Candy crush: Swetha Sivakumar on spells cast with sugar and water
What makes pure white sugar so versatile, and so unerringly precise? How does it make candy floss and hard candy and entirely see-through edible glass? Find out, in this week’s Sound Bites.
Put down the wand, pack away the potions. Sugar and water are all it takes to create some magic.
That, and the chef’s undivided attention. People call baking a precise science, but working with sugar requires far more accuracy. The good news is that, unlike with the rather unpredictable mix of milk, flour and eggs, one can always tell exactly what pure white sugar will do.
Calculate the percentage of water to sugar accurately, and you can tell exactly where a batch of boiling syrup is, just from the temperature reading. Plain water boils at 100 degrees Celsius. Adding pure white sugar (which is 99.9% sucrose) raises that boiling point. At 113 degrees Celsius, the boiling liquid is 85% sugar. At 149 degrees Celsius, almost all the water has gone, and the concentrate is close to 100% sugar.
In an aside, this is also why working with sugar solutions requires the utmost care; it can cause severe burns if it touches the skin.
Now here’s a bit of that magic: Controlling the temperature as it rises causes syrup. Controlling it as it cools, causes crystals to form. At this point, depending on how much the chef stirs or pulls, they can control the size of the crystals to make treats that range from the cloud-like cotton candy to the chewy, stringy soan papdi, or prevent the formation of crystals altogether, to make sugar glass.
Sugar glass, also called edible glass, is what you’re really seeing on the screen when a window shatters or one man punches another through a see-through door.
It is made by cooling the syrup so quickly that the sugar does not crystallise at all. Instead, it sets in place as an amorphous structure, very similar to real glass. Since this kind of edible treat is extra-brittle, and completely transparent, it’s a great substitute for the real thing because it poses far less of a risk to actors and stuntmen.
The only problem with sugar glass is that it’s sticky and temperamental at high humidity levels, so filmmakers have replaced it in recent decades with a synthetic thermoplastic resin called “breakaway glass”.
To make sugar glass – and you can certainly try this at home – take sugar, water, an acidic element and a liquid sweetener. Sugar, left to itself, tends to form crystals. Crystallisation occurs best when identical molecules can get close to each other with nothing in-between. When making sugar glass, the addition of acid (in the form of lemon juice, vinegar etc) helps split the disaccharide sugar into its components: unidentical molecules of glucose and fructose. This cleaving impairs crystallisation, the first step in helping sugar become edible glass.
A liquid sweetener (typically corn syrup) is then added to flood the solution with more unidentical molecules. Corn syrup, for instance, contains glucose, maltose and some long chain oligosaccharides; crystals find it even more difficult to form in a mix so diverse. The result, is crystal clear.
In candy where crystals are wanted, there must be plenty of control too. It’s vital to get just the size and type that one wants.
Take cotton candy. Spinning fibers this tiny was almost impossible until the invention of the cotton-candy machine in 1897, by, of all people, an American dentist named William Morrison. But with the machine, even a child can do it. The device spins its airy clouds by first melting the sugar, then forcing the hot, molten sugar through tiny holes. As the sugar solidifies, due to the centrifugal force, its crystals form thin threads that can be whipped around a stick.
In taffy and soan papdi, the sugar solution is cooked to the soft-crack stage (where it resembles lava). At these temperatures, there is some crystal formation. But before the crystals can get large and hard, the gooey, lava-like mix is pulled like a rope and folded back into itself, aerating it and adding new molecules from that air, thereby reducing the size of crystals. The result, as it cools and sets, is an airy, chewy sweet.
While all this is fun, it is of course uniformly bad for our health. The human body does not need white sugar at all. For the chef, the ingredient’s allure holds, as a canvas of infinite artistic possibility. If only there were some way to enjoy that art without swallowing it whole.
(To reach Swetha Sivakumar with questions or feedback, email firstname.lastname@example.org)