can exhibit different characteristics when grown in different locations or even at different times in the same location. This is why flour mills often blend multiple varieties of wheat, or the same variety from different regions and growing areas, to ensure consistent product quality throughout the year.

How is Flour Produced

The production process of flour, specifically grinding, serves two main purposes:
(1) To separate the endosperm from the bran and germ
(2) To grind the endosperm into a powder

Ideally, the goal during the grinding process is to separate as much endosperm as possible while minimizing damage to the starch granules within it. However, achieving this is not simple; Despite the fact that the endosperm accounts for approximately 85% of the wheat kernel’s composition, the average extraction rate of wheat (the amount of flour actually produced) is about 72%; In other words – out of every 100 grams of wheat, only 72 grams of flour are obtained.

A simplified diagram of the flour milling process
A simplified diagram of the flour milling process

The production process is conducted as follows:

1) The flour mill selects wheat varieties (or a blend of different wheat varieties) based on the desired flour characteristics
2) The wheat undergoes cleaning to remove foreign objects such as weeds, insects, small stones, etc
3) The husk of the wheat kernel (the bran) is softened to achieve the optimal moisture level for grinding (about 16%). This softening process helps achieve a flexible bran that can be more easily separated during grinding.
4) The clean and softened wheat is then passed through grinding rollers, which break and “crack” it to separate as much of the endosperm as possible from the bran and germ.
5) The endosperm is separated and “purified” from the bran and germ using sieves and air currents. This process yields three products: coarse granules that contain bran and endosperm together, coarse endosperm granules without bran, and fine endosperm particles, which are essentially flour.
6) The coarse endosperm granules are ground into flour by passing them through a series of specialized rollers.

Steps 5 and 6 are repeated multiple times until most of the endosperm is extracted and ground into flour.

7) The flour is either naturally aged (oxidized) by storing and exposing it to the air for 8-10 weeks, or artificially aged using oxidizing agents.
8) If necessary, additional ingredients are added to the flour based on the requirements of the final product (more details on this later). Then, the flour is packaged and stored before being distributed.

Types of Flour

Bread Flour

Bread flour is made from wheat with a medium-high protein content, and typically has a protein content of 11-13.5%, which forms good quality gluten.

There are no specific criteria for flour to be classified as “bread flour,” but typically, bread flours have a relatively high protein content that is suitable for making bread.

High-Gluten Flour

High-gluten flours are made from wheat which has a high protein content. They typically contain a very high protein content, usually between 13-15%. In addition, some high-gluten flours may contain flour additives or baking improvers that enhance the gluten structure even further.

Cake/Cookie/Pastry Flour

This flour is made from wheat with a low protein content. It usually contains between 7-9.5% protein and is mainly used in making pastries that need a soft texture, like cakes, cookies, and danishes.

All-Purpose Flour

All-purpose flour, as the name suggests, is a versatile type of flour that can be used for various purposes. Unlike other specialized flours, it does not excel in any particular parameter, which is not necessarily a disadvantage. Generally, all-purpose flour contains 9.5-11.5% protein (although this may vary among different flour mills). It is commonly produced by blending wheat with varying protein levels to achieve the desired protein content in the flour.

Whole Wheat (Wholemeal) Flour

Wholemeal flour, as the name suggests, is made by milling all three parts of the wheat kernel: the bran, the germ, and the endosperm. It can be milled to different consistencies, from coarse to very fine. Generally, wholemeal flour have a shorter shelf life compared to white flour because the bran and germ have a high-fat content that can oxidize and turn rancid when exposed to air.

Standard wholemeal flour contains a relatively high amount of protein (11-14%). However, using it does not result in the creation of more gluten compared to bread flour with a lower protein content; This is due to several reasons:

1. The “extra” protein in whole wheat flour, which comes from the bran and the germ, does not contain gluten-forming proteins (glutenin and gliadin)
2. The sharp bran particles in whole wheat flour actually damage the gluten structure by physically cutting the gluten bonds that are formed
3. The germ in the wheat kernel contains components that interfere with gluten development

This means that using whole wheat flour for baking will yield a completely different final product compared to using white flour. Doughs made from 100% wholemeal flour will be very dense, with a coarse texture, a dark color, and a stronger flavor compared to doughs made from white flour.

