Caramelization (British English: caramelisation) is the browning of sugar, a process used extensively in cooking for the resulting nutty flavor and brown color. As the process occurs, volatile chemicals are released, producing the characteristic caramel flavor.

Like the Maillard reaction, caramelization is a type of non-enzymatic browning. However, unlike the Maillard reaction, caramelization is pyrolysis, as opposed to reaction with amino acids.

When caramelization involves the disaccharide sucrose, it is broken down into the monosaccharides fructose and glucose.

Caramelization is a complex, poorly understood process that produces hundreds of chemical products, and includes the following types of reaction:

The process is temperature-dependent. Specific sugars each have their own point at which the reactions begin to proceed readily.

The caramelization reactions are also sensitive to the chemical environment. By controlling the level of acidity (pH), the reaction rate (or the temperature at which the reaction occurs readily) can be altered. The rate of caramelization is generally lowest at near-neutral acidity (pH around 7), and accelerated under both acidic (especially pH below 3) and basic (especially pH above 9) conditions.