What actually happens when you make fondant? These scientists understood

Delicious and special, a delight on the tongue. Fondant makes the hearts of many people beat faster. Also physicists, because they have discovered that there is still much to learn about the exact formation of flux.

Although it’s hard work, it still looks pretty simple on a kitchen teepee. After all, it comes down to dissolving as much sugar as possible in hot water and then kneading it while it cools. But scientists are not only famous for making hard things easy, but also for making difficult things easy. So what exactly happens at the molecular level when such fondant is kneaded? Or, more scientifically speaking, when supersaturated sucrose water is stirred.

To find out, Hannah Hartge and her colleagues at the Max Planck Institute got to work with an industrial fondant machine. You can tune and monitor these devices very precisely, and if you also put the sugar water under the microscope at different stages, you will learn a lot. They used the most basic fondant you could imagine, made of water and granulated sugar, so their view of the process wasn’t clouded by all sorts of additives. They published about it in the magazine Fluid physics.

A very dynamic process

Crystals form naturally, which is both what physics dictates and what you see happening on the kitchen counter. But after that it quickly becomes more exciting. Crystal formation is far from uniform. A first indication for this was the force used by the kneading machine, which is an indication of friction during kneading. Although the crystals apparently grew, they became fewer and fewer. Then it peaked and then got pretty consistent again at a higher level. What is happening here?

It was pretty accurate with the other measurements. Indeed, there were more and more crystals bigger and bigger. But energy is released both during their formation and from the additional friction produced by the kneading of these crystals, which counteracts the cooling of the mixture, which reduces the friction somewhat. There was also a second effect, which reduces net friction, the researchers say. The sugar that has settled in these crystals is thus eliminated from the liquid, which therefore has a lower sugar concentration. And the more watery the mixture, the less resistance there is.

Then comes the second part of the act, easy to follow under the microscope. At one point, in the lab after about 10 minutes, there are so many crystals that are so big that they themselves start breaking into smaller ones. This is where the kneading machine suddenly becomes heavy. During this time, the remaining liquid sugar continues to crystallize, but since clumping begins later, smaller crystals also remain. The result: a fairly homogeneous mixture. Under the microscope, it was seen that the crystals vary much less in size in this phase. And it was also visible on the mess. It had lost more strength, the fondant is thick, but at an almost constant level.

It is not true that Hartge wants to venture into the perfect fondant recipe based on these findings. She believes that process information can help improve control of the crystallization process in the plant. It can also help in finding sucrose alternatives that provide a similar texture. In short, healthier pink cakes. And during this time, everyone can reflect on the wonderful process that takes place under their hands when kneading fondant.

The study appeared in the newspaper this week Fluid physics.

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