Durum Flour

Durum flour is made from durum wheat, a type of hard wheat that is yellow in color. The scientific name for durum wheat is Triticum Durum, and, as mentioned before, it is a distinct variety of wheat.

Durum wheat has an exceptionally hard kernel, harder than “regular” hard wheat. It also contains a high protein content, approximately 12-15%, and is rich in carotenoid pigment, which gives it its golden-yellow color.

The gluten formed from durum wheat is shorter compared to other varieties of wheat, which results in a tougher and chewier texture. This characteristic makes it especially well-suited for pasta production.

The Role of Flour in Baking

Flour, along with eggs, is one of the two ingredients that give structure to baked goods. This structure allows baked goods to gain volume during fermentation & baking.

The structure provided by flour relies on two main components: gluten and starch, and the dominance of either component in providing structure depends on the type of baked good and flour used. For example, cake flours barely form any gluten, so starch becomes the primary contributor to the structure of the baked goods. On the other hand, in baked goods with low dough hydration, such as pie crusts or cookies, gluten becomes the main structural element due to the low water content, which prevents the starch from fully gelatinizing during baking.

Interestingly, even in baked goods that require a strong gluten structure such as breads, gluten is not necessarily the most crucial component in providing structure. In bread, for example, both gluten and starch play significant roles in giving it its structure; Gluten creates an elastic structure during fermentation, allowing the trapping of gases and the physical rise in volume, while starch gelatinazation plays a vital role during baking.

The Role of Starch in Baking

Starch has several important roles in baking:

1. It provides structure and texture.
2. As the main component of flour, starch is responsible for most of the water absorption in the dough. It can absorb between a quarter to half of its weight in water.
3. Damaged starch, whether naturally occurring in flour or resulting from milling, allows amylase enzymes to convert the starch into sugar. This sugar serves as a food source for the yeast.
4. Starch “dilutes” the gluten, preventing the baked good from becoming excessively hard and chewy.
5. During baking, starch undergoes a process called gelatinization, absorbing water from the gluten present in the cell walls, causing the gluten to “dehydrate” and harden. The gelatinization process is what prevents the baked good from “collapsing” as it cools.

The gelatinization process occurs when starch is exposed to hot water (over 60C/140F). During this process, starch absorbs water and expands, creating a gel-like texture. The trapped water between the starch molecules is what gives the baked good its soft and ‘moist’ texture.

As the baked good cools down and time passes, the starch molecules gradually “uncurl”, allowing the trapped water to evaporate. This evaporation is responsible for the baked goods drying out and losing their softness over time. Eventually, the molecules align completely, resulting in a completely hard and dry texture.

The Role of Gluten in Baking

Gluten is the most important component in flour because it provides the dough with its structure and enables it to rise and expand in volume. Considering its importance, I will not delve into further details here. For a comprehensive discussion on gluten, please refer to the dedicated entry about gluten in the Encyclopizza.

The Main Characteristics of Flour

Technical specifications of a flour
An example of a technical specification sheet for flour

Each type of flour has distinct characteristics that arise from the composition and properties of the wheat used for its production. Apart from protein content, there are other parameters that can only be assessed by examining the technical data provided by the flour mill. This information is not always disclosed to the public and is sometimes available on the mill’s website.

The following sections will discuss the main characteristics of flour.

Protein Content

One aspect that greatly interests us as bakers is the protein content in flour, particularly that of gluten-forming proteins (glutenin and gliadin). Generally, glutenin and gliadin make up about 80% of the proteins in the endosperm. Therefore, when discussing white flour, the total protein content provides us with a reliable indication of the “gluten potential” of a flour, as a higher protein content typically corresponds to a higher content of gluten-forming proteins.

The proteins present in the flour, including those that do not form gluten, also contribute to the flour’s ability to absorb water. Approximately one-third of the water in the dough is absorbed by proteins, while another half is absorbed by starch, and the remaining third is absorbed by pentosan gum, a type of polysaccharide.

