Lye and Food

Hear the word "lye" and you probably think of commercial drain opener. A powerful alkali, lye (typically sodium hydroxide or potassium hydroxide) is often used in heavy cleaning and soap making, and it can be highly corrosive. But alkalies, like lye, are also widely used in the food world, a common one being baking soda (a mild alkali, the soda reacts with acidic ingredients to help leaven baked goods). Commercially, corn is often treated with alkali ("nixtamalization") to make hominy. Cocoa powder can be treated with alkali (Dutch process) to neutralize the acid, giving the powder a milder flavor and richer color. Lye is also used in the curing of olives, the canning of mandarin oranges, and in the preparation of Chinese "century eggs" and Nordic lutefisk. My favorite use is making pretzels. With pretzels, the dough is dipped in a very mild solution of lye; most sources I found call for a 3% solution (about 2 TB/Qt of water). When the pretzel is dipped in the solution, the lye immediately begins to react with the surface of the dough, yellowing it. As it bakes, the color intensifies and turns a deep, glossy brown, the pretzel taking on a crisp, chewy texture. The alkali is neutralized in the process, making the pretzel safe to eat. The alkaline environment also promotes the Maillard reaction, the chemical process that leads to browning of such foods. The Maillard process is integral to all bread baking — it shapes the way the crust forms and tastes. In the case of the pretzel, the Maillard reaction is responsible for the deep brown crust, crunchy arms and distinctive taste. At its most basic, the Maillard process is a heat-activated reaction between small sugars and amino acids. Dipping dough in lye alters the ratio between sugar and protein, because lye breaks proteins present in the dough into smaller bits. Those are the small amino acids that then combine with sugars in the dip to create the flavor compounds at the pretzel's crust. The dipping process is an important part of pretzel baking. If you don't put a browning agent on the product, the pretzel is white. If you let it go into the oven white, it'll come out of the oven white. And then you just have a chewy bread chunk.