Caramel

Why

A caramel syrup holds far more dissolved sugar than water could keep in solution when cold, and such a supersaturated solution is unstable: a single undissolved crystal from the side of the pan, or a stir of the spoon, is enough for sugar molecules to start piling onto it in a chain reaction until the syrup seizes into a white, grainy mass. A drop of lemon juice splits some of the ordinary sugar (sucrose) into glucose and fructose, and glucose syrup adds these directly; being different molecules, they don't fit into sucrose crystals and so hold crystallisation back. Only once the water has boiled off and the temperature climbs above roughly 160 °C does the sugar begin to break down and caramelise, producing a golden to amber colour and a wealth of aroma compounds. Between dark amber and burnt, bitter caramel there are only a few degrees and a few seconds – and syrup this hot sticks to skin and burns deep.

How to do it

• Use a clean, heavy-based pan and dissolve the sugar in the water completely before the syrup comes to the boil.
• Once it boils, stop stirring and just swirl the pan now and then; wash crystals off the sides with a brush dipped in water.
• For insurance, add a drop of lemon juice or a spoonful of glucose syrup.
• Take the pan off the heat a shade earlier than you want – the caramel keeps darkening in its own heat.
• Add cream or butter warmed, a little at a time and at arm's length: the caramel foams up violently and releases steam.
• Never taste hot caramel, keep children away from the stove and have a bowl of cold water to hand.

If it goes wrong

Crystallised syrup can be saved: add a little water, dissolve the sugar completely again over low heat and start boiling again, this time with a drop of lemon juice. Burnt, bitter caramel can't be saved – pour it away and take the pan off the heat sooner next time. If you get burnt, cool the area as soon as possible under cool (not ice-cold) running water for at least 20 minutes, don't peel set caramel off the skin, and see a doctor if the burn is larger than a palm, the skin is white or charred, it is on the face or hands, or a child is burnt.