While starch can absorb between a quarter to half of its weight in water, the proteins in flour can absorb 1-2 times their own weight in water. Therefore, even small changes in the protein content of the flour can significantly impact its water absorption capacity. This allows us to determine the flour’s water absorption capacity by examining its protein content – the higher the protein content, the greater the water absorption capacity.

However, it is important to note that when it comes to gluten, the total protein content in the flour, does not necessarily reflect the quality of the protein. There may be cases where a flour has a high protein content, but the resulting gluten is of low quality, compared to a flour with lower protein content but higher protein quality.

The classification of flours based on their types and protein content can be broadly categorized as follows:

Flour TypeProtein Content
Cake Flour8.5% or lower
Pastry Flour8.5-9.5%
All-Purpose Flour10-11%
Bread Flour11-13%
High Gluten Flour13% or higher

In general, the protein content of wheat is directly related to the hardness of its kernel. Wheat with a hard kernel (“hard wheat”) typically has a medium-high protein content, while wheat with a soft kernel (“soft wheat”) has a low protein content. When baking bread & most styles of pizza, it is generally preferable to use flour with a medium-high protein content. 

In addition to the variety of wheat, the protein content in both wheat and flour is greatly influenced by growing conditions and weather; In fact, weather conditions have a greater potential impact on protein content than the type of wheat itself. For example, cold weather or a rainy season can both result in wheat with lower protein content.

Water Absorption

The water absorption capacity of flour, as specified in its technical specifications, refers to the percentage of water needed (relative to the weight of the flour) to achieve an optimal dough consistency for baking. This measurement is obtained through a laboratory test called the Farinograph.

It is important to note that this value is relative, and does not reflect the actual water absorption capacity of the flour in practical dough-making scenarios. Instead, it serves as a comparative figure obtained through a specific laboratory test, allowing for comparisons between different flours. For example, a flour with a water absorption capacity of 60% will be able to absorb more water compared to a flour with a water absorption capacity of 55%, however, it does not mean that both flours can only absorb up to the specified water absorption value given in the technical data.

Generally, the water absorption capacity of most bread flours falls within the range of 57-65%. While there are other factors that can influence the water absorption capacity of flour, such as the ash content, a higher water absorption capacity is often associated with a higher protein content.

Amylase, Enzymatic/Diastatic Activity of Flour, and Falling Number

Alpha-amylase is a crucial enzyme found in flour that directly affects the quality of dough and baking. Its main function is to convert starch into sugars, which serve as a food source for yeast activity. Furthermore, these sugars contribute to the browning of the dough during the baking process as residual sugar in the dough.

Here is a brief explanation of how this process, also known as, diastatic activity (or enzymatic activity) occurs:

1. Flour is mainly composed of microscopic starch granules, each containing long starch molecules.
2. During the milling process, some starch granules become damaged, exposing them to the action of the alpha-amylase (α-amylase) enzymes.
3. Alpha-amylase enzymes break down the long starch molecules into medium-sized molecules, forming a carbohydrate called dextrin.
4. Subsequently, beta-amylase (β-amylase) enzymes target the dextrin molecules and convert them into a disaccharide called maltose.
5. Yeast then breaks down maltose into glucose, which it consumes during the fermentation process. Additionally, maltose and glucose accumulate in the dough as residual sugar.

As can be seen, the role of amylase enzymes in yeast’s food production is crucial. Within this process, alpha-amylase plays a vital role – without the activity of alpha-amylase, the beta-amylase enzymes will not be able to sufficiently breakdown starch on their own.

The glucose produced during this process accumulates as residual sugar in the dough. These sugars are responsible for the browning of the dough during baking through the Maillard reaction; Therefore, the alpha-amylase activity in the flour also affects the degree of browning during baking.

The main factor that affects alpha-amylase levels in wheat is its stage in the life cycle. “Young” wheat has low levels of alpha-amylase, while sprouted wheat has very high levels. Other factors that influence alpha-amylase levels include the type of wheat and its growing conditions.

