(Note: this is not an experiment—because you can eat the results. This is a cooking project that shows how science is part of our everyday lives!)
Caramel is a gooey treat that is part of many kinds of candy and desserts. While the recipes may all be different, they are all based on caramelized sugar (melted sugar). When you heat sugar (sucrose) crystals, the sugar begins to melt. Once it melts it breaks apart into to smaller sugar molecules (glucose and fructose). These smaller sugars undergo complex reactions, which cause the color of the solution to change from clear to the familiar caramel color. In fact, caramel is sometimes used as a food coloring—look for caramel color on food labels.
You can caramelize sugar at home on your stove or in the microwave. Making caramel on the stove can be a little tricky, but the microwave makes it easy. Be very careful—the sugar gets very, very hot. Protect your hands and any surfaces where you might put the caramel.
- 1/2 cup sugar
- 1/4 cup light corn syrup
- 2 cup Pyrex measuring cup (be sure to use Pyrex, or something similar—the sugar gets too hot for regular glass)
- A metal cookie sheet, lined with aluminum foil
1) Mix the corn syrup and the sugar in the Pyrex measuring cup. Make sure all the sugar is moistened.
2) Put the mixture in the microwave. Microwave for one minute and then check the solution. Is it bubbling? Has the color started to change from white to clear to tan? (The exact time this takes will depend on your particular microwave oven.)
3) Continue to microwave for one-minute intervals, checking for bubbling and color changes after each minute. Once the mixture starts to darken, remove it from the microwave and place the measuring cup on a hot plate (or other heat safe spot). The color will continue to deepen, even after you remove the cup from the microwave. BE CAREFUL—the syrup is extremely hot!
4) Let the mixture sit for a few minutes, until the color stops changing. If you would like a darker caramel, you can put the cup back in the microwave for 10-15 seconds. Once the color is to your liking, pour the caramel onto the prepared cookie sheet.
5) Let the caramel cool. Once it is cool, you can break it by banging the caramel and cracking it into bite sized pieces.
6) You can eat the caramel once it is cool. Note: this caramel is hard, like a lollipop. Soft caramels also include other ingredients like butter or cream.
Why do you add corn syrup?
If the sugar happens to turn back into crystals, the caramel will taste gritty, instead of smooth. Mixing in some corn syrup helps to make sure that crystals don’t reform.