Science News

Electricity produces low-fat chocolate

Fri, 24th Jun 2016

Claire Armstrong

Applying an electric field to chocolate during production makes it possible to cut theChocolate 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.


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I am obese. I don't eat chocolate. So the answer is "no".

The solution to obesity is to turn off the central heating (you burn about 1800 kCal per day to maintain body temperature in a 15 degree ambient, more at lower temperatures or with wind chill) and eat less of everything. Why do people mess about with complicated chemistry when the answer is simple physics?  alancalverd, Sat, 25th Jun 2016

I think the answer is in your response. You didn't become obese by eating air... Chocolate is one thing and yes you may eschew it, but there are other foodstuffs that clearly you do consume that are similarly over-stuffed with calories. Cutting the energy density of some of those foods might help you and others like you.

People could go for a walk and burn 400 kCal/hr, but they don't. Nor will they sit at home and shiver. It's human nature. chris, Mon, 27th Jun 2016

That's 470 watts. The highest continuous useful output recorded for a human was Bryan Allen, the Kremer Prize manpowered aircraft pilot, a professional cyclist who could sustain 300W for an hour. Farm workers and navvies can manage about 75W continuous for a 4-hour shift, which is why we use tractors.

Most of the energy loss in walking is thermal. Crosscountry skiing for 6 hours without a hat, at -10 deg C, I burn at least 6000 kCal per day, but walking the same track in summer, less than 2500.  A good friend who was caught in an Alpine snowstorm roped himself to the mountain for 2 days, ate 12000 kCal of emergency rations, and lost 2 kg weight (mostly by evaporation). He then completed the climb, fell over in the icy car park, and broke a leg. Hubris.

The only things that will kill you are not enough of what you need, or too much of what you like. I woldn't recommend either to a youngster, but it was an easy choice for a 72-year-old ex prop forward who played his last game of rugby on his 60th birthday. Nevertheless it would be nice to wear Speedos again without embarrassment, so who knows? alancalverd, Mon, 27th Jun 2016

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