Why does sugar turn brown when heated?
Heat can break down and rearrange sugar molecules, creating new substances with brown colors and different flavors. This chemical transformation is caramelization.
- The scientific idea
- Caramelization
- Fields of science
- Chemistry
How it works
The amber layer on a crème caramel is a record of chemical change. Sugar molecules have broken down and rearranged into new substances. Simply dissolving sugar in water would leave its molecules intact; caramelization changes what the mixture contains.
Look closer
One complication hides in the name: a chewy caramel candy made with cream can also owe its color to Maillard reactions between sugar and milk proteins. The food's name does not identify its chemistry. Nor is there one temperature that describes every sugar's behavior: the kind of sugar and the conditions matter. For understanding a dessert, the useful question is which ingredients were heated together.