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Salty, nutty and irresistibly sweet, caramel can be made in minutes from just a small mound of plain old sugar. The perfect accompaniment to cakes and desserts, caramel is a gourmand’s go-to, and we have a jar of it in my house at all times. Working with sugar can be off-putting, however, because it is so easy to burn it (or yourself) and it can also form grainy crystals rather than smooth, glossy sauce.

So this month, I turned to the professionals for advice, going to the University of Leicester in the UK to visit the newly opened . This lab-cum-bakery is run by chemical biologist and Great British Bake Off finalist Josh Smalley, who is using his love of baking to enthuse people about chemistry. He shared his recipe for the perfect caramel sauce.

Wet caramel, which we are making, first involves dissolving the sugar in water. Combine the sugar and water in a small, heavy-bottomed saucepan, and place over a medium heat. Many recipes suggest you keep stirring the solution, but Smalley insists you give it a swirl to mix the water and sugar then leave well alone. Messing with it can cause the sugar to crystallise, which is where things will quickly start to go wrong. Instead, stand back until the liquid starts to bubble.

A dose of sugar chemistry explains what happens next. Generic sugar you use for baking is the disaccharide sucrose, and when this is heated to just over 180°C (360°F) it will break down into its constituent monosaccharides, fructose and glucose. After this happens, various polymerisation reactions will kick in, where these two simple sugars join together into longer, so-called conjugated molecules, which have alternating single and double bonds. These molecules, confusingly called caramelans, caramelens and caramelins, absorb light – which explains why at this point you are going to see the colour emerge in your bubbling caramel solution.

Now it is time for flavour. As you continue to heat, condensation reactions begin to take place and these molecules lose water and become smaller, producing aroma compounds. Each of these has different flavours associated with them. Some are fruity, says Smalley, others nutty or buttery. Collectively, they produce the delicious rich flavour of caramel.

Your mixture is looking brown and bubbly and smelling terrific, but it is literally crunch time because in mere seconds your caramel could burn: so take it off the heat. The simplest way to stop your caramel from heating further is to add some cold ingredients. Whisk in the butter and cream to create a rich caramel sauce, and add a pinch of sea salt if you like it. You can use your caramel to decorate your other bakes – in Smalley’s case a swiss roll, pictured. Store the leftovers in a tightly sealed jar and refrigerate.

See Catherine baking with Josh Smalley at

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