How are doughnuts filled? I thought they were just injected in but that would compress the dough.

The custard jam etc does not appear to be cooked so I assume it is filled after the cooking process.

But the filling does not share space with the dough. (It is in place of rather than being mixed together).

The dough does not seem to be compressed around where the filling is added.

There are no joining marks where the dough could have been removed and replaced with the filling.

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    I saw a TV show years ago, where they showed the guy pushing donuts onto nozzles (two, as he was doing a donut in each hand), and from what I recall, he wiggled the donuts around a little bit as he was working ... I would assume to make a pocket inside first. – Joe Mar 16 '16 at 16:42
  • The doughnuts are pretty open-structure, right? Maybe it's just how the dough works... gets a huge open cavity in the middle due to the frying/leavening process? – Catija Mar 16 '16 at 17:01
  • @Catija I don't think so, if that were the answer wouldn't an unfilled doughnut have also have a hole? – PStag Mar 16 '16 at 20:11
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    Unfilled doughnuts usually do have holes... through the center... – Catija Mar 16 '16 at 20:35

Donut dough is extremely fluffy, it's mostly air. The filling takes up a very small volume in the donut. The dough does get squished a bit, but that doesn't look all that different from non-squished dough.

If you don't believe me, take an unfilled donut, or a roll of fluffier bread, tear out a piece so you can see the inside, then squish the whole roll/donut between your fingers until it's 1-2 cm less tall than without the pressure. That's what compressed yeast dough looks like.

The baked donuts are simply injected with the already prepared filling from a nozzle, there are no secrets to it.

  • Would this not tear the lattice around the centre and crack the glaze? – PStag Mar 16 '16 at 19:09
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    @PStag The glaze would normally go on after the filling... so, no. – Catija Mar 16 '16 at 19:39
  • And as for tearing, of course you're tearing a hole into it to get to the middle - you can see the hole, probably with some filling oozing out, in the donut. I don't think forcing in the filling causes tearing, though. It's not an insane amount of pressure, just like poking gently at it with a couple fingers. The donut can easily stretch/compress enough to hold it. – Cascabel Mar 16 '16 at 19:41
  • @Jefromi Pressure from filling would be different to pressure from a finger, You would be filling a few individual segments of the lattice with filling rather than an external pressure. It would mean that each part of the lattice is being stretched away from each other. Like a spiders web will hold its structure when the edges it are attached to are moved in but the same pressure from inside a segment will not allow movement. – PStag Mar 16 '16 at 20:09
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    @PStag I don't really understand the argument here. You can get jelly donuts with that telltale hole. You know that the filling was injected. You know that tore a hole into it, including some amount of tearing in the center. You're not just filling a few tiny little bubbles inside the donut, you're filling a large region along the part you tore into, and it can stretch out all along that. Sure, maybe forcing in the filling causes a little additional tearing, but still most of it was done by pushing in a nozzle. And... if there is tearing, so what? This still seems like an answer. – Cascabel Mar 16 '16 at 20:16

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