Diagnosing Chocolate's Quality With Ultrasound

What's the difference between a cheap piece of Hershey's and a luxurious bite of the finest Belgian chocolate? According to a team of researchers in Leuven, Belgium, the secret lies in cocoa butter crystals. And now they've developed a novel way to use ultrasound to check on cocoa butter crystallization.

"We've discovered that we can detect differences in the crystallization of cocoa butter with ultrasonic waves," says Koen Van Den Abeele, a physics professor at KU Leuven, Belgium's largest university, in a press release. He is an expert in using ultrasound to test metals and concrete — considerably less tasty materials.

Currently, top chocolatiers closely monitor batches of cooling chocolate by running samples to an on-site lab to test for cocoa butter crystallization. If the wrong crystals form, the whole batch will need to be reprocessed, a time-consuming and costly mistake.

But by using ultrasound, the Belgian researchers can monitor the internal structure of cocoa butter crystallization in real time without sacrificing an ounce of precious chocolate.

"Cocoa butter crystallizes 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," says Imogen Foubert, a professor in the department of microbial and molecular systems at KU Leuven in a press release. The sought-after crystals deliver the snap when you get when you first bite the chocolate as well as its rich, melting mouth feel.

Van Den Abeele sends transversal ultrasonic waves through the cooling chocolate to get a clear picture of the crystal structures forming inside, not unlike an ultrasound technician checking on the health of a growing fetus.

"When the cocoa butter is liquid, the ultrasonic wave is reflected in its entirety," explains Van Den Abeele. "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."

The next step for the Belgian research team is to upgrade their lab prototype into a factory-grade chocolate testing machine. Hopefully this won't put any chocolate tasters out of a job.