In a typical scenario, when wheat reaches maturity, it enters a dormant state. However, if the wheat undergoes germination due to factors such as sub-optimal storage before milling or late harvesting, the level of alpha-amylase increases significantly (up to 5000 times compared to dormant wheat).

Using flour with high levels of alpha-amylase can result in excessive production of dextrins in the dough, exceeding the capacity of beta-amylase to break them down into maltose, making the dough sticky and difficult to handle, and the crumb of the baked good unchewable. In case this happens, there is no solution other than switching to a different flour.

To prevent wheat from entering a germination state, it is generally harvested when alpha-amylase levels are very low. As a result, it is often necessary to artificially add alpha-amylase to the flour during its production process.

Falling Number

The method used to measure the level of alpha-amylase in flour, also known as diastatic/enzymatic activity, is called Falling Number (FN). FN values are measured in seconds and are inversely related to the alpha-amylase concentration in the flour; In other words: a lower FN value indicates higher diastatic activity, and vice versa; Flours with high diastatic activity will have low FN values, while those with low diastatic activity will have high FN values.

FN values range from 60 (indicating very high diastatic activity) to 400 (indicating very low diastatic activity). Standard bread flours typically have a FN value of 220-260.

The table below presents a summary of FN values:

Falling NumberComments
150 and belowVery high enzymatic activity. A flour with such a high FN is milled from sprouted wheat. Using this flour will result in a sticky crumb with an underbaked texture. This flour is not suitable for baking unless it is mixed with another flour that has a higher FN value
150-220higher than normal enzymatic activity. The flour requires “correction” through mixing with other flour or the use of specific leavening and baking techniques
220-280Ideal enzymatic activity for most baking purposes
280 and aboveLow enzymatic activity. Ideal for baking at high temperatures (350°C/660°F and above)

Damaged Starch

Damaged starch plays a significant role in the context of amylase, fermentation, and dough behavior. As previously mentioned, alpha-amylase enzymes primarily act on damaged starch in flour because it is “easier” for the enzyme to work on; Therefore, the higher the amount of damaged starch in the flour, the more effectively the alpha-amylase enzymes can function.

If a flour contains excessive levels of damaged starch, it can yield similar outcomes to flour with a high amount of alpha-amylase, as explained in the previous section (sticky dough & crumb). On the other hand, if the flour has too little damaged starch, the yeast will not have enough food (because of limited starch breakdown into sugars), leading to inadequate fermentation of the dough.

In addition to its role in enzyme activity, damaged starch also has the ability to absorb much more water compared to intact starch granules.

Because the endosperm of hard wheat is tougher and more “brittle” than that of soft wheat, the milling process of hard wheat often results in a higher percentage of damaged starch compared to soft wheat. A standard damaged starch content in flour is 5-8%.

Protease Enzymes

Another important enzyme found in flour is protease. Protease enzymes, also known as ‘proteases’, naturally occur in flour and act as dough softeners/reducers. They do this by breaking down the gluten bonds and degrading the gluten-forming proteins through a process called proteolysis. Protease enzymes work from the moment the dough is kneaded until baking, breaking down the gluten bonds and making the dough softer and more extensible.

Protease enzymes play a crucial role in the fermentation process. These enzymes are responsible for making the dough more extensible, less resistant, and giving it a softer texture that is easier to work with. However, if the protease enzymes are allowed to work for too long, they can break down excessive amounts of gluten in the dough. This leads to a weak gluten structure, reduced elasticity, a wet and sticky dough that tears easily, and limited oven spring; In other words – an over-fermented dough.

There are dough improvers and other ingredients that “mimic” the action of protease enzymes. These ingredients are added to the flour either during its production or by the baker when mixing the dough.

It is important to note that the action of protease enzymes in the flour is irreversible. Once the dough has reached a state of overfermentation (due to excessive gluten/protein degradation), it cannot be “repaired”, because the gluten-forming proteins have lost their ability to create new gluten bonds.

Ash Content

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%.

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.

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, please refer to this presentation.

