A Little Brittle

In the last experiment/recipe, you learned how to stop crystals from forming by cooling very fast. In this activity, you'll learn another way to prevent crystals. In the kitchen, "table sugar" usually means a molecule called sucrose, which is usually made from sugar cane or sugar beets. Corn syrup, on the other hand, contains other sugar molecules, called glucose and fructose. If you add these types of sugar to the sucrose, the glucose and fructose lead to "mistakes" when crystals try to form, and the result is - no crystals (or at least, not very many)!

This is a recipe for nut brittle, which uses corn syrup mixed with table sugar to keep crystals from forming. The presence of crystals would not change the taste of the candy, but would make it feel gritty in your mouth. Nut brittle is most commonly made with peanuts, but you can also make it with other nuts, if you don't like peanuts or can't eat them.

What you'll need:
1/2 cup light corn syrup
1 cup sugar
1 cup dry-roasted peanuts or other nuts
2 teaspoon butter
1 teaspoon vanilla extract
1 teaspoon baking soda
Salt (if you want)
Microwave oven
Large microwave-safe bowl
Spoon
Baking pan (10" x 10")
Oven mitts

Rub the baking pan with about 1 teaspoon worth of butter and put it aside. Mix the corn syrup and sugar in the bowl and microwave on high for 4 minutes. The sugar should have started to melt, but still be clear. Remove from the oven and stir in the nuts. Be careful - the bowl will be VERY hot. Microwave on high about 3 more minutes or until the mixture turns light brown. Take the bowl out of the microwave again and stir in the other teaspoon of butter and the vanilla extract. Microwave on high again for 1 minute. Remove the bowl again, and stir in the baking soda (what do you see happening?). Quickly pour the mixture into the baking pan and let it cool. When the brittle is safe to handle, slide it out of the pan, and break it into small pieces. If you're going to store it, make sure it's in an airtight container.

This recipe includes another chemical reaction that has nothing to do with sugars or crystals. When you added the baking soda, the brittle got cloudy because thousands of tiny gas bubbles formed. Where did they come from?? When baking soda is heated to 160^oF, it gives off carbon dioxide gas. The sugar/nut mixture is much hotter than this, so the gas is given off very quickly. The bubbles don't change the taste of the nut brittle, but do make the candy lighter and easier to chew.