The word "conche" derives from the word "concha" for "shell", inspired by the snail shell-like shape of the drive wheel of a classic conching machine.
Behind the sonorous name of the conche is a chocolate-making device that has contributed significantly to the worldwide success of the brown delicacy. Around 1870, when the production of chocolate bars was still in its infancy, Rodolphe Lindt discovered (according to stories by chance) an improvement in the quality of chocolate after hours of grinding and rolling. