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If you’ve ever moved between countries or went to a specialized (online) baking store, you might have experienced it: flour analysis paralysis. There are so many different types of flour out there that it’s hard to decide which one you need. Different names, numbers, and codes which are sometimes the same, and sometimes they’re not. There’s 00, cake, 45, bread, all-purpose, 110, self-raising, or whole wheat flour, to name just a few.
There are a lot of historical reasons behind all these flour naming conventions. For one thing, different countries had different needs and requirements resulting in different legislation, for another, it’s what people are used to. We’ll look at the science of flour to solve the analysis paralysis.
Comparing flour – most important properties
To know what flour is best for your purpose, you need to know how flours can even be different. Therefore, let’s start by refreshing our flour knowledge.
A quick note, in this article we solely discuss flours made from wheat, matters are complicated enough as they are without including any other type.
Variable 1: Wheat type
Wheat flour is made from wheat kernels. The properties of this wheat kernel will determine the behaviour of the flour. There are two specific properties that bakers will be looking for (and they’re slightly related): the protein content & hardness.
Wheat kernels contain a little fat, a moderate amount of proteins (gluten) and fiber and, the major component: starch, a carbohydrate. The fat and fiber content don’t vary as much between wheat types, but the protein and as a result the starch content, do.
Since the protein content is so important for the functionality of the wheat flour, you will often find the protein content mentioned explicitly. The protein solely depends on the wheat that was used to make the flour. The wheat variety, how and where it was grown, and which weather it experienced all impact protein content. Once harvested, the protein content is more or less set. It is not influenced by the production process after harvest.
The protein content of wheat can vary widely, from as low as 6% to as high as 20%, although most commercial wheat flours contain somewhere between 7 and 15% protein.
Protein content is just one of the parameters flour manufacturers test for. They also check for moisture and ash content as well as several other parameters.
Wheat grains can have a range of degrees of hardness. The softer ones, appropriately called soft wheats, can be milled more easily than the harder ones. The harder the wheat the greater the interaction between the protein and starch in the wheat. This makes it harder to separate them well.
Protein content & hardness are related, but not 100% so. A harder flour does generally contain more protein and a softer flour contains less. However, some overlap is possible, that is, some high protein soft wheat flours might contain the same amount as a low protein hard wheat flour.
Starch in the wheat is present in the form of starch granules. These starch granules can break during milling. Since a harder wheat requires more force to mill, the chances of the starch granules breaking are larger in a hard wheat. More damaged starch in flour makes it easier for the flour to absorb water. This is desirable in breads, but less so in cakes.
Variable 2: Processing of the wheat – extraction rate
Once you’ve chosen your wheat type (or you might have blended several wheats) it is time to transform the kernels into flour. How you do this and with which intensity will also impact your flour properties.
A wheat kernel is made up of three sections: the bran, endosperm and germ. The bran, which forms the outside of the kernel, is most rich in fibers whereas the germ contains most protein and fat. All three parts contain a high amount of starch, but the endosperm contains the highest percentage. Therefore, whether you use all parts of the kernel or just the center will determine the composition of your flour.
In order to make flour the wheat kernels are broken down into smaller particles. This is a multi-step process and contains a lot of roller mills to reduce particles as well as sieves to sort all the resulting particles by size.
One of the first steps in milling is to separate the bran, germ and endosperm. They can be recombined later, but are split to continue milling the individual parts to the required particle size. The extraction rate describes the percentage of the original wheat kernel that is used to make the final product.
If the components are mixed together in the same ratio as in which they were initially present in the flour, you make whole wheat flour. This has an extraction rate of 95-100% since you use the whole kernel to make the flour.
White flour on the other hand will have an extraction rate <75%. The bran and germ have been removed.
You will often see that either extraction rate or ash content is used. Both refer to the same distinction. A higher extraction rate results in a lower ash content. The ash content of flours is mostly made up of minerals. Since these sit mostly in the bran, the amount decreases for a higher extraction rate.
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A milled flour can be bleached. This is not done in Europe, but is quite common in the US. Bleaching is done to extent the shelf life of flours. It will delay oxidation and the formation of off-flavours. however, it also impacts the flour behaviour. If you want to bake very sot light cakes for instance using a bleached flour is actually beneficla for your cake structure. two most important variables, there are a few other differences between flours.
Another variable is particle size. Some flour types (e.g. semolina) are deliberately milled to a larger particle size than others. Often this is not indicated very clearly on a pack. Generally whiter flours meant to be used for cakes are milled more finely than let’s say a flour best suited for bread baking.
European flour grades
Now that we know that we need to look for the protein content as well as extraction rate, we can see how this translates into flours. In Europe, flours often contain number codes. There are roughly three different systems that are used in different countries (we’ve split them into Italy, France & Germany). Other systems used in other countries all work similarly.
These numbering systems, as we’ll explain in more detail next, focus on the extraction rate of the flour, thus how it has been milled. It does not have to say anything about the hardness or protein content of the flour. This is often given separately.
In Italy, just like many other continental European countries, flours are divided based on their extraction rate (and thus ash content). Within the soft wheat flour category (hard wheats, like durum have their own category) five types exist. There is whole wheat flour which contain the whole grain. On the other opposite sits 00 flour which has the highest extraction rate. In between the two it goes from 00 to 0, 1 and 2 up to wholemeal flour.
Before diving into this world of flour I always thought that 00 flour is the flour you use for pasta. However, that is not true. you do indeed use 00, but it has to be the hard flour type, not the soft flour one!
