There’s sense in which the ritual of boiling bagels is just that: a ritual. As I mentioned yesterday, the practice of briefly boiling, then baking, small breads goes back millennia. For some, notably a bevy of commercial bagel makers off the East coast, boiling is a self-defeating spring-inhibiting anachronism. Yet true bagel lovers know that a bagel isn’t a bagel unless it’s been boiled (poached, really, if you want to get technical about it).
Poaching does at least two things that I know of. First, it cooks the outer layer of the dough, gelatinizing the starch and creating a tough skin. That skin will go on to form a slightly crunchy, chewy crust. It will also restrict the rise of the bagel in the oven like a corset on a plump chorus girl, creating a denser crumb with smaller holes.
The other thing poaching does is of course moisten the outside of the bagel, which, like misting the outside of a baguette, gives enzymes in the skin crucial extra minutes to work before the heat of the oven deactivates them. What are those enzymes doing? Why, breaking starch down into sugars — sugars which eventually caramelize, giving the bagel a nice brown crust. Big chain bagel makers mist their bagels in this way, and the result, at least from a browning standpoint, is comparable to poached bagels. Yet without that restricitive skin they end up light and round like rolls instead of flattish and dense like true bagels should be.