What is gluten?
Gluten is a group of proteins found in grains like wheat, barley, and rye. The two main proteins that make up gluten are glutenin and gliadin. When flour and water are mixed together, these proteins link together and form elastic strands that give bread its chewy texture. People with celiac disease or non-celiac gluten sensitivity cannot tolerate gluten and experience negative health effects when they eat it.
What is a wheat berry?
A wheat berry is a whole, unprocessed kernel of wheat. It contains the bran, germ, and endosperm. The endosperm is the largest part of the wheat berry and is the source of white flour. It contains most of the grain’s protein, including gluten. The bran is the hard outer layer that contains important fiber, B vitamins, and minerals. The germ is the nutrient-dense core that contains healthy fats, antioxidants, and more B vitamins.
When wheat is processed into refined white flour, the bran and germ are removed, leaving just the endosperm. This results in a product that has a finer texture but has lost much of the grain’s nutritional value. Wheat berries, in contrast, are considered a whole grain because all three nutrient-rich parts are left intact.
Gluten formation in the wheat berry
Gluten begins forming during the growing and harvesting process…
As the wheat plant matures, glutenin and gliadin proteins naturally occur and bind together in the endosperm of the wheat berry. The plants use these elastic proteins to provide structure and protection for the developing kernel.
When the wheat is harvested, enzymes are still active and continue linking the gluten proteins together. The wheat berries are then dried and further enzyme activity is halted. Up to this point, the gluten remains mostly undisturbed in the endosperm.
It isn’t until the grains are milled into flour and mixed with water that the gluten networks fully develop. The moisture allows the proteins to unfold and connect with each other, forming long chains that create structure in baked goods.
Gluten content in different parts of the wheat berry
Because gluten is found mainly in the endosperm, the distribution of gluten in a wheat berry isn’t even. The highest concentrations are found in the very center of the endosperm. Moving outward, the level declines gradually. The germ contains small amounts of gluten, while the bran has no gluten at all.
One study analyzed the gluten content in different anatomical fractions of wheat kernels using two varieties of wheat. The results were as follows:
| Wheat Kernel Fraction | Gluten Content |
|---|---|
| Whole kernel | 16.9-18.4% |
| Bran | 0.0% |
| Germ | 3.1-3.8% |
| Endosperm | 46.8-55.2% |
| Inner endosperm | 59.8-65.0% |
| Outer endosperm | 20.2-27.9% |
This shows that while the whole wheat berry contains a moderate amount of gluten, the protein is highly concentrated in the starchy endosperm fraction. The inner endosperm is particularly rich in gluten.
Changes during wheat processing
The amount and distribution of gluten in wheat kernels gets altered when they are processed into finished products:
Cracked wheat
Cracked wheat is made by crushing whole wheat berries into smaller, coarse pieces. This process damages some of the endosperm and liberates gluten stuck in that fraction. However, most of the gluten remains concentrated in the starchy interior of the cracked pieces.
Bulgur wheat
With bulgur wheat, whole grains are parboiled, dried, and broken into particles. The starch gelatinizes during the parboiling step, freeing up some gluten. But like cracked wheat, bulgur still maintains much of its original gluten distribution.
Whole wheat flour
To make whole wheat flour, wheat berries are ground into a fine powder. This extensive mechanical treatment releases glutenLocked inside the endosperm so that it becomes dispersed uniformly throughout the flour.
White flour
When making white flour, the wheat kernel is separated and only the starchy endosperm is ground. Bran particles are removed. As a result, white flour contains less overall gluten than whole wheat flour, but the gluten it does contain is more concentrated since endosperm is the main gluten-containing fraction.
Sprouted wheat
Sprouting wheat berries activates enzymes that start breaking down gluten. The gluten networks degrade further as the sprout continues growing. By the time sprouted wheat is dried and milled into flour, it retains little gluten.
Effects on gluten development
Given the differences in gluten content and distribution, flours milled from various types of wheat kernels will perform differently in baking applications:
Whole wheat vs white flour
Whole wheat doughs are stronger and less extensible than white flour doughs due to higher overall gluten content. But weaker gluten development during mixing can also occur because the bran particles impair gluten network formation.
Sprouted vs regular whole wheat
With minimal intact gluten remaining, sprouted wheat flours cannot form an elastic, stretchy dough. Baked goods will be denser and shorter in texture as a result.
Older vs newer crops
Newly harvested wheat kernels produce flours with stronger gluten than kernels stored for longer periods. During storage, enzymes slowly degrade proteins.
Steps for activating gluten
While gluten exists in a mostly inactive state in intact wheat berries, bakers use various techniques to develop those proteins during wheat processing and dough preparation:
Milling
The physical grinding action of milling wheat berries into flour ruptures starch granules and frees up gluten stuck in the endosperm.
Mixing
Vigorously mixing flour and water allows gluten proteins to fully hydrate and link together as strands.
Kneading
Kneading stretches and aligns the gluten strands to form an organized network that gives dough elasticity and strength.
Fermenting
Enzymes produced by yeast break down large gluten proteins into smaller subunits that can link together better.
Resting
Allowing dough to rest permits gluten strands to relax and realign. This reduces resistance and makes dough easier to shape.
Conclusion
Within a wheat berry, gluten is most heavily concentrated in the starchy endosperm fraction. The proteins remain largely inactive and bound together until the kernel is processed or milled into flour. Wheat processing methods, like sprouting and removal of bran, alter the total gluten levels. Proper dough mixing and fermentation serves to fully activate and develop the gluten network. Understanding how gluten occurs in the wheat berry and how processing changes it helps bakers handle flours appropriately for optimal baked good quality.
