Understanding the Method of Bran from Flour: Sifting and Milling Explained

December 2, 2025 •

3 min read

According to agricultural data, the outer layer of a wheat kernel, known as bran, contains over 40% dietary fiber, significantly more than refined white flour. The method of bran from flour is fundamentally a process of particle size separation, a technique employed by bakers and industrial mills alike to create different flour types.

Quick Summary

The method of separating bran from flour primarily uses sieving based on particle size, a process that is adapted for both simple home techniques and complex, multi-stage industrial milling operations.

Key Points

Sieving is the primary method: The most basic way to separate bran from flour is by using a sieve to filter out larger bran particles from finer flour powder.
Particle size is the key factor: This physical separation technique works because bran flakes are larger and coarser than the endosperm particles that become flour.
Industrial milling is multi-staged: Commercial production involves cleaning, tempering (adding moisture), grinding with roller mills, and repeated sifting and purification for maximum separation.
Tempering toughens the bran: In industrial milling, water is added to toughen the bran layer, preventing it from disintegrating during grinding and making it easier to separate.
Bran separation impacts nutrition: Whole wheat flour retains the bran and germ, making it higher in fiber, vitamins, and minerals compared to refined white flour.
The final product's texture is affected: Bran separation results in flours with different characteristics; refined flour is finer and softer, while whole wheat is denser and nuttier.
Separation enhances shelf life: The germ contains oils that can cause spoilage. Removing the germ and bran in refined flour production extends its shelf life significantly.

The Fundamental Principle of Separation: Sieving

At its core, the method of bran from flour is a physical separation process called sieving. This technique exploits the difference in particle size between the larger, coarser bran flakes and the finer, powdery flour (endosperm). A sieve, or sifter, acts as a filter, allowing the smaller flour particles to pass through its mesh while retaining the larger bran particles above.

The Home Kitchen Method

For home bakers or those who grind their own whole grains, the process is straightforward and low-tech:

Grinding: Begin by grinding the whole wheat kernels using a burr grinder, blender, or home mill. This breaks the hard kernels into a mixture of fine flour, bran, and germ. Home-milled flour is known for its rustic texture and robust flavor.
Sifting: Pour the freshly ground grain powder into a fine-mesh sieve or flour sifter. Gently shake or tap the sieve over a bowl or surface. The fine flour will fall through the mesh, while the larger bran particles are left behind.
Collection and Use: The refined flour can be used for baking, while the separated bran can be added to cereals, muffins, or bread for added fiber and nutrients. Some methods suggest a second sift of the remaining bran to extract any last bits of flour.

The Industrial Milling Process: Scale and Refinement

Commercial flour production utilizes a far more complex and automated process known as roller milling to separate bran from flour on a large scale. This method ensures consistent quality and produces different flour grades, from whole wheat to highly refined white flour.

Key Stages of Commercial Milling

Cleaning: The process begins with thoroughly cleaning the wheat kernels to remove all foreign material like stones, dirt, and other seeds.
Tempering: Wheat is conditioned by adding a precise amount of water and allowing it to rest. This toughens the bran coat, preventing it from shattering into tiny, difficult-to-separate pieces, and softens the starchy endosperm for more efficient grinding.
Grinding (Breaking): The tempered grains pass through a series of corrugated steel rollers, or 'break rolls', which rotate at different speeds. This gently cracks the kernels open, scraping off the starchy endosperm from the bran.
Separation (Sifting and Purifying): The resulting mixture of endosperm chunks, bran flakes, and germ is sent to a multi-stage sifting system, typically a large, box-like sifter with a series of cloth or wire screens. The purifier system then uses air currents and vibrations to separate the endosperm particles from the lighter bran.
Reduction and Blending: The endosperm fragments (called middlings) are sent through another set of smooth rollers that progressively grind them into fine flour. These steps of grinding and sifting are repeated multiple times until the maximum amount of flour is extracted. Finally, different streams of flour may be blended to achieve a desired grade or quality.

The Impact of Separation: Nutritional Profile and Baking Properties

The decision to separate bran from flour directly impacts the nutritional composition and handling characteristics of the final product. Refined white flour, stripped of the bran and germ, differs significantly from nutrient-dense whole wheat flour.

Comparison of Refined and Whole Wheat Flour


Feature	Refined White Flour (Endosperm Only)	Whole Wheat Flour (Entire Kernel)
Processing	Bran and germ removed	All parts of the kernel are milled together
Dietary Fiber	Low	High (bran contains over 40% fiber)
Vitamins	Low (some are added back through enrichment)	Higher levels of B-vitamins and Vitamin E
Minerals	Low (iron, zinc, magnesium)	High (iron, zinc, magnesium, potassium)
Nutty Flavor	Milder taste	Robust and nutty
Texture	Fine and soft	Coarser, denser texture
Shelf Life	Longer due to removal of perishable germ	Shorter, as germ's natural oils can go rancid

Conclusion: The Purpose Behind the Process

Whether accomplished with a simple kitchen sieve or a complex series of industrial roller mills and purifiers, the method of bran from flour is all about separation by particle size. This fundamental technique has been adapted over centuries to produce the variety of flours we use today. The choice to separate bran has profound implications for a flour's nutritional content, flavor, and how it behaves in baking. For home bakers, it offers control over the final product's rustic texture, while for commercial producers, it ensures consistent quality and shelf life. Ultimately, understanding this process helps appreciate the journey of a single grain from the field to a finished loaf of bread.

Frequently Asked Questions

The simplest method is sieving. After grinding whole wheat grains, you can use a fine-mesh sieve or a flour sifter to separate the coarse bran flakes from the fine flour powder.

Commercial mills separate bran to produce different types of flour, particularly refined white flour. Removing the bran and germ results in a longer shelf life and a lighter, finer-textured product preferred for certain baked goods.

Tempering is the process of adding moisture to wheat kernels before grinding. This toughens the outer bran layer, making it less likely to shatter into small pieces during milling, which aids in its separation from the starchy endosperm.

In industrial milling, roller mills are used to progressively break down the wheat kernels. The break rolls gently separate the bran and germ from the endosperm, after which the components are further separated by sieving and purification.

Yes, whole wheat flour is generally considered healthier because it retains the nutrient-rich bran and germ. This makes it significantly higher in dietary fiber, vitamins, and minerals compared to refined white flour.

Removing the bran results in a lighter, softer flour with a milder flavor. When bran is included, as in whole wheat flour, the result is a denser texture and a more robust, nutty flavor.

Yes, leftover bran is a nutritious byproduct that can be added to increase the fiber content of various baked goods. It's often used in muffins, bread, and cereals.