Flour TypeAsh Content
Italian
000.55% or lower
00.55-0.65%
10.65-0.80%
20.80-0.95%
Integrale (Whole Wheat)1.3-1.7%
French
T450.45% or lower
T550.45-0.60%
T650.60-0.75%
T800.75-0.90%
T1101-1.2%
T150 (Whole Wheat)1.40% or higher
German
4050.5% or lower
5500.50-0.63%
8120.63-0.90%
10500.90-1.2%
1600 (Whole Wheat)1.2-1.8%
American
Short Patent Flour0.35-0.45%
Medium Patent Flour0.45-0.55%
Long Patent Flour0.55-0.65%
Straight Flour0.6-0.7%
First Clear Flour0.8-1%
Second Clear Flour1% or higher
Whole Wheat Flour1.5-2%

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

Alveograph (W Index)

An example of Chopin Alveograph

The alveograph is a tool used to measure the rheological performance of flour through a specific laboratory test. It primarily evaluates the dough’s ability to withstand fermentation, which indicates the “strength” of the flour, as well as its resistance and elasticity.

Ultimately, the alveograph provides information about the expected behavior of the flour during fermentation. It helps to determine the flour’s resistance to over-fermentation (how “strong” it is) and measures its viscoelastic properties, specifically its extensibility and elasticity.

It is important to note that the Alvograph (and consequently, the W index) was specifically designed for European flours made from soft wheat, with a relatively low protein content. As a result, its use is primarily limited to Europe, particularly France (where it was invented) and Italy; Outside of these two countries, the use (and publication) of the W index is quite rare and mainly restricted to pizza flours (for marketing reasons, obviously).

The reason for this is that when it comes to soft wheat, there is often no direct correlation between the protein content and the quality of the gluten produced. Two flours from different types of soft wheat may yield dough with different properties and strength, even if they have the same protein content; And this is exactly the purpose of the alveograph test (and the W index) – to provide information on the gluten quality of these flours and distinguish between them.

On the other hand, when it comes to hard or stronger wheat, there is an almost direct correlation between the protein content and the quality of the protein (gluten). In general, in flours made from such wheat, a higher protein content translates to more gluten and stronger flour. Therefore, there is no reason (or need) to use the W value in flours milled from stronger wheat.

Additionally, the alveograph is not suitable for testing hard wheat flours with higher protein content because it is specifically designed for European soft wheat; As a result, the alveograph may provide unreliable and inconsistent results when used to test stronger flours. For testing the properties of stronger flours, it is customary to use the Farinograph, which provides more accurate information.

The process for obtaining the alveograph is as follows:
1. A small sample is taken from the dough made with the flour being tested. This sample is then flattened into a disk shape.
2. The flattened sample is attached to a surface and inflated to a dough “bubble” using air pressure.
3. A dedicated device measures the relevant parameters.

The alveograph consists of three values: P, L, and W.

The P value measures dough resistance, indicating the pressure required to pop the dough bubble (indicating the “strength” of the flour).
Flours with a high P value typically have a high protein content.

The L value measures dough extensibility, indicating its ability to stretch.

The P/L ratio represents the viscoelastic properties of the flour’s gluten.
A P/L ratio of 1 indicates a balanced gluten with equal elasticity and extensibility.
A P/L ratio of less than 1 suggests a gluten that is more extensible, meaning it can stretch more easily.
A P/L ratio greater than 1 suggests a gluten that is more elastic and resistant.

The W index, also known as the “bread baking index,” represents the area under the curve (multiplied by 6.54). It indicates the energy required for the dough bubble to burst, or in simpler terms – the strength and resistance of the dough for baking purposes. 

Generally, flours with a higher W index can absorb more water and result in a final product with a larger volume due to stronger gluten. However, it is important to note that this is not always the case, and depends on the specific values of P and L.

