Caramelisation

Caramelisation is a group of pyrolytic reactions in which heat breaks down carbohydrates alone; unlike the Maillard reaction, no amino acids take part. It produces a brown colour and nutty to burnt aromas. It speeds up with temperature, but bitter compounds increase too; it is slowest around neutral pH and accelerates in strongly acidic and alkaline conditions.

The caramelisation temperature varies with the sugar: a 2025 review gives 160 °C for sucrose, glucose and galactose and 180 °C for maltose, and less for fructose. It is not a fixed point – work from the University of Illinois showed sucrose decomposing significantly below its reported melting temperature, only more slowly. The word caramel entered French in 1680 from Spanish caramelo, itself borrowed from Portuguese, probably from Late Latin calamellus, a diminutive of calamus – reed.