What actually happens when you make fondant? These scientists discovered it

Delicious and distinctive, a delight on the tongue. Fondant makes many people’s hearts beat faster. Also from physicists, because they find there’s still a lot to learn about exactly how fondant is formed.

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

To find out, Hannah Hartig and her colleagues from the Max Planck Institute set to work using an industrial fondant-making machine. You can set and observe these devices very precisely, and if you also put sugar water under a microscope at different stages, you will learn a lot. They used the simplest fondant you can imagine, made of water and granulated sugar, so that their view of the process would not be affected by all kinds of additives. They published about it in the magazine fluid physics.

A very dynamic process

Crystals form naturally, which is dictated by physics and what you see happening on your kitchen counter. But then it quickly gets more exciting. The crystal composition is far from uniform. The first indication of this was the force applied by the kneading machine, which is an indication of friction during kneading. Although the crystals seemed to have grown, they were becoming fewer and fewer. Then it peaked and then became steady again at a higher level. What is going on here?

This was fairly accurate with the other measurements. In fact, there were more and more larger crystals. But the energy is released during their formation and the extra friction that results from kneading those crystals, hinders the cooling of the mixture, which in turn reduces the friction somewhat. The researchers theorize that there was also a second effect, that of reducing net friction. Thus, the sugar that has settled into those crystals is removed from the liquid, and thus contains a lower concentration of sugar. The more water in the mixture, the lower the resistance.

Then comes the second part of the act, which was easy to follow under a microscope. At some point, in the laboratory after about 10 minutes, there are many crystals that are so large that they themselves begin to split into smaller crystals. This is where the kneading machine suddenly becomes heavy. Meanwhile, the remaining liquid sugar continues to crystallize, but because it starts to clump later, it also remains with smaller crystals. The result: a fairly even mixture. Under a microscope, it is observed that the crystals vary in size to a much lesser extent at this stage. It can also be seen on the kneading machine. It has lost more power, and the anvil is thick, but at a roughly constant level.

It’s not that Hartig would want to gamble on the perfect fondant recipe based on these results. She believes the insights into the process can help improve control of the crystallization process in the factory. It can also help to look for alternatives to sucrose that produce a similar texture. In short, healthier rosy cupcakes. And in the meantime, everyone can contemplate the wonderful process that takes place under their hands while kneading fondant.

The study appeared in the journal this week fluid physics.

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