Caramelization
Caramelization is what happens when sugar is heated until its molecules break apart and recombine into hundreds of new compounds, turning it brown and giving it a rich, nutty, slightly bitter flavour. Unlike the Maillard reaction, it needs no protein, only sugar and heat.
How it works
As sugar heats past its melting point, its molecules lose water and fragment. The pieces recombine into three main groups:
- Aroma compounds such as diacetyl (buttery) and furans (nutty, toasty).
- Acids that add a gentle sourness.
- Brown polymers (caramelans, caramelens and caramelins) that give colour and body.
The longer and hotter you go, the darker, less sweet and more bitter the caramel becomes.
Caramelization temperatures
Different sugars start at different points:
| Sugar | Approximate start |
|---|---|
| Fructose | 110 °C / 230 °F |
| Glucose | 160 °C / 320 °F |
| Sucrose (table sugar) | 160 °C / 320 °F |
| Maltose | 180 °C / 355 °F |
For table sugar, a light amber caramel sits around 170 °C / 340 °F and a dark caramel near 180–185 °C / 355–365 °F. Past about 190 °C / 375 °F it turns acrid.
Wet vs dry caramel
- Dry caramel: sugar heated alone. Faster, but browns unevenly and burns easily.
- Wet caramel: sugar dissolved in water first, roughly 60 ml (¼ cup) water per 200 g (1 cup) sugar. Slower and more even, but prone to crystallizing if stirred or splashed.
A teaspoon of lemon juice or corn syrup helps keep wet caramel smooth by breaking some sucrose into glucose and fructose, which interfere with crystal formation.
Caramelization vs Maillard browning
They look alike, but:
- Caramelization: sugar only, higher heat, sweet-bitter-nutty.
- Maillard: sugar plus amino acids, lower heat, savoury-roasty-meaty.
Roasted carrots, toast, onions and cookies get both at once, which is why their flavour is so complex.
Common mistakes
- Stirring a wet caramel, which seeds crystals.
- Using a dark pan, so you can't judge colour.
- Adding cold cream all at once, which seizes and splatters. Warm it first and pour slowly.
Questions
At what temperature does sugar caramelize?
Sucrose (table sugar) begins to caramelize around 160 °C / 320 °F and turns deep amber near 180 °C / 355 °F. Fructose caramelizes lower, around 110 °C / 230 °F.
Are caramelized onions really caramelized?
Partly. Onions brown through both caramelization of their natural sugars and the Maillard reaction between those sugars and the onion's amino acids.
Why did my caramel turn grainy?
Sugar crystals reformed, usually from stirring, undissolved crystals on the pan wall, or impurities. A little acid, corn syrup or a lid to steam the sides clean helps prevent it.
How do I stop caramel from burning?
Use a light-coloured heavy pan so you can see the colour, and take it off the heat a shade lighter than you want, since residual heat keeps it darkening.