I understand the surface area-to-volume benefits for reducing the fry time of items like doughnuts, and I suppose there’s a related benefit for bagels during the boiling phase. But isn’t the point of boiling bagel dough to affect the surface finish? They’re subsequently baked - maybe there’s also a benefit there, though certainly not a very significant one.
If the torus provides enough of a benefit to warrant the extra cost of this relatively difficult-to-form object, why aren’t more baked items in this shape?
I’m not sure they’re all that difficult to form: you roll the dough and then connect the two ends. Easier than pretzels and those were made by hand originally, too.
I remember reading that the centers of doughnuts and bagels wouldn’t cook properly if they had solid centers. Leaving a hole made for a uniform thickness that allowed for equal doneness all the way through.
Here’s something close to the recipe I use: Basic Bagel Recipes. They make the hole in a blob of dough with their thumb. I use the snake and water glue method you mentioned.
I buy the doneness explanation for doughnuts because they’re fried, and the high heat at the surface won’t go deep quickly enough to avoid overcooking the crust. Still, there are plenty of oblate spheroid doughnuts that cook just fine.
And with bread the situation is different. Baking allows the heat to penetrate the volume before overly toasting the crust - obviously most bread loaves cook through just fine.
And if you look at the bakery equipment used to make bagels, there’s a lot more machinery required than for buns or rolls.
Good point about pretzels, however. It suggests that part of the point of a bagel is mouth feel of high surface-to-volume ratio. That starts to make sense.
Mangetout mentioned the mechanical benefits. Wikipedia describes one “origination” story about needing to skewer bread rounds for easier handling, though that explanation was talking about handling the finished product. Interesting idea about the hook extractor, though.