Researchers from KU Leuven (Kulak Kortrijk Campus) have now developed a new and quicker way to check whether cocoa butter is crystallising correctly during the hardening process.

An important find if you keep in mind that cocoa butter crystallization is key in the chocolate production process so that it shines, melts in the mouth, and keeps its properties for a long time. “Cocoa butter crystallizes as the liquid chocolate hardens”, explains Professor Imogen Foubert from the KU Leuven Department of Microbial and Molecular Systems. “Five types of crystals can be formed during this process, but only one of these has the qualities we want. The number, size, shape, and the way in which the crystals stick together play an important role as well”.

The new technique, which consists of sending transversal ultrasonic waves through cocoa butter, allows researchers to measure the reflection of these waves to obtain information on the butter’s structure. “When the cocoa butter is liquid, the ultrasonic wave is reflected in its entirety. As soon as the butter crystallizes, part of the sound wave penetrates the cocoa butter, so the amount of reflection we measure changes. This enables us to see how the different crystals stick together, which is important for the ultimate properties of the chocolate”, says Professor Koen Van Den Abeele from the KU Leuven Department of Physics and Astronomy.

The findings are the result of Annelien Rigolle’s interdisciplinary doctoral research, supervised by Professor Imogen Foubert, who specialises in fat crystallisation, and Professor Koen Van Den Abeele, who is an expert in the use of ultrasound for non-destructive testing of materials such as composites, metals, and concrete. The researchers designed a lab prototype, which now needs to be turned into a prototype for use in real chocolate production lines.