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How are cereal grains milled into food products?

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A large red and yellow combine harvester cuts through a golden wheat field, leaving neat rows of harvested grain behind. — Cereal farming Combine harvesting wheat.

Milling is the primary process of grinding cereal grains to make them suitable for cooking and consumption. While methods vary depending on the specific cereal and regional customs, the process generally involves cleaning, conditioning, and mechanical reduction.123

Wheat Milling

Modern wheat milling typically employs a "gradual reduction" process. After cleaning and dampening, the grain passes through a series of grooved steel cylinders (break rolls) that tear the kernel open. The resulting mixture is sieved to separate the endosperm from the bran and germ. The endosperm—often in the form of semolina—is then ground into fine flour using smooth reduction rolls. This cycle of grinding and sieving is repeated to maximize flour recovery, with air purifiers used to remove branny impurities.231

Other Cereals

Rice: Milling often involves hulling, followed by pearling and whitening to remove thin outer coats. Some rice is parboiled—steeped in hot water and steamed—before milling to improve nutritional retention.4
Corn: While dry milling is common in many regions, corn is also frequently processed using wet milling techniques.1

Most milling processes aim to isolate the starchy endosperm, often removing the bran and germ to improve texture and shelf life.13