W index usually ranges from 45 (indicating very weak flour) to 400 (indicating a very strong flour). The table below summarizes the W index associated with different baking applications:

WComments
120 or lowerVery weak flour. Not suitable for baking
120-160Weak flour. Suitable for baking cakes and cookies
160-250Medium-strength flour. Suitable for baking goods that do not require a strong dough, such as soft rolls/buns and various pastries
250-310Strong flour (typically made from hard wheat or a combination of hard wheat). Suitable for bread making
310 or higherVery strong flour made from hard wheat. Suitable for doughs that require full strength and high elasticity

Flour Treatments, Additives, and Dough Conditioners/Enhancers

In many cases, the flour label will specify additives that were included in the flour at the mill level, commonly known as “dough enhancers” or “dough conditioners”. Some of these additives are also available for purchase by consumers and can be added by bakers when preparing the dough. The types of additives and their quantities are regulated by relevant government ministries, such as health and agriculture. According to the law, flour manufacturers must* indicate on the label if any additives have been incorporated during the flour production process.
* The only exception to this is European flours, including Italian flours. In Europe, there is no requirement to indicate on the packaging the ingredients or dough enhancers that are added to the flour during its production.

It’s important to note that while the word “conditioner” implies a softening agent, the term “dough conditioners” is a general term that refers to all types of dough enhancers, including dough strengtheners, dough softeners, enzymes, maturing agents, and emulsifiers.

Vitamins and Minerals

As we seen previously, the process of milling white flour leads to the loss of many essential nutrients found primarily in the bran and germ of the wheat kernel. To compensate for this loss, certain vitamins and minerals are reintroduced to the flour. This type of flour is known as “enriched flour”.

In order for flour to be classified as “enriched”, it must contain four (type B) vitamins: thiamin, riboflavin, niacin, and folic acid. Additionally, other vitamins and minerals, such as phosphorus, calcium, and iron, can also be added to the flour.

Flour Aging, Oxidizing and Bleaching

Air (or more precisely, the oxygen in the air) acts as an oxidizing agent, and plays an extremely important role in the context of flour; It causes the oxidation of the flour, which has two main effects: (1) it whitens the flour, and (2) it enhances the flour’s ability to form gluten.

How do these two processes occur?
(1) The oxygen in the air oxidizes the carotenoid pigment in the flour (as mentioned earlier, the pigment that gives the flour its creamy color), resulting in a change in its chemical structure and causing it to become whiter.
(2) The oxygen also oxidizes the gluten-forming proteins in the flour, allowing them to form more bonds during the gluten formation process, which leads to stronger gluten. Dough made from oxidized flour is easier to work with, less sticky, less prone to tearing, and enables the preparation of baked goods with a larger volume.

There are two methods of aging (oxidizing) flour: natural aging, and artificial aging using chemical agents.

Natural aging refers to the intentional exposure of fresh (“green”) flour to the air for a period of 8-10 weeks. However, this process has some drawbacks. Firstly, it requires a significant amount of storage space; Secondly, there is a risk of the flour becoming contaminated by insects, bacteria, mold, and rodents; Additionally, the results of natural aging are less consistent compared to artificial aging, and it generally proves to be less efficient in terms of aging the flour.

Artificial/chemical aging is achieved by adding various chemical agents to the flour, either at the flour mill or during dough preparation by the baker. These agents can be classified into three categories:
(1) Whitening agents, which solely whiten the flour
(2) Agents that modify the flour’s properties, either by strengthening or weakening it
(3) Agents that simultaneously affect both aspects

Nowadays, the most commonly used oxidizing agent to strengthen flour is ascorbic acid, also known as vitamin C (labeled E300).

In the past, the most common and effective oxidizing agent (at least in the US) was potassium bromate. However, it has been banned for use in most of Europe due to studies showing its carcinogenic properties (although other studies have shown that the carcinogenic component is no longer present after baking). Flours containing potassium bromate are still available in most of the US (and are especially popular in pizzerias), but they must be clearly labeled on the flour package as “bromated” flour.

Two commonly used agents for bleaching (whitening) flours are benzoyl peroxide and chlorine dioxide. Benzoyl peroxide is highly effective in whitening flour and is used in all types of flour. It is important to note that benzoyl peroxide only whitens the flour, and does not have any additional effects on it.

Chlorine dioxide is “unusual” in this context because, in addition to bleaching the flour, it also significantly weakens the gluten by allowing the starch in the flour to absorb more water, effectively “diluting” the gluten. This is particularly desirable in cake flour.

