Vol. VII · Starches and Sugars Plate 8 of 11caramel, caramelisation, sucrose, colour, bitterness, temperature, time, dry caramel, wet caramelMF

Caramel.

Caramel is not melted sugar. It is sugar breaking apart, and how far it has broken is written in its colour and its bitterness.

Sucrose does not simply melt: above about 160 °C it begins to decompose, losing water and splitting into glucose and fructose fragments that recombine into hundreds of new molecules. Some are brown pigments; some smell of butterscotch, nuts and toffee (diacetyl, furans, maltol); some are acids. As caramelisation proceeds the colour deepens from pale gold to amber to mahogany, the sweetness falls, and bitterness rises — until, past dark brown, it is acrid and burnt.

The reaction speeds up steeply with temperature (V.10), so a caramel at 180 °C darkens several times faster than one at 165 °C, and the last stage passes in seconds. Cooks stop it by taking the pan off the heat and, for a sauce, adding cream or water (carefully — it spits and steams). The workshop follows the colour of a caramel over time at a constant temperature.

Below: the progress of caramelisation (a colour index from pale to burnt) against minutes at three temperatures and yours (course Arrhenius parameters, activation energy 150 kJ/mol), with the bands cooks name.

What you will learn
Workshop
Caramelisation as a first-order reaction (course parameters: 0.04 per minute at 170 °C, activation energy 150 kJ/mol); the index 0–1 runs from clear to black. Bands: pale gold, amber, dark amber, burnt.

Degrees and seconds

In this model a caramel held at 170 °C reaches amber in about 14.9 minutes; at 180 °C in 6.1; at 190 °C in 2.6. Ten degrees roughly halves the time, and near the end the colour moves visibly from one second to the next — which is why caramel is made with full attention, a pale-coloured pan so the colour can be judged, and the cream for the sauce warmed and ready.

Two methods: a dry caramel melts sugar alone in the pan, fast but uneven; a wet caramel dissolves it in water first, boils off the water (VII.6) and then colours more evenly, at the cost of crystallisation risk (VII.7). Butter, cream, salt and vanilla added at the end make caramel sauce; a pinch of baking soda makes honeycomb, its gas puffing the hot glass into foam. Many "caramel" colours in food are not caramelised sucrose at all but Maillard browning of sugars with proteins (VIII.4).

At the stove

Melt 100 g sugar in a light-coloured pan over medium heat without stirring, swirling to even it. Drop a spoonful onto baking paper at pale gold, at amber and at dark amber, and taste each when cool. The sweetness falls and the bitterness rises with the colour.

Caramel colour (E150), made industrially by heating sugars, colours cola, soy sauces, gravies and whisky; it is among the most widely used food colourings in the world.

Terms

Caramelisation
The breakdown of sugar by heat into coloured and aromatic compounds.
Dry caramel
Sugar melted and caramelised without water.
Wet caramel
Sugar dissolved in water, boiled down and then caramelised.
Honeycomb
Caramel foamed with baking soda.
Caramel is sugar breaking down; ten degrees roughly halves the time, and colour tracks bitterness. Stop it in seconds.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
  2. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.