Edinburgh University researchers discover science behind best chocolate

THE science behind great chocolate has been revealed by experts studying a 140-year-old mixing technique.

A woman working in a chocolate shop.

Researchers at the University of Edinburgh have uncovered the physics behind the process – known as “conching” – which is responsible for creating the distinctive smooth texture.

The team studied mixtures resembling liquid chocolate created using the process, which was developed by Swiss confectioner Rodolphe Lindt in 1879.

Their analysis, which involved measuring the density of mixtures and how they flow at various stages of the process, suggests conching may alter the physical properties of the microscopic sugar crystals and other granular ingredients of chocolate.

It is hoped the findings may hold the key to producing confectionary with lower fat content, and could help make chocolate manufacturing more energy efficient.

Until now, the science behind the process was poorly understood, but the new research reveals that conching – which involves mixing ingredients for several hours – produces smooth molten chocolate by breaking down lumps of ingredients into finer grains and reducing friction between particles.

Chocolate had a gritty texture prior to the invention of conching due to the base ingredients forming rough, irregular clumps when mixed with cocoa butter.

Lindt perfected the conching process by mixing, stirring and aerating liquid chocolate using a “conching machine”, leaving the molten mass to be smoothed out over several days.

The process is still practised by Lindt’s chocolatiers in Switzerland, Germany and France in modern times.

The study, published in Proceedings of the National Academy of Sciences, involved a collaboration with researchers from New York University.

The work in Edinburgh was funded by Mars Chocolate UK and the Engineering and Physical Sciences Research Council.

Professor Wilson Poon, of the University of Edinburgh’s School of Physics and Astronomy, who led the study, said he hoped the research could improve the way chocolate is produced. He said: “We hope our work can help reduce the amount of energy used in the conching process and lead to greener manufacturing of the world’s most popular confectionary product.

“By studying chocolate making, we have been able to gain new insights into the fundamental physics of how complex mixtures flow.”

Prof Poon added: “This is a great example of how physics can build bridges between disciplines and sectors.”