The Proof Box
The proof box, or proofer, is a tall glass case that houses a doughnut conveyer belt. The conveyer belt carries doughnut trays slowly up and down in a zig-zag motion all the way through the proof box.
The purpose of the proof box is to surround the doughnuts with heat and humidity. Humidity and low heat make the yeast organisms more active without killing them. When the yeast becomes active, it eats sugar and releases carbon dioxide gas as a waste product. The carbon dioxide expands, creating air pockets all through the dough (see How Bread Works for more information).
See the proofer in action!
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In order to heat the doughnuts to just the right temperature, the proof box machine has to keep the heat and humidity at very specific levels for a certain amount of time. If it gets too hot or humid, the machine opens up vents in the side of the proofer to let some air out. Krispy Kreme doesn't publicize the exact proofer settings, as they're part of the secret recipe. The dough spends 15 to 20 minutes in the proof box.
As the conveyer belt carries the dough through the proof box, the yeast transforms the dough from a thin ring to a full size, puffed-up doughnut. When the doughnut has fully expanded, it's ready to be cooked.
Krispy Kreme reports these statistics on its Web site:
- Every day, Krispy Kreme makes about 5 million doughnuts.
- Every year, they make about 2 billion doughnuts.
- Every week, they make enough doughnuts to reach from New York to Los Angeles.
- Every year, they use up two Olympic-sized swimming pools worth of chocolate.
- Every year, they use about 1 million pounds of sprinkles.
- Collectively, Krispy Kreme's stores could make a doughnut stack as high as the Empire State Building (that's 1,454 feet or 443 meters) in only two minutes.