The physics behind what makes chocolate so smooth has been revealed by researchers studying a 140-year-old mixing technique.
Scientists at the University of Edinburgh studied the process of conching, which involves mixing ingredients for several hours.
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.
Before the invention of the conching process, which was developed by Swiss confectioner Rodolphe Lindt in 1879, chocolate had a gritty texture.
This was because the ingredients form rough, irregular clumps that do not flow smoothly when mixed with cocoa butter using other methods, the researchers said.
The new research reveals conching produces smooth molten chocolate by breaking down lumps of ingredients into finer grains and reducing friction between particles.
It is hoped the findings may hold the key to producing confectionery with a lower fat content, and could help make chocolate manufacturing more energy efficient.
Professor Wilson Poon, of the university’s school of physics and astronomy, who led the study, 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 confectionery product.
“By studying chocolate making, we have been able to gain new insights into the fundamental physics of how complex mixtures flow.
“This is a great example of how physics can build bridges between disciplines and sectors.”
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.