What is the W index and how to choose the right flour
All flours are not the same, which is why it is important to use the one best suited for the recipes we want to make from time to time. A very important factor in choosing flour is its strength, that is, its ability to absorb water during kneading and retain carbon dioxide during rising.
This value is determined by the amount of gluten developed by the flour. In fact, the two gluten proteins, glutenin and gliadin, bind together during kneading to form a more or less strong gluten mesh. The former makes the dough elastic and able to hold starches and gases, the latter makes it stretchable.
The dough is then measured in the laboratory using a specific instrument, the Chopin alveograph, which makes it possible to compare the elasticity or hardness of different types of flours and determine their strength index or W index.
All flours are not the same, which is why it is important to use the one best suited for the recipes we want to make from time to time. A very important factor in choosing flour is its strength, that is, its ability to absorb water during kneading and retain carbon dioxide during rising.
This value is determined by the amount of gluten developed by the flour. In fact, the two gluten proteins, glutenin and gliadin, bind together during kneading to form a more or less strong gluten mesh. The former makes the dough elastic and able to hold starches and gases, the latter makes it stretchable.
The dough is then measured in the laboratory using a specific instrument, the Chopin alveograph, which makes it possible to compare the elasticity or hardness of different types of flours and determine their strength index or W index.
The classification of flours
Flours can be classified according to their strength and then chosen according to their characteristics*.
Weak flours (< 180W)
They are suitable for all types of processing that require neither long rising times nor excessive mechanical processing, such as crackers, cookies, breadsticks. They absorb little water during kneading, about 50 percent of their weight, and rise faster because the weak gluten mesh allows gases to escape easily.
Medium flours (180W - 270W)
These are easy to process and suitable for workings that require fairly sustained mechanical processing, the development of a strong gluten mesh, and medium rise times. Ideal for French bread, oil bread or some types of pizza. They absorb 55 percent to 70 percent of their weight in water and are the most commonly used in pizzerias.
Special flours (>350W)
These are made from special grains and are used to strengthen weaker flours or to produce special breads. They absorb up to 90% of their weight in water.
*Values are not exhaustive and should not be taken as units, as gluten qualities may depend on several factors and parameters.
Weak flours (< 180W)
They are suitable for all types of processing that require neither long rising times nor excessive mechanical processing, such as crackers, cookies, breadsticks. They absorb little water during kneading, about 50 percent of their weight, and rise faster because the weak gluten mesh allows gases to escape easily.
Medium flours (180W - 270W)
These are easy to process and suitable for workings that require fairly sustained mechanical processing, the development of a strong gluten mesh, and medium rise times. Ideal for French bread, oil bread or some types of pizza. They absorb 55 percent to 70 percent of their weight in water and are the most commonly used in pizzerias.
Special flours (>350W)
These are made from special grains and are used to strengthen weaker flours or to produce special breads. They absorb up to 90% of their weight in water.
*Values are not exhaustive and should not be taken as units, as gluten qualities may depend on several factors and parameters.
How to choose flour by strength
If we want to choose a flour on the basis of its strength, however, we may have some difficulty, because the W index is not always indicated on the bag. In this case we can rely on the amount of protein, which as we have seen is the main factor in determining the strength of a flour. The higher this value, the greater the suitability for breadmaking.
So if we have protein values around 8-9% we will be dealing with a weak flour, 10-12% is indicative of a medium flour, 13-14% is typical of a strong flour while over 14% characterizes special flours. It should be pointed out, however, that in addition to reading the number of proteins, it is also necessary to consider the type of flour since, with the same amount of protein, flours that belong to different categories develop gluten differently (e.g., whole wheat flours develop a weaker gluten mesh than wheat flours).
Another way to be sure of making the right choice is to rely on the functions indicated on the labels: a pizza flour will have the ideal characteristics for making pizza (medium strength, high extensibility), a cookie flour will be weaker, and so on.
So if we have protein values around 8-9% we will be dealing with a weak flour, 10-12% is indicative of a medium flour, 13-14% is typical of a strong flour while over 14% characterizes special flours. It should be pointed out, however, that in addition to reading the number of proteins, it is also necessary to consider the type of flour since, with the same amount of protein, flours that belong to different categories develop gluten differently (e.g., whole wheat flours develop a weaker gluten mesh than wheat flours).
Another way to be sure of making the right choice is to rely on the functions indicated on the labels: a pizza flour will have the ideal characteristics for making pizza (medium strength, high extensibility), a cookie flour will be weaker, and so on.