French & Spanish flours
The French flour naming system is very similar to that of Italy. It also uses extraction rate to distinguish flour types, but uses different codes. Again, the lower the number, the lower the extraction rate, thus the smaller the fraction of wheat that is kept in the flour. The numbers in the French system rank from 45 to 150, where 150 is wholewheat and 45 is most refined (in between you have 55, 65, 80 and 110). The numbers refer to the dry ash content where 45 would stand for 0,45%.
The Spanish flour is very similar to the French one with slightly different standards used.
Germany & Poland
The German system is very similar to the French. However, it runs from 405 (most refined) to 1600, so they’ve multiplied the French numbers by 10. Poland uses a very similar system. Again, the number refers to the ash content.
British & American flours
As opposed to those number coding systems, the British and Americans use a naming system. Most flours are named with their intended use, e.g. bread flour, instead of a code defining a strict number. We’ll highlight the most important ones.
All purpose & self raising flour
All purpose is a flour meant to be suitable for, exactly, all purposes. Therefore, it has a moderate protein content and extraction rate appropriate for a white flour.
Self raising flour is more British than American. Essentially it is all purpose flour but than mixed with a pre-determined quantity of baking powders to help give that rise in cakes etc.
Bread flour is flour made form a high protein content. It tends to have a very similar extraction rate compared to all purpose flour (so milled in a similar way) but it’s made from different wheats.
Cake flour has a lower extraction rate than all purpose flour. You could compare all purpose flour with the French 55 flour, whereas cake flour is more comparable to the 45 type. Also, cake flour is maede from wheat types that have a lot lower protein content.
Online you will find a lot of ways to make your own cake flour. Generally, it involves mixing cake flour with corn starch. Whereas this does lower the overall protein content, it does not give you the same xtraction rate a scake flour has. Therefore, you will continue to notice the difference and it is not a one on one replacement in most applications.
Guide to choosing the right flour
Step 1: decide whether you need a high or low protein content. Cakes, cookies & scones can do well with a low(er) protein content whereas pasta and bread work better with a higher protein content.
Step 2: determine how delicate your product needs to be. A whole wheat flour will always result in a less fine, airy product. It will be more dense and will require more water. However, it does contain more fiber.
Which flour do you need?
Of course, if in your country the flours have the name of their application in them, choosing is easy. In other cases it can be harder though, so we’ve put some tips together.
In order to make bread you need gluten. Gluten are what helps to create the flexible, stretchy bread dough. Therefore, when you’re looking for a bread flour, you tend to look for one with a high protein content. That said, in a lot of cases an average protein content works fine as well.
Apart from the higher protein content, the extraction rate depends a lot on the type of bread you’re making. Of course you need whole wheat flour for a whole wheat bread. It doesn’t bring a big benefit to take a highly extracted flour for white bread, a regular white flour (extraction rate around 70%) is just fine.
For pastries like pie doughs an all purpose flour with low gluten content generally work well. You don’t want to develop a lot of gluten in most cases, so a lower protein content will help with that.
We tested three types of flour: all purpose, whole wheat pastry flour (a special whole wheat flour made from soft wheat) and cake flour to make a chocolate tart shell. All three turned out fine. however, we did notice that the cake flour required less moisture than the other two and the whole wheat version needed a little extra (as expected). The final results were quite similar though!
For making a pasta you should be looking for a flour with a high protein content and preferably made from a hard wheat. Also, you want a pure flour, so with a lower extraction rate. You will often find that 00 Italian flours are recommended. However, take care, a 00 flour can be made from both a soft and hard flour. Ensure the 00 flour you choose is the one suitable for making pasta.
Cakes, and scones, do not need gluten, the less the better, so look for a flour with a low protein content. Soft flours work best and you want a flour with a low extraction percentage (which also decreases protein content further). Patent flours are often a good choice or of course cake flours.
We did an experiment in which we made lemon cupcakes (from Yotam Ottolenghi’s Sweet) using three types of flour: all purpose, bread & super-fine cake flour. All three recipes were identical, we did not adjust anything if we thought one flour might need more liquid than another for instance. The final cakes looked very similar, no big differences there. However, when taking them out of the pans, the cake flour ones clearly were a lot more delicate and soft. A blind taste test showed that the cake flour was the lightest and airiest, followed by he all purpose and bread flour. The bread flour cupcake tasted a little dry even, exact as we expected!
Ameden, K. (King arthur flour), How to substitue read flour for all purpose flour, 2016, link
Arias, T. (Handle the Heat), Cake flour 101, link
De kooktips, Meel en bloem – uitmalingsgraad tabellen, link
Doves Farm, Types of flour, link ; has a nice graphic showing the difference between soft and hard flour
Khan, Khalil. Wheat: Chemistry and Technology. United States, Elsevier Science, 2016, chapter 3 & 5, link
Kinoshita Flour Mills, Milling, link ; provides a good schematic overview of the milling process
Kookwinkel blog Oldenhof, Bloem of cakemeel, 2016, link
Sourdough Library, Ash content of American and European flour types
The Conversation.com, Science in the kitchen: the fresher the flour, the softer the cake, 2017, link ; Did you know that fresher flour can lead to a better cake?!
The Fresh Loaf, link ; post shows a nice overview of the milling process
Weekend Bakery, Understanding flour types, link
Zanirato, S., The European Flour Millers, Wheat Flour standards in European Union, 2013, link ; clarifies the different European standards