How donuts are made

A donut floats in hot oil, browns one side, and gets flipped to brown the other.

stations: 6
things upstream: 70
raw sources: 20
steps from the ground: 10

The short version

On an automated line, dough from flour, yeast, sugar and fat is poured into a hopper and pushed through an extruder that forms rings with the hole already in place. The rings ride through a warm, humid proof box, float through oil at around 355 to 360 °F, flip once, and pass under a curtain of glaze.

Weigh and mix

Ingredients are weighed on digital scales and carried by automated machines into the mixer. Many shops start from a prepared mix and add water and yeast at this point.

Goes in
Flour Sugar Baker's yeast Eggs Water Vegetable oil
Extrude the rings

Dough drops into a hopper, and an extruder pushes it out in rings. The machine forms the hole as it shapes the ring, so nothing is punched out. Pressurized air keeps the thickness even.
Rise in the proof box

Trays climb up and down a zig-zag conveyor in a tall case full of heat and humidity, around 51 °C for up to 30 minutes in one description. Yeast turns sugar into gas and the rings puff up. Cake donuts skip this and use baking powder.
Float through hot oil

Rings float on vegetable oil at about 355 to 360 °F while a conveyor carries them along. One side fries first, then a flipper turns them over for the other, roughly 45 seconds a side.

355-360 °F

Goes in
Vegetable oil
Pass under the waterfall

Still on the conveyor, each rack runs through a falling curtain of glaze. A pump lifts the glaze from a reservoir to the top of the waterfall, and whatever misses returns to fall again.

Goes in
Sugar
Cool, top and box

The line goes through a cooling stage, sometimes a refrigerated tunnel. Sprinkles and other toppings go on before the donuts are boxed.

Goes in
Sprinkles Cardboard box

End of the lineDonut

Worth repeating

Hanson Gregory claimed to have invented the ring-shaped doughnut in 1847 aboard a lime-trading ship, punching the hole with a tin pepper box.
The first known printed use of the spelling donut was in a book published in 1900.
Cato the Elder recorded a recipe for a deep-fried dough ball made with cheese, honey and poppy seeds.