The protein content of flour plays a crucial role in every stage of sourdough bread-making, from cultivating a lively starter to baking the perfect loaf. It influences key aspects such as gluten development, fermentation, crumb texture, and hydration levels. By understanding how protein impacts both your starter and dough, you can achieve consistent results and gain confidence in experimenting with various flour types and flavors.

This article explores how protein content affects sourdough baking and examines the role of different flour types in dough development. Additionally, we’ll guide you through the process of calculating protein content for both individual flours and blends. To make things even easier, we’ve included handy calculators to simplify the math. Whether your goal is a tangy, robust starter or a loaf with a light, open crumb, understanding protein content is key to mastering the art of sourdough baking.

How Protein Content Affects Sourdough Starter, Dough and Bread

The protein content of flour is directly linked to its ability to form gluten, the elastic network that traps gas during fermentation. High-protein flours, such as bread flour with 12-14% protein, create a stronger gluten network when hydrated and kneaded. This gluten structure supports well-risen loaves with a chewy texture and an open crumb. In contrast, flours with lower protein levels form weaker gluten networks, resulting in softer, denser bread with less rise.

It's important to note that high-protein whole grain and high-protein white flours behave differently. Whole grain flour contains bran and germ, which interfere with gluten formation by physically breaking through the gluten strands.

Below, we’ll explore the differences between low-protein and high-protein flours in more detail. Understanding these differences will enable you to make informed adjustments to hydration levels or fermentation times, helping you achieve desired texture, crumb structure, and crust.

Low-Protein Flour (8-10% Protein)

Sourdough Starter
Low-protein flours, such as all-purpose flour, produce starters that tend to be looser and more liquid. The gluten network is weaker, and as a result, starters made with low-protein flour may require more frequent feedings. This is because the weaker gluten structure can't hold its shape during extended fermentation.

Hydration
Low-protein flours absorb less water, which means the dough will need less hydration. If too much water is added, the dough becomes sticky and difficult to manage. Reducing hydration helps achieve a more manageable dough.

Fermentation
Starters and dough made with low-protein flour ferment faster, as the weaker gluten structure allows gases to escape more quickly. However, this can also lead to overproofing if not carefully managed. Low-protein doughs tend to be more prone to collapsing after extended fermentation due to the lack of structural integrity.

Dough Structure, Texture, Crumb, and Crust
The dough made with low-protein flour lacks elasticity and extensibility. It will produce a tender, soft crumb but it won’t develop a chewy texture or significant rise. The crust is typically thinner and less crisp than that of higher-protein flours. The final bread will be soft, with a denser crumb and minimal air pockets.

High-Protein White Flour (12-14% Protein)

Sourdough Starter
High-protein white flours, such as bread flour, create a thicker, more elastic sourdough starter. The strong gluten network provides structure and stability, allowing the starter to trap gases efficiently. This results in a more active and bubbly starter that holds its shape during extended fermentation. When the starter is well managed and healthy, it can easily tripple in volume at peak activity.

Hydration
High-protein white flours absorb more water, making them suitable for higher hydration doughs. This will allow you to achieve an open crumb with larger air pockets.

Fermentation
High-protein white flours support long fermentation times due to the strong gluten network, which retains gas during fermentation and prevents collapse, making the dough more resilient during proofing and baking. This extended fermentation allows for complex flavour development.

Dough Structure, Texture, Crumb, and Crust
The dough made with high-protein white flour has excellent elasticity and strength, making it easier to handle and shape. The crumb should be open and airy, with large air pockets, while the texture is chewy. The crust is typically thin, crispy, and well-formed, providing the ideal balance of flavour, texture, and structure for a classic sourdough loaf.

High-Protein Whole Grain Flour (12-14% Protein)

Sourdough Starter
Whole grain flours, such as whole wheat, create a more active starter compared to white flours due to the nutrients present in the bran and germ. However, because of the bran’s physical disruption of gluten formation, the starter may still have a looser, runnier consistency compared to starters made with white flour. The fermentation process tends to be faster as well.

Hydration
Whole grain flours absorb more water due to their higher fiber content, so doughs made with these flours require higher hydration levels than white flour doughs. This makes the dough stickier and harder to handle, requiring adjustments to achieve the right consistency.

Fermentation
Whole grain dough ferments more quickly because the bran and germ contain more enzymes that accelerate fermentation. However, this can also lead to overproofing if not managed carefully. The increased enzymatic activity means whole grain doughs can develop more flavour in less time, but careful attention is needed during proofing to avoid over-fermentation.

Dough Structure, Texture, Crumb, and Crust
Whole grain doughs tend to have a denser structure because the bran interferes with gluten development. The crumb will be more compact, with fewer large air pockets, and the texture is often more earthy and robust compared to white flour breads. The crust is thicker and chewier. While whole grain flours lack the extensibility of white flours, blending them with high-protein white flour can help improve dough strength and structure while retaining the rich, earthy flavor of the whole grain.

For most sourdough breads, flours with 12-14% protein are ideal for achieving optimal gluten development and structure. Adjust hydration levels and fermentation times based on the protein content of your flour, and consider blending flours to achieve your desired flavour and crumb structure.

How to Calculate Protein Content

To calculate the protein content of the flour in percentages, first, locate the nutrition label on the flour pack. If protein content is given per 100g serving, the protein content in percentages will be the same number as the protein content in grams. For example, if the label says 12g of protein per 100g of flour, then the protein content is 12%.

Whilst most flour packaging will list the amount of protein per 100g serving, there are instances, especially in America, where the serving amount is different. If the protein content is given for a serving size other than 100g, you can use a quick calculation. 

For example, if the label states there are 4g of protein in a 30g serving, use the formula below:

Protein Percentage: (4/30)×100=13.3%

This calculated percentage will help you determine if the flour has enough protein content for building a strong sourdough starter, what hydration levels should you use, and what texture, crumb structure and crust should you expect from your dough. 

And if this sounds like too much hassle…

To save you time and effort, we’ve created a Flour Protein Content Calculator that does all the math for you. Simply enter the serving and protein in grams from the nutrition label on the flour pack, and the calculator will provide the protein percentage for you.

How to Calculate Protein Content When Using a Flour Mix

When blending flours (e.g., bread flour and all-purpose flour), knowing the final protein content might be important for achieving the desired dough characteristics. Use the formula in the example below to work out the final protein content in your flour blend.

Example:

Flour A: 300g bread flour at 12.5% protein

Flour B: 100g all-purpose flour at 9% protein

Final Protein Content=((12.5×300)+(9×100))/400=11.6%

The below Protein Content Calculator For Flour Mix will do the math for you. Simply input the weights and protein percentages of your flours, and the calculator will provide the protein percentage for you.

Let us know if you have questions about protein content and how to calculate it! And leave a comment below to share your feedback.

What’s Next?

If you like our calculators - take a look at the Calculators Section where we have more useful tools for you to help you with the math!

You might be especially interested in the Baker’s Percentage Calculator. With our intuitive design, and instant results, you will be able to easily work out grams or percentages of your sourdough ingredients.

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