What Does Milling Remove?

January 6, 2026 •

3 min read

The practice of milling grains has existed since the Neolithic period, marking a significant step in human food processing. Today, this ancient technique has evolved into a highly mechanized process designed to remove specific components from grains, wood, and metal to achieve a desired end product.

Quick Summary

The milling process removes foreign impurities, inedible husks, and nutritious layers like bran and germ from grains. It yields refined flour with a longer shelf life and finer texture while also stripping away key nutrients.

Key Points

Grains: Milling removes the inedible husk, the nutrient-dense bran, and the oily germ from grains to create refined flour and extend shelf life.
Nutrients: The removal of the bran and germ results in the loss of significant amounts of fiber, B vitamins, minerals (iron, zinc), and antioxidants.
Impurities: An initial cleaning stage in milling eliminates foreign materials such as stones, dust, and other seeds to ensure a pure end product.
Texture: By removing the rough outer layers, milling produces a finer texture, which is desirable for many baked goods like white bread and pastries.
Material Shaping: In manufacturing, milling uses rotary cutters to remove material from workpieces of metal, plastic, or wood to create precise components.
Road Repair: Asphalt milling is a process that removes damaged road surfaces, allowing for new layers to be applied, and enables the recycling of old material.

What Milling Removes from Grains

For cereal grains like wheat, rice, and corn, the milling process is a systematic series of steps that meticulously separates the kernel's different parts. The objective varies depending on the desired outcome, whether it's whole-grain flour or a highly refined product. At each stage, specific materials are removed.

Impurities

Before any actual grinding begins, the grain must be thoroughly cleaned to remove foreign materials that are collected during harvest, storage, and transport. This cleaning stage is crucial to prevent contamination and damage to machinery. Materials removed include:

Stones and soil
Weed seeds
Chaff and straw
Other cereal grains
Dust
Metallic objects (using magnetic separators)

The Husk or Hull

Following cleaning, the initial milling step involves removing the tough, inedible outer layer, known as the husk or hull. In rice milling, for instance, this process is called dehulling and results in brown rice. This layer serves as a protective barrier for the grain and is removed mechanically, often using rubber-roller technology for efficiency.

The Bran and Germ

This is the most significant removal in the process of creating refined flour, such as white flour or white rice. The bran is the hard, outer layer of the grain kernel, and the germ is the embryo of the kernel.

Bran Removal: The bran is fibrous and can give baked goods a coarser texture. It is removed in stages through grinding and sifting.
Germ Removal: The germ contains most of the grain's oil content, which can cause the flour to go rancid more quickly. Removing the germ is essential for creating products with a longer shelf life, though it eliminates a source of fat and nutrients.

Loss of Nutrients

The removal of the bran and germ has a direct and significant impact on the nutritional value of the final product. While the endosperm (the starchy part) remains, it lacks many of the beneficial components found in the outer layers.

Key nutrients lost during milling include:

Dietary fiber
B vitamins (Thiamin, Riboflavin, Niacin, Folic acid)
Minerals (Iron, Zinc, Magnesium, Phosphorus)
Antioxidants

To counteract these losses, many refined grain products are enriched, meaning some B vitamins and iron are added back in, though fiber is typically not replaced.

Milling in Other Industries

While grain processing is the most common association, milling is a broad term for using rotary cutters to shape or remove material from a workpiece in many other fields.

Manufacturing

In manufacturing, milling is a machining process that uses a multi-point rotary cutting tool to remove material from a solid workpiece. This can involve shaping metal, plastic, or wood into specific components for various industries, such as automotive and aerospace. CNC (Computer Numerical Control) milling is used for high-precision work.

Road Maintenance

Milling is also a key process in civil engineering and road maintenance. Asphalt milling involves removing the damaged top layer of a road surface. This process prepares the surface for a fresh layer of asphalt, while the milled material can be recycled, making it economical and environmentally friendly.

Comparison: Whole Grain vs. Milled (Refined) Grain


Feature	Whole Grain Flour	Milled (Refined) Flour
Components Retained	Endosperm, Bran, and Germ	Only Endosperm (Bran and Germ Removed)
Fiber Content	High	Low (fiber is primarily in the bran)
Nutrient Density	High (rich in B vitamins, minerals, and antioxidants)	Low (nutrients mostly lost, though some are added back via enrichment)
Shelf Life	Shorter (due to fat in germ that can go rancid)	Longer (fatty germ removed, preservatives sometimes added)
Texture	Coarser, denser	Finer, lighter
Appearance	Darker (due to bran)	Lighter or white

Conclusion

Milling, in its various forms, fundamentally involves the removal of material to achieve a desired quality, texture, or shape. In food processing, this means stripping away the husk, bran, and germ from grains to create refined flour products with longer shelf lives and finer textures. This removal, however, comes at a nutritional cost, as vital fiber, vitamins, and minerals are discarded. Outside of food, industrial milling uses cutting tools to shape solid workpieces, while road crews use it to remove damaged asphalt layers. Ultimately, what milling removes is determined by the specific purpose, with the trade-offs in nutrition, shelf life, or material properties managed to produce the final product. Choosing between a whole-grain product and a refined one, for example, is a direct choice based on what the milling process has removed. For further reading, Harvard T.H. Chan School of Public Health offers more insight into the differences between whole and refined grains.

Frequently Asked Questions

The bran is removed for both practical and aesthetic reasons. It is removed to produce a finer texture and a whiter color in flour, and also because its fibrous nature can interfere with the gluten structure, making it more challenging to achieve a good rise in baked goods.

The germ is removed because it contains most of the fat in the grain. This fat can cause the flour to go rancid over time, so its removal dramatically increases the shelf life of the final product.

Yes, in many regions, refined flour is enriched by adding back certain B vitamins (thiamin, niacin, riboflavin, folic acid) and iron that were lost during milling. However, fiber is not typically replaced.

Whole grain milling grinds the entire grain kernel—bran, germ, and endosperm—together. Refined grain milling first separates and removes the bran and germ, grinding only the endosperm into a fine flour.

In rice milling, the process first removes the inedible outer husk to create brown rice. Further milling, known as polishing, then removes the bran layer and germ to produce white rice.

Yes, regardless of the industry, milling is fundamentally a process of material removal using rotary cutting or grinding tools. This applies whether it's separating grain components, shaping a piece of metal, or removing old pavement.

Grains like wheat are tempered by adding moisture and allowing them to rest. This toughens the bran and softens the endosperm, which makes it easier to separate the layers and reduces breakage during the milling process.