Pretzel Rolls & the pH Scale

This month, I’m teaching students at the after-school program I work at how to bake breads from around the world. The biggest crowd-pleaser so far has been pretzel rolls, which have an interesting history (they were invented in the Middle Ages by European monks) and an unusual baking process.

Before they go in the oven, the rolls are glazed in a baking soda solution. I had students gather around as I poured baking soda into a pot of boiling water. After watching in awe as the baking soda bubbled up, nearly escaping from the pot, the kids took turns dunking their pretzel creations into the foamy liquid. 

This is a great way to introduce young students to the pH scale, or reinforce what older kids are already learning in science class.

How It Works: Glazing dough in an alkaline solution strengthens the browning process that occurs when bread bakes, which is known as the Maillard reaction. The higher the pH, the darker the bread. These days, most recipes call for using baking soda (9 on the pH scale), but traditionally, pretzels were glazed with lye, which has a pH level of 14! Boiling dough also gives it its shiny appearance.

Recipe: There are a number of good pretzel roll recipes on the web, though I’m a fan of this one from Chow.com.

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