Belgian researchers monitor chocolate quality with ultrasound

Belgian chocolate is famous all over the world. But producing a delicious bar of chocolate that has all the desired qualities, and maintains them throughout its entire shelf life, is not easy. Now Belgian researchers have developed a new way to check the quality of their country’s most famous product.

The final quality of chocolate largely depends on the crystals that form during the hardening of the chocolate. Chocolate manufacturers currently check the quality of their chocolate ‘offline’. A sample is taken from the production line to be analysed in a lab, which is a time-consuming process that makes it impossible to intervene quickly when something is wrong. As a result, a large amount of chocolate is destroyed or reprocessed — a costly affair.

Researchers have now developed a quicker way to check whether the cocoa butter is crystallising correctly during the hardening process. The technique can be used ‘online’ to check the chocolate while it’s still on the production line, potentially saving the industry both time and money.

“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. The number, size, shape, and the way in which the crystals stick together, play an important role as well,” explained Professor Imogen Foubert from the KU Leuven Department of Microbial and Molecular Systems.

“We’ve discovered that we can detect differences in the crystallisation of cocoa butter with ultrasonic waves,” added Professor Koen Van Den Abeele from the KU Leuven Department of Physics and Astronomy.

The new technique involves sending transversal ultrasonic waves through the cocoa butter. The 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. This enables us to see how the different crystals stick together, which is important for the ultimate properties of the chocolate,” said Professor Van Den Abeele.

The researchers have designed a lab prototype, which now needs to be turned into a prototype for use in real chocolate production lines. The current results were obtained with cocoa butter and need to be confirmed for actual chocolate.