What Is Lye?
Baking can be dangerous if you're not paying close attention to what you're doing, but if you're using lye in baking or cooking, the stakes are even higher. You're always at a low-grade risk of burning your fingers or arms on a hot oven or scalding baking sheet, but if you spill lye on yourself, you could get a chemical burn. Lye can also actually kill you, if you accidentally ingest it straight. So given all of the risks of using this dangerous chemical, why do people use lye in cooking? Well, as Brian X. Chen explained in the New York Times, lye makes bagels taste better. It's also used in cuisines around the world, as a tenderizer and a curing agent, and if used properly and with the proper knowledge, it can definitely beef up your homemade bagel game without killing you or your loved ones.
The key to cooking with lye is understanding how it works, though the more you learn about the chemical compound, the harder it might be to convince yourself that using it in your food is a good idea. To this day, when someone mentions lye, I still think about that scene in Fight Club, where Brad Pitt's character is making soap and pours the liquid lye on Ed Norton's character's hand, giving him a chemical burn and making him convulse—not bagels.
And it turns out that, just like in the movies, lye is used to make soap. It can also be used as a hardcore home-cleaning agent, such as Drano, and is sometimes used by contractors to literally dissolve the carcasses of roadkill. Mexican cartel members have also been using it to get rid of victims' bodies. But the most relevant use of lye to my interests is as a baking or cooking ingredient. (This seems like an unnecessary disclaimer, but I feel a responsibility to state here that any lye you're using for cooking must be food-safe. Don't start thinking that you can boil bagels in Drano, OK?)
Lye is simply sodium hydroxide, a chemical compound that is very basic (in the chemical sense because it's an alkalai), and its ability to dissolve natural matter with ease is the most terrifying thing about it. But that's also what makes lye such a powerful cooking and curing agent. Lutefisk, for example, is a Norwegian dish—"a piece of dried, salted cod that has been soaked in a bucket of lye for several days," according to the authors of Advances in Food Science and Nutrition. The lye breaks down the fish, giving it a gelatinous texture and an aggressive scent that some people love. Many others do not.
Lye really gets going when you bake it, though, and that's why one genuinely beloved application of lye is in baking soft pretzels. Dipping a pretzel in a heavily diluted, and very basic, lye mixture before baking turns the dough a distinctive yellow color and helps facilitate the Maillard reaction, which is responsible for creating that distinctive, dark brown crust. The lye breaks down some of the proteins on the outside of the dough and speeds up the whole baking process. And since nothing else really gets as basic as lye, few other compounds are as effective as getting that texture. If you were still worried about accidentally poisoning yourself after baking, know that lye reacts with carbon dioxide from the heat in the oven and forms a carbonate, according to The Kitchn, making the lye safe and the baked goods totally safe to eat (as long as you used a diluted enough lye solution in the first place).
This is the same reason why Chen insists that bagels are best after boiled in lye. Not only does the boiling set the crust, the lye also facilitates that chemical reaction to make the outside crust crusty enough while keeping the inside soft and light.
Not every New York-style bagel is boiled in lye, though, so if you're going to make bagels in the comfort of your own home and don't want to mess around with chemical burns or accidental poisonings, forgo the lye and use baking powder instead. If you are going to dare to use lye in your recipes, make sure to use protection—including goggles, gloves, and an apron. Don't be cavalier. Otherwise, I'll be Jack's complete lack of surprise when you show up with a burn—and no bagel is worth that.
But if you take your time and play it smart, you'll end up with a bagel or a pretzel you won't be able to believe you made yourself.