Caramelization is the browning of sugar

Sugar

Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

, 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

Caramel

Caramel is a beige to dark-brown confection made by heating any of a variety of sugars. It is used as a flavoring in puddings and desserts, as a filling in bonbons, and as a topping for ice cream, custard and coffee....

 flavor.

Like the Maillard reaction

Maillard reaction

The Maillard reaction is a form of nonenzymatic browning similar to caramelization. It results from a chemical reaction between an amino acid and a reducing sugar, usually requiring heat....

, caramelization is a type of non-enzymatic browning. However, unlike the Maillard reaction, caramelization is pyrolysis

Pyrolysis

Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...

, as opposed to reaction with amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s.

When caramelization involves the disaccharide sucrose

Sucrose

Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...

, it is broken down into the monosaccharides fructose

Fructose

Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...

 and glucose

Glucose

Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

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

• equilibration
  Chemical equilibrium
  In a chemical reaction, chemical equilibrium is the state in which the concentrations of the reactants and products have not yet changed with time. It occurs only in reversible reactions, and not in irreversible reactions. Usually, this state results when the forward reaction proceeds at the same...
  
   of anomeric and ring forms
• sucrose inversion to fructose and glucose
• condensation reaction
  Condensation reaction
  A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...
  
  s
• intramolecular bonding
• isomerization of aldose
  Aldose
  An aldose is a monosaccharide that contains only one aldehyde group per molecule. The chemical formula takes the form Cnn. The simplest possible aldose is the diose glycolaldehyde, which only contains two carbon atoms....
  
  s to ketose
  Ketose
  A ketose is a sugar containing one ketone group per molecule.With 3 carbon atoms, dihydroxyacetone is the simplest of all ketoses and is the only one having no optical activity. Ketoses can isomerize into an aldose when the carbonyl group is located at the end of the molecule...
  
  s
• dehydration reaction
  Dehydration reaction
  In chemistry and the biological sciences, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule. Dehydration reactions are a subset of elimination reactions...
  
  s
• fragmentation reactions
• unsaturated polymer
  Polymer
  A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
  
   formation.

The process is temperature-dependent.