London | Researchers have developed a new and quicker method to check the quality of chocolate using ultrasound, which could save the industry a lot of money. Producing a divinely delicious bar of chocolate that has a beautiful gloss, makes that wonderful sound when you break it, melts in your mouth, and maintains all these qualities throughout its entire shelf life, is not easy, researchers said.
The crystallisation of the cocoa butter – the fat in the chocolate – plays an important role in that process. Cocoa butter crystallises as the liquid chocolate hardens. Five types of crystals can be formed during this process, but only one of these has the qualities we want, said Imogen Foubert from KU Leuven University in Belgium.
The number, size, shape and the way in which the crystals stick together play an important role as well, said Foubert. We have discovered that we can detect differences in the crystallisation of cocoa butter with ultrasonic waves, added Koen Van Den Abeele from KU Leuven.
The new technique involves sending transversal ultrasonic waves through the cocoa butter. Researchers then measure the reflection of these waves for information about the structure of the butter.
The technique is similar to the ultrasound echography used to monitor the health and growth of foetuses in the womb. When the cocoa butter is liquid, the ultrasonic wave is reflected in its entirety.
As soon as the butter crystallises, part of the sound wave penetrates the cocoa butter, so the amount of reflection we measure changes, researchers said. This enables us to see how the different crystals stick together, which is important for the ultimate properties of the chocolate, they said. Chocolate manufacturers currently check the quality of their chocolate ‘offline.’
A sample is taken from the production line to be analysed in a lab. This method is very time-consuming, making it impossible to intervene quickly when something is wrong, researchers said.
As a result, a large amount of chocolate is destroyed or re-processed – a costly affair. The novel technique can be used ‘online’ to check the chocolate while it is still on the production line, they said.