Electricity produces low-fat chocolate

Applying an electric field to chocolate during production makes it possible to cut the fat content by more than 10%...

Cocoa solids, a key component of chocolate, are thought to boost our mood, lower our blood pressure and even improve circulation.  However, with a fat content of around 40%, chocolate itself doesn't do wonders for your waistline! An obvious solution is to engineer low-fat chocolate, but it's not as easy as it sounds.

Reducing the fat in chocolate increases its viscosity or stickiness, making it too thick to process because it clogs the machines used to make it. To bypass this problem, some chocolate manufacturers replaced the fat from the cocoa butter with a low-calorie fat, but a ban on such fats in several countries owing to concerns about safety, means chocolate made this way cannot be sold.

Now a team of researchers at Temple University in Philadelphia have discovered that using an electric field makes it possible to remove some of the fat in chocolate, without it ending up too gooey to process.

In its liquid form, chocolate consists of many small round solid particles containing cocoa, milk solids and sugar. These components are suspended in droplets of liquid fat and oil. This is known as a suspension.  Einstein showed during his career that the viscosity of a suspension is not only dependent on the fraction of solid particles present, but also on their shapes.

A suspension with a small fraction of solid particles will be less viscous than that with a higher fraction. Think of adding flour to water - the more flour particles there are, the thicker it becomes.  What's more, a suspension with round particles - like apples - will be thicker than a suspension where the particles are long and oval shaped - more like bananas, which all point in the direction of flow and can slide over each other.

Applying an electric field along the flowing stream of the liquid chocolate causes some of the round solid particles to clump together along this direction, forming slightly larger, banana-shaped particles.  Such a change in the shape of the particles means the viscosity of the chocolate is reduced, and it can flow more easily.

This technique is known as electrorheology and means that more than 10% of the liquid fat can be removed from the chocolate before it reaches the viscosity limit for processing.

Interestingly the team report no negative effect on the taste of the chocolate when it was processed using the electric field. "I couldn't tell the difference," explains Professor Rongjia Tao, head of the team conducting the study.  Indeed some people claimed that the fat reduced chocolate tasted better, as it had a higher cocoa content.

The technique can be applied to all types of chocolate, even white chocolate, and the team expect that we will see a new class of fat reduced chocolate soon.  "This will be very big for our society," Tao predicts.