Alkalis speed up browning
Also searched as: lye, pretzel, baking soda browns, alkaline, brown pretzel
In short: In alkaline conditions the runs much faster. That is why pretzels turn deep brown and onions with a pinch of baking soda darken faster.
Like a tailwind on a bike: the route is the same, but you get there much faster.
What happens
The browning reaction depends on the . Acid slows it down; alkalis such as baking soda or lye speed it up a lot. Pretzels are dipped briefly in a lye bath before baking: the surface then browns deeply, shines and gets its typical taste. A pinch of baking soda makes onions brown and soften faster; too much tastes soapy.
Why it matters
Explains the colour of pretzels and lye rolls, and why a hint of baking soda saves time when frying.
Rules of thumb
- For onions, a pinch of baking soda on the tip of a knife, no more.
- Acid such as lemon or wine slows browning, so add it later.
- Real food-grade lye is caustic: gloves, goggles, nothing made of aluminium.
Levers
In practice
Bread
Pretzel: dipped briefly in lye, then baked. At home, baked baking soda gives a milder version.
Vegetables
Onions with baking soda turn golden brown in half the time.
- Harold McGee: On Food and Cooking (2004)