With A Zap, Scientists Create Low-Fat Chocolate

By Mark H. Kim

Published June 25, 2016 at 12:29 PM EDT

Physicists say they've discovered how to zap the fat out of chocolate.

The researchers, led by Rongjia Tao of Temple University, were able to remove up to 20 percent of fat by running liquid milk chocolate through an electrified sieve. And they say the chocolate tastes good, too.

Before they're foil-wrapped bundles that make chocoholics smile, chocolate bars start out as liquid in a factory: delicious particles of cocoa solids (which give chocolate its characteristic flavor) sugar and mixed solids, suspended in melted fat and oil, mostly cocoa butter (typically, up to 40 percent by volume). The cocoa butter is essential for keeping the liquid chocolate flowing smoothly through factory pipes.

When a consulting firm working for candy giant Mars Inc. reached out to Tao back in 2012, it wanted his help in improving the viscosity of liquid milk chocolate. Tao's team worked out a method of making the chocolate flow even better than normal through the pipes — without adding any more cocoa butter.

Then the researchers had a Eureka moment: If they could make liquid chocolate flow better without any extra cocoa butter, they could also slash the fat in it — by 10 to 20 percent — and still make it flow well enough not to jam the pipes.

Tao studies smart fluids — liquids whose properties can be transformed by applying an electric field. For example, a smart fluid may thicken rapidly upon receiving an electric shock. Most smart fluids are machine oils, but, curiously, liquid chocolate is also a smart fluid.

When you look at liquid chocolate at the microscopic level, the cocoa solids are circular, suspended in the fat and oil of the cocoa butter. These circular particles can pack together and get jammed (like a glass full of golf balls). Adding cocoa butter helps get the cocoa solids moving again.

But Tao and his team figured out how to use electricity to get the flow going. The researchers inserted an electrified sieve into the liquid chocolate. When the cocoa particles passed through the sieve, they receive an electric shock. That makes the cocoa solids flatten and start behaving like little bar magnets, lining themselves up into long chains. This chain formation allows more room for the liquid chocolate to flow.

Why? Flat objects pack tighter than round objects — the so-called "M&Ms pack more tightly in your mouth than gumballs" effect. More room means smoother flow — all without adding more cocoa butter.

Previously, manufacturers trying to lower the fat content in their chocolate could only reduce fat content to about 36 percent. But Tao and his colleagues say their method allows them to slash fat content down to 28 percent.

The title of the researcher's paper, published this week in the Proceedings of the National Academy of Sciences, promises that this electric shock method "leads to healthier and tastier chocolate." The research was funded in part by Mars. Alas, the paper supplies no data to support this titular claim about improved flavor. John Hayes, a food scientist and the director of the Sensory Evaluation Center at Penn State University, is skeptical.

"Part of what makes chocolate so unique is the melting properties of the cocoa butter," Hayes says. "It just melts exactly at body temperature." That's part of the pleasure we experience when a chocolate square melts in our mouth. Presumably, changing the amount of cocoa butter in chocolate would also change this experience. "Less butter would mean more powdery, more brittle, more stringent" chocolate, Hayes says.

Sounds to us like it would taste more like dark chocolate. However, since the researchers didn't include tests for taste and texture, it's hard to know how the zapped chocolate measures up, Hayes notes.

So is electrified, low-fat chocolate coming to a store near us? Tao says he is working with a "major chocolate company" to give his electric-field technology a real-world test run.