Using All-Purpose Flour vs. Bread Flour in Sourdough Bread

When it comes to making sourdough bread, does it matter if you’re using all-purpose flour or bread flour?

Simple answer: yes.

Longer answer. It depends.

It comes down to the protein content in bread, how much gluten can be developed, and how much hydration it can handle. Not all flours that parade under the name “all-purpose” are equal, nor are all flours that parade under the name “bread flour” equal.

It also depends on what you want out of your bread. Different flours will yield different results, but that doesn’t necessarily make them “bad.”

If any of the terms in this article feel foreign or you’ve just forgotten what they mean, check out this article on Sourdough Terminology, in alphabetical order.

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Protein content in flour

The main difference between flours of different names is their protein content. The higher the protein content, the stronger the flour, and usually the better for making bread. In the US we have basically five different categories of flour, as far as protein content goes:

Cake flour is the most delicate flour, usually with a protein content of 5-9%. It is made with soft red or white wheat of a fine grind.
Pastry flour is another more delicate flour with a lower protein content, 8-10%. This flour will give you flaky and tender pie crusts, cakes, etc. It is made from soft red or white wheat with a fine grind.
All-purpose flour is more middle of the road with a moderate protein content, anywhere from 8-12%. Can be used for the widest range of baked goods while still yielding good results, if not always the most tender crusts or highest rising breads. All-purpose is made from hard red wheat or a blend of hard and soft wheats.
Bread flour has a higher protein content, 11-13% and suitable for breads where you want higher rises and higher hydration levels. It is milled usually from hard spring wheat.
High-protein bread flour is bread flour with the highest protein contents, 13 or 14% or higher, best for pushing the limits for high hydration breads and open crumbs. It is milled from hard spring wheat.

There doesn’t seem to be an industry standard for flours, at least here in the States, as you can see with the percentage range for each kind of flour.

Even when using the same kind of flour from the same brand there can be noticeable discrepancies when baking bread with different bags of flour.

While variabilities exist across some brands, others are just as good at maintaining consistency. A good example of this would be King Arthur. Their protein content is proudly labeled on each bag of flour, tested, and trusted by consumers, myself included.

There is also an overlap with all-purpose and bread flour. Some all-purpose flours have a higher protein content than bread flour. At the end of the day, it’s more important to know what the protein content of the flour you’re using is than if it’s labeled as all-purpose or bread flour.

Another thing to consider is where in the world you are. For example, I’ve heard from some Canadians that their all-purpose flour is consistently around 13% or even higher in protein. That’s better than most bread flours here in the US! Let’s not even get into trying to buy flour in certain other countries, where they sell flour more by variety and grind than labeling it for its purpose. That’s how flour is sold in Italy, and I had a lot to learn about flour when I first moved there! I couldn’t even bake off a simple batch of chocolate chip cookies without first learning about soft and hard wheat and grind 00, etc…and in another language. If you find yourself in a similar situation, I wrote a couple articles on that to decipher the flours in Italy, and honestly, it’s not bad information to know if you’re really going to get into bread making and understanding how flours work beyond labels. This one will walk you down the flours that are sold in Italy, while this one walks you through the kinds of wheat grown.

Which to Use for Making Sourdough?

If you’ve been making sourdough bread and are happy with your results, then it probably doesn’t matter so much which one you’re using.

However, if you’re looking for a higher oven spring, a rounder belly, a stronger dough to hold inclusions, or wanting to play with higher hydration doughs, you should consider trying a flour with a higher protein content.

Loaf made with Bread Flour (L) and Loaf made with AP Flour (R)

The Side by side comparison

For a visual, I made two loaves of sourdough side by side, identical in every way, except for one uses all-purpose flour and the other uses bread flour.

The process went like this:

One loaf used exclusively Kirkland Signature Organic all-purpose flour (Costco brand, 11.5% protein content). The other loaf used King Arthur Bread Flour (12.7% protein content.)
72% hydration, 20% starter, 1.6% salt
All ingredients were mixed well together for each loaf.
30 minute rest, then 4 sets of stretch and folds every 30 minutes.
Bulk ferment lasted a total of 7 hours 20 minutes with dough temperature starting at 75°F / 24°C at the beginning and trending downwards at 73°F / 23°C by the end of stretch and folds.
Pre-shape for 20 minutes, then final shape before placing into fridge for retard overnight.
Next morning, baked loaves in oven preheated to 450°F / 232°C with dutch ovens for 35 minutes with lids on and steam.

As you can see in the photos, the end result immediately gives away that the bread flour loaf got a better oven spring, a bigger and smoother belly.

The AP loaf, while not ugly, is a little lower, a little flatter. If you look at the belly, you can see signs where the dough tore, spreading more sideways than fully upwards. The gluten just couldn’t be built up quite strong enough to get the same rise as the bread flour.

As far as working with the dough, I could see similar tearing happening even from the beginning. While doing stretch and folds, the bread flour dough came together smoothly and beautifully. The AP dough, while still smooth, would show signs of micro tears as I was working with it. It’s possible the Kirkland organic AP would do better with a slightly lower hydration, but these loaves aren’t high hydration by any means, 72%.

The crumb is curiously different, with the bread flour loaf having a few larger bubbles. I liked the evenness of the AP crumb.

As far as these two loaves go in this mini experiment, the bottom line is they were both delicious loaves of homemade bread. It would be up to you to decide if you prefer the more aesthetic, higher rise of the bread flour, or if you put more importance on eating organic flour, for about the same price.