Flour W Rating Explained: What It Measures, Its Limitations, and Whether Knowing It Is Actually Necessary

The W rating in flour, also known as the W index, is often regarded as a key factor when choosing pizza flour. In this article, we explore its origins, what it actually measures, its limitations, and why it might not be as critical for pizza makers as many believe

What Is the W Rating in Flour

Let’s begin with the basics: what does the W rating actually indicate?

Essentially, the W rating reflects the strength of the flour, specifically how resistant the resulting dough is to over-fermentation. In simpler terms, it shows how well the dough can withstand fermentation before the gluten structure becomes too weak for baking – nothing more, and nothing less.

The W rating is determined through a laboratory test known as the Alveograph test.

Generally, a higher W rating suggests a stronger gluten, which theoretically makes the dough more “resistant” to longer fermentation.

And this is where things start to get complicated:

The fermentation process, specifically the action of protease enzymes breaking down gluten in the dough (thereby weakening it), is influenced by various external factors. These factors are not necessarily directly related to the flour itself, or if they are, they may not be reflected in the W rating.

Factors such as fermentation temperature, amount of yeast, enzymatic activity in the flour, salt level in the dough, and final dough temperature – all play crucial roles in achieving successful fermentation and preventing over-fermentation.

To conclude, the purpose of the W rating is to indicate the dough’s resistance to over-fermentation. However, accurately conveying this information without considering all of the above factors is practically impossible, which limits the value of the W factor.

Will a flour with a W rating of 320 be “stronger” than a flour with a W rating of 250, all things being equal? Most likely. However, it is crucial to understand that the W rating is not the sole determining factor for choosing a flour, and it should not be considered the ultimate measure of dough strength.

Flour W Rating and Type of Wheat

It is important to note that the alveograph (and consequently, the W rating), was specifically designed for European and Italian flours made from soft wheat, which typically has a relatively low protein content. As a result, its use is primarily limited to Europe, particularly France (where the alveograph was invented) and Italy.

Outside of these two countries, the use (and publication) of the W rating is quite rare and mainly restricted to pizza flours for marketing purposes.

The rationale behind this is that, with soft wheat, there is generally no direct correlation between protein content and the quality of the gluten it produces. Two flours from different types of soft wheat may yield dough with varying properties and strengths, even if they have the same protein content. The alveograph test and the W rating aim to provide information about these flour properties and distinguish between them.

Conversely, for hard wheat (or wheat with a high protein content), there is typically a direct correlation between protein content and gluten quality. In general, flours made from hard wheat translates to more gluten and stronger flour. Therefore, there is no reason, or need, to use the W rating for flours milled from stronger wheat, as the protein content alone is sufficient to determine the flour’s strength.

Furthermore, since the alveograph was primarily designed to evaluate European soft wheat, it is not suitable for assessing the strength of hard wheat flour or flours with higher protein content (for reasons beyond the scope of this article). As a result, using the alveograph with such flours yields unreliable and inconsistent results, which is why it is not commonly used outside of France and Italy. To evaluate the strength and properties of flour made from stronger wheat, the Farinograph is typically used, as it provides more accurate information.

Thus, the W rating is primarily used in Italy and France, with rare usage outside these countries, as it is not necessary, useful, or reliable for evaluating the quality or strength of flour.

In conclusion, the W rating was established as a general indication of the strength of French and Italian flours because their strength cannot be accurately estimated based solely on protein content.

Therefore, if you are using Italian or French flour, the W rating can indeed be useful in estimating the flour’s strength (with an emphasis on “estimating”). On the other hand, the strength of non-European flours, or those milled from non-European wheat, can often be directly inferred from their protein content, making the W rating irrelevant and unnecessary (and it is usually not available either, as these flours do not undergo the alveograph test).

Flour W Rating and Fermentation Durations

Another important consideration regarding the W rating is its alleged correlation with fermentation times.

It is common to come across the table below (or a similar version of it) in various Italian sources. This table attempts to establish a correlation between different W ratings and fermentation durations.

When discussing the W rating in relation to fermentation durations, it is important to clarify that these durations refer to fermentation at room temperature, rather than cold fermentation. What is considered “room temperature”? Generally, it refers to any temperature ranging from 16-30°C/60-86°F. This makes the link between fermentation times and the W rating even more tenuous, as temperature is the primary factor driving fermentation.

The chart provides a rough illustration of the correlation between the W rating and fermentation duration for both room temperature fermentation and cold fermentation. The numbers for the cold fermentation column (which I have added) reflect the fact that dough fermentation occurs at a much slower pace when it is cold fermented.

Note that this chart is for illustration purposes only and should be used only as a very broad and general reference. In practice, it is entirely possible to use weaker flour for longer fermentations and vice versa, as long as the fermentation and dough-making processes are correctly managed (up to a certain point; using very weak flour for an extended room temperature fermentation would not be a good idea).

Additionally, as noted, and contrary to common belief, it is not necessary to use strong flour or flour with a high W rating when cold fermenting dough, because the fermentation process during cold fermentation is much slower. In this context, medium-strength flours can work just fine, depending on the total fermentation duration and the correct dough management process.

The same principle applies to preferments that are cold-fermented.

Flour W Rating: Concluding Remarks

To conclude, the W rating is a technical measurement that indicates the strength of flour and its resistance to over-fermentation. However, it’s important to recognize that the W rating is derived from a specific laboratory test conducted under controlled conditions that may not reflect real-life scenarios.

Consequently, knowing the W rating does not necessarily contribute to making better pizza, and in most cases, it’s unnecessary to dwell on it or place too much emphasis on it.

Moreover, for non-French and non-Italian flours, the W rating holds little significance. Its usefulness is primarily limited to French and Italian flours.

If you live outside of France or Italy and are seeking locally produced flour, it’s unlikely you’ll find published W ratings for these flours, as they are generally not considered reliable. Mills outside of France and Italy typically do not utilize or publish W ratings, unless for marketing purposes.

Instead of focusing on the W rating, a more effective approach is to master your dough management process. This includes maintaining an ideal final dough temperature, adjusting yeast quantities based on fermentation temperature and duration, and following proper fermentation techniques for both room temperature fermentation or cold fermentation.