Caramelization

The brown colors are produced by three groups of polymers: caramelans (C24H36O18), caramelens (C36H50O25), and caramelins (C125H188O80).

As the process occurs, volatile chemicals such as diacetyl (known for its intense butter-like taste) are released, producing the characteristic caramel flavor.

[1] Like the Maillard reaction, caramelization is a type of non-enzymatic browning.

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

Specific sugars each have their own point at which the reactions begin to proceed readily.

Mirepoix (carrots, onions, and celery) being caramelized
A partially caramelized lump of sugar