How corn starch is made

Corn is soaked until it ferments slightly, then the starch is washed out of it with water.

stations: 6
things upstream: 2
raw sources: 2
step from the ground: 1

The short version

Starch factories steep whole corn kernels in warm water for 30 to 48 hours until the grain softens and ferments a little. Mills grind the soaked kernels, separate the germ and fiber, and wash starch out of the endosperm. Hydrocyclones and centrifuges then isolate the starch, which is dried to a white powder.

Soak the kernels

Whole corn sits in steeping tanks of warm water for 30 to 48 hours. The soak softens the kernels and ferments them slightly, which loosens the starch from the protein that holds it.

30 to 48 hours

Goes in
Corn Water
Split off the germ

Coarse mills tear the swollen kernels open, and the germ floats off. The germ is the oil-rich part, so it goes on to make corn oil.
Grind the rest finer

The germ and the endosperm are ground separately while still wet. Fine grinding frees the starch granules from the fiber that traps them.
Wash the starch out

Screens catch the fiber while the starch and protein wash through as a milky stream. Hydrocyclones and centrifuges spin the stream so that heavy starch separates from corn gluten and steep liquor.
Dry to a powder

The wet starch cake is dried in hot air until it is a fine white powder. Everything that was separated out, including the fiber, gluten and steep liquor, goes on to make animal feed or other products.
Modify it if needed

Starch headed for specific uses may be chemically or physically modified. Examples include starch that thickens without clumping or that resists breaking down under heat.

End of the lineCorn starch Next it goes into aspirin, vitamin c tablet, corn syrup and 10 more.

Worth repeating

Corn starch was used mostly for stiffening laundry until a method for pure culinary starch was patented in 1854.
Fine starch dust can explode, and the 2015 Formosa Fun Coast fire in Taiwan is believed to have started with overheated corn starch based powder.
Mixed with a little water, corn starch becomes a non-Newtonian fluid that is runny when poured and hard when punched.