Plain Flour vs High Protein Bread Flour: What’s Best for Sourdough Baking?

If you are new to sourdough baking, one of the first points of confusion is flour. Recipes often specify bread flour, strong flour, or high protein flour, but supermarkets also stock plain flour, which looks very similar.

So what is the real difference between conventional plain flour and high protein bread flour, and why does it matter so much for sourdough bread?

At our sourdough bakery, this is one of the most common questions we hear from beginners. The short answer is that flour choice plays a huge role in how your dough behaves, how well it rises, and the final texture of your loaf.

What Is Plain Flour?

Plain flour, sometimes called all purpose flour, is designed to be versatile. In the UK it is commonly used for cakes, biscuits, pastries, sauces, and general cooking.

Plain flour typically has:

 
• A lower protein content, usually around 9 to 10 percent
 
• A softer texture
 
• Less gluten forming potential

This makes it ideal for tender baked goods where you do not want much structure, such as sponge cakes or shortcrust pastry.

What Is High Protein Bread Flour?

High protein bread flour, often labelled as strong white bread flour in the UK, is made specifically for bread baking.

It typically has:

 
• A higher protein content, usually 12.5 to 14 percent
 
• Strong gluten forming potential
 
• The ability to hold its shape during long fermentation

This extra protein is what gives bread dough strength and elasticity.

Why Protein Matters in Sourdough Baking

Protein in flour becomes gluten when mixed with water and worked. Gluten forms a stretchy network that traps gas produced during fermentation.

Sourdough fermentation is slower than commercial yeast baking and lasts much longer. Because of this, the dough needs enough strength to hold onto gas without collapsing.

This is where high protein flour becomes especially important.

What Happens If You Use Plain Flour for Sourdough?

It is possible to make sourdough with plain flour, but beginners often struggle when they try.

Common issues include:

 
• Dough spreading out instead of holding its shape
 
• Weak rise in the oven
 
• A dense or gummy crumb
 
• Loaves that flatten during proving

Plain flour does not have enough protein to support long fermentation, especially when working with wetter sourdough doughs.

Why High Protein Flour Is Better for Sourdough Bread

High protein bread flour gives you a much wider margin for success.

It allows:

 
• Strong gluten development
 
• Better gas retention during fermentation
 
• Improved oven spring
 
• A lighter, more open crumb
 
• Dough that is easier to shape and handle

This is particularly helpful when learning techniques such as stretch and folds, shaping, and cold proving.

Does High Protein Flour Affect Flavour?

Flavour in sourdough mainly comes from fermentation rather than protein level. However, because high protein flour supports longer fermentation without breaking down, it indirectly helps flavour development.

Longer fermentation leads to more complex flavour, better balance between acidity and sweetness, and improved keeping quality.

Which Flour Should Beginners Use?

For anyone starting out with sourdough baking, we recommend using strong white bread flour as your main flour, with wholemeal or rye flour used for feeding your starter.

Once you are confident, you can experiment with blending flours or using lower protein flour in small amounts. For learning and consistency, high protein flour provides the best foundation.

Final Thoughts

Flour choice is one of the most important decisions you make in sourdough baking.

While plain flour has its place in the kitchen, it is not well suited to long fermented sourdough bread. High protein bread flour provides the strength, structure, and reliability that sourdough requires.

If sourdough baking feels unpredictable or frustrating, changing your flour is often the simplest improvement you can make.