Have you ever thought about the difference between all purpose flour AND bread flour? Or maybe you've noticed the big number on the front of bags of King Arthur flour (11.7%, in the case of all-purpose flour) and wondered what exactly it refers to. The answer to both questions is the same: the percentage of protein, one of the most important variables in flour. But what exactly does this mean and why does it matter?
Please note: The protein percentages listed for certain types of flour in this post are what we here at King Arthur guarantee. Other brands often have a more variable protein percentage, so results may vary.
What is the protein in flour?
When we talk about protein in flour, we're talking about two very specific types of protein found in wheat: glutenin and gliadin.
Most important, these two proteins are the building blocks of gluten. When water (or a liquid that includes water, such as milk) is added to these two proteins, they bind together, forming gluten. Gliadin gives the dough extensibility (meaning the dough can be stretched), while glutenin contributes elasticity (so it can be snapped like a rubber band).
After all, if the proteins in flour form gluten, then the more protein in the flour – that is, the higher its protein content – the more gluten-forming potential the flour has. Another way to think about it: the higher the protein content, the “stronger” the flour.
Photography by Mark Weinberg; food styling by Liz Neily
Why protein percentage—and gluten-forming potential—matters
Let's cover a brief overview of gluten's role in baking. When liquid is added to glutenin and gliadin, they begin to form bonds that bind together, developing gluten strands.
As you mix and cook doughs and batters, you encourage the gluten to develop further. This is because this movement and agitation encourages the gluten strands to bond and form a network, making them even stronger.
This adhesive mesh is capable of trapping gas bubbles; the firmer it is, the more gas it can hold, leading to more air in the baked goods and thus a higher rise. At the same time, those cross-linked strands become longer and stronger as the gluten develops, leading to more chewiness and consistency in the final product.
This can be good: You want a strong gluten network bread dough to capture gases produced during fermentation. It can also be bad: You don't want a chewy, stretchy gluten network when making a soft, soft cake.
This is why the amount of gluten-forming potential in your flour, and therefore its protein percentage, matters.
Choose the right flour – and the right protein content – for your baking
Let's examine three main types of flour and how their protein content corresponds to their intended use for baking.
Cake flour: With a protein percentage of 10%, this is considered a low protein flour. It has less gluten-forming potential; when you mix dough made with cake flour instead of all-purpose, there is less protein and as a result, the dough is likely to develop less gluten, resulting in softer baked goods.
Bread flour: With a protein percentage of 12.7%, this is considered a high protein flour. It has more gluten-forming potential; when you mix dough made with bread flour rather than all-purpose flour, there is more protein and as a result, the dough is likely to develop more gluten.
All purpose flour: With a protein percentage of 11.7%, this flour sits comfortably in the middle – enough protein to develop gluten in bread dough, but not so much that it can't also be used to make soft cakes, cookies, biscuits and more.
There are many other flours, all with different protein percentages suitable for specific types of baking. there are high gluten flourFor example, with a large protein content of 14.2% that makes it suitable artisan bread or bagels; on the opposite side of the spectrum, pastry flour It has only 8% protein content, so it is great for baking such as cookies, biscuits and pie crust.
Photography by Rick Holbrook; food styling by Kaitlin Wayne
And finally, a note about whole wheat flour. The total protein content ofwhole wheat flour it's 13.2%, so you might think that, because of its high protein content, it would automatically be great for making bread. And it is, but with some caveats.
Because whole wheat flour contains all parts of the wheat grain, including the bran and germ, the structure of the gluten is affected. This is because the bran has sharp edges when ground, which cut some of the gluten fibers and interfere with their structure. So bread recipes (and other baked goods) with whole wheat flour usually require specific steps to avoid this: they will include a long resting time to allow the wheat bran to soften, or require some kind of second flour to get the taste and nutrition of whole wheat flour, but the benefits of gluten from another flour.
Photography by Rick Holbrook; food styling by Kaitlin Wayne
Why it matters what brand of flour you buy
Unfortunately, some flour brands allow for large fluctuations in their protein content, so each time you use a new bag of flour, you'll get slightly different results. King Arthur flour,however, it is milled to the strictest specifications in the industry. We guarantee that the protein percentage printed on the front of the bag will always match the flour inside.
Baking with flour that has a uniform protein content will give you the best and most consistent results at home, so you won't waste time or ingredients – just lots of delicious baked goods.
Cover photo by Danielle Sykes; food styling by Liz Neily.
