Science & Environment

Chocolate and agar recipe can halve the fat

Women working on a chocolate bar production line
Image caption The new method can be easily adapted to existing chocolate manufacturing

Chemists have found a new way to halve the fat of chocolate using liquids which does not change the "mouthfeel".

Low-fat preparations of chocolate are well known, but their textures tend not to match the real thing.

A report at an American Chemical Society meeting described a method using the popular gelling agent agar to make tiny "sponges" that displace fat.

University of Warwick researchers said water, fruit juice or even alcohol could replace up to half the fat.

When used with alcohol, Stefan Bon said they were like "tiny vodka jellies".

What has held up such chemistry is making what is known as an emulsion - a thorough blend of materials that do not tend to mix, such as oil and water.

Normal chocolate gets much of its velvety feel from an emulsion of fat globules suspended within the solid.

Replacing those is tricky - any substitutes have to remain dispersed throughout the chocolate as it is heated and cooled to a solid, and they have to remain small.

Dr Bon said that the smooth texture of chocolate requires that the globules be smaller than about 30 millionths of a metre across - about half the width of a human hair.

Image caption Normal chocolate gets its velvety feel from an emulsion of fat globules suspended within the solid

The Warwick team first published an attempt to crack the problem in a 2012 paper in the Journal of Materials Chemistry.

That formulation made "armoured" spheres of liquid, using two materials - fumed silica, a form of the same material from which sand is made, and chitosan, a compound derived from shellfish.

'Not healthy, but exciting'

That solution required that the liquid be slightly acidic, so the team used fruit juices.

"That was exciting because it had the combination of fruit juice and chocolate, and everybody went wild on it," Dr Bon told BBC News.

"Then some people - especially in the UK - said: 'but can we do alcohol?'

"We've been working very hard in the lab to make a system that can do that - instead of these armoured systems we then thought we could make tiny little vodka jellies."

The new approach is simpler to carry out and more versatile in the replacements it can employ.

It also avoids any concerns consumers may have with the nano-structured fumed silica, or dietary restrictions on eating shellfish products.

"So you can stick to your fruit juice if you want, but you can also make a vodka-based chocolate bar, which is exciting - obviously not very healthy, but exciting," Dr Bon said.

On a healthier note, he added that using the method with other liquids could lead to significantly reduced sugar content as well.

"It opens the route to different types of confectionery candy that can be placed on the shelf next to everything else that's out there already," he said.

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