Peanut brittle is characterized by a light texture with many bubbles. Brittle should snap apart by hand and break easily when you bite it. This is what separates a brittle from another sugar syrup candy, like toffee. Baking soda isn't in every peanut brittle recipe, but for many candy makers, foaming brittle recipes with baking soda provide a near-guarantee of perfect peanut brittle.
Peanut brittle has a short list of ingredients, usually including sugar, raw peanuts, corn syrup, butter and vanilla. The sugar and corn syrup are cooked to the hard crack stage, between 305 and 310 degrees Fahrenheit. This produces the rich, caramel flavor associated with brittle. You'll add raw peanuts as the brittle cooks, then stir in butter, vanilla and baking soda dissolved in a small amount of water once the brittle is cooked.
Baking soda provides the brittle texture in your peanut brittle. When baking soda interacts with the sugar acids present in your brittle, it creates carbon dioxide. Carbon dioxide produces the airy, lacy texture you see when you snap apart a piece of peanut brittle. While you can produce brittle by slow-cooking sugar in a cast iron pan, adding baking soda is the most effective way to achieve the desired texture.
Adding the Baking Soda
If you've never made peanut brittle, you may find the reaction between the baking soda and melted sugar mixture to be quite surprising. As soon as you add the baking soda, the peanut brittle will begin to foam, often reaching two to three times its original volume. Prepare brittle in a relatively large saucepan and protect your hands with potholders to avoid potential burns from the melted sugar mixture.
Pouring the Brittle
You should pour your brittle immediately after you add the baking soda, while the mixture is still foaming. Working carefully, transfer the brittle into a greased or parchment-lined and greased baking sheet. Pour 1/8-inch to 1/4-inch thick for the best texture. Break into pieces when it cools.