Enzymes (Alpha-Amylase)

As we have seen, alpha-amylase enzymes are responsible for converting starch into sugars, and are crucial in flour. Normal white flour contains amylase, although usually not at a sufficient level to achieve optimal dough characteristics, such as providing food for yeast and promoting browning during baking.

To achieve proper amylase levels in the flour, the mill can take two approaches:
(1) Adding amylase to the flour during its production. This can be done by incorporating malt (a sprouted grain, typically barley) that is rich in amylase, or by directly adding fungal amylase
(2) Blending different wheat

If alpha-amylase has been added to the flour (using malted barley or enzymes), it will be stated in the list of ingredients on the label, usually as “enzymes” or “barley malt/malted barley”.

In the US, flours treated with the addition of amylase are labeled as “malted flour”. However, it is important to note that this classification is merely semantic – a flour can still have a high natural enzymatic activity without the “artificial” addition of barley malt; Therefore, a flour labeled as “unmalted”, does not necessarily mean it has low enzymatic activity.

It is worth mentioning that in Italy, it is customary to not treat flour with alpha-amylase, resulting in most Italian flours having low enzymatic activity.

Dough Reducers/Softeners

Dough softeners, as their name suggests, speed up the softening of dough by breaking down gluten bonds, similar to the action of protease enzymes (although not exactly the same). Dough softeners are used to achieve a softer and more manageable dough in a shorter period of time. Unlike protease enzymes, which only work during fermentation and take longer to soften the dough, dough softeners start working during the kneading stage. This allows for a reduction in mixing time and improves the workability of the dough.

An example of common dough softeners include L-Cysteine (labeled E920), glutathione (also known as dead/inactive yeast), PZ-44, sorbic acid, and bisulfite.

Additionally, there are other ingredients that serve as dough softeners but function differently from protease enzymes and the dough improvers mentioned above, including starch (potato, rice, or corn starch) and fat (oil, butter, or shortening). These ingredients help soften the dough, although they do not do this by breaking down gluten bonds.

Emulsifiers

Normally, water and oil do not mix and repel each other. Emulsifiers enable the mixture of water and oil, forming an emulsion. Emulsifiers possess hydrophilic (water-binding) and lipophilic (oil-binding) properties that allow them to bring water and oil together, creating a uniform mixture.

Using emulsifiers in pizza dough is generally not advisable; This is because they allow the crust to draw moisture from the toppings during baking, which can result in an undercooked layer of dough known as “gum line”. Instead of repelling moisture from the toppings, the fat in the dough (naturally occurring in the flour or added as part of the dough formula) binds to it, causing moisture to accumulate in the crust during baking – not a desirable thing when making pizza.

Some common emulsifiers include lecithin (labeled as E322), polysorbate-60, and monoglycerides.

Chemical Leavening Agents (Self-Rising Flour)

Artificial leavening agents are chemicals that are used to make the dough rise and increase in volume during baking. The most commonly used type of chemical leavening agent is baking powder, which is a mixture of baking soda (sodium bicarbonate, labeled E500ii) and an acid (usually monocalcium phosphate).

When baking soda comes into contact with an acid, a chemical reaction takes place, and carbon dioxide is produced, which causes the dough to rise. The presence of acid in the baking powder mixture is crucial for this reaction to occur, as baking soda alone cannot produce carbon dioxide without an acid.

One example of a product that contains artificial leavening agents is self-rising flour, which is regular white flour pre-mixed with baking powder.

Vital Wheat Gluten

Vital wheat gluten (VWG) is a cream-colored powder that contains approximately 75% of the “vital” proteins (glutenin and gliadin) needed for gluten formation. The production of VWG involves mixing a dough until it reaches full gluten development, followed by a process known as “gluten washing” to separate the gluten from the remaining dough (mostly starch). Afterward, the resulting gluten is dried and ground into a powder, so what is obtained is a powder that contains gluten-forming proteins that have retained their ability to produce gluten and can effectively “recreate” it.

Flour mills can artificially “strenghten” their flours by adding  gluten to the flour to increase its gluten content, and as bakers, we also have the option of doing this by adding VWG when preparing the dough. Generally, adding 1% VWG will increase the protein (gluten) content of the flour by approximately 0.6%; For example, if a flour has 10% protein and 1% of VWG is added, the final protein content will be 10.6%.

VWG should always be added to the flour, not directly to the water. VWG absorbs water quickly and clumps easily; Adding VWG directly to the water will create “gluten lumps” that will not be properly incorporated into the dough. Therefore, it is always advisable to add VWG on top of the flour.

It is important to note that in certain parts of the world, specifically in Italy and other European countries, regulations do not require labeling the addition of VWG in the ingredients list. This means that for Italian flours, it is impossible to know whether the flour’s protein content is “natural”, or if it has been treated with VWG.

Does Flour Need to Be Sifted?

Unless you want to ensure that there are no non-flour materials (such as insects, sand etc.) due to kosher or other considerations, there is no need to sift flour. Sifting will not increase the flour’s water absorption, and other than removing non-flour materials, it is entirely unnecessary.

*The only exception is when baking cakes – sifting the flour guarantees that no large lumps will form in the batter, which would be challenging or impossible to break down later on.

How to Store Flour

Flour should be stored covered and sealed, in a cool and dry environment.

All types of flour have a limited shelf life. In most cases, flour manufacturers recommend not storing flour for more than six months to a year. The primary process that occurs in flour stored for an extended period is the oxidation of its natural fat due to exposure to air, which can result in a rancid taste and unpleasant aftertastes resembling cardboard.

While wholemeal flours tend to oxidize faster due to their higher fat content from the bran and germ, even the smallest amount of fat found in white flour (about 1%) will eventually oxidize and turn rancid. The change in taste is only superficial and does not necessarily make the flour dangerous or unfit for use and consumption, however, it is advisable to prevent this situation by storing the flour properly.

Additionally, flour is hygroscopic and absorbs moisture from the air; Therefore, it is important to store flour in a dry place to prevent it from absorbing moisture. Moisture absorption can lead to the formation of lumps in the flour, a decrease in its ability to absorb water, and potential problems such as attracting insects, pests, and the formation of fungi and mold.

Storing flour in the refrigerator or freezer is a great and advisable practice, especially for flour that won’t be used for a while. However, it’s important to note that cold flour takes longer to absorb water, which will also delay gluten development during kneading; Therefore, if you store flour in the freezer, it is recommended to bring it to room temperature before using it. Keep in mind that frozen flour takes a relatively long time to thaw completely, so it’s advisable to do this at least a day before using it.

How to Store Bread, Pizza, or Any Other Flour-Based Baked Goods

The primary reason for bread drying out or staling is the loss of moisture. Generally, bread will maintain its properties when stored below 0°C/32°F (freezing) or above 60°C/140°F, but it will quickly deteriorate and dry out if stored in the fridge:

  • At temperatures above 60°C/140°F, heat significantly delays moisture loss.
  • During freezing, the water in the bread turns into ice, aiding in preserving moisture.
  • The low temperature in the fridge “facilitates” the alignment and hardening of starch molecules, resulting in faster moisture loss. As a result, bread stored in the fridge dries out and spoils faster compared to bread stored at room temperature or in the freezer.

Therefore, the most effective method for long-term bread storage is in the freezer, or if it is frequently consumed, in a dedicated bread box. It is advisable to refrain from storing bread in the fridge altogether.

If you’ve already baked bread or pizza and want to keep it fresh for a short time (a few hours at most), you can store it in the oven at a temperature of 60°C/140°F.

Concluding Remarks

If you’ve made it this far, you already know that the world of flour is vast. Different types of flour have their own unique characteristics, which directly affect the end product. The information in this post is comprehensive and might be overwhelming, with some parts being quite technical; However, understanding this information can help you comprehend how flour affects baking and assist you in choosing the most appropriate flour for your specific needs.

At the end of the day, the only way to truly determine whether flour X is better than flour Y for a specific application is through actual baking, as theoretical knowledge alone cannot replace years of hands-on experience in dough preparation and baking. However, gaining knowledge is still valuable; It is important to understand not just the “how” but also the underlying principles. After all, that is what PizzaBlab is all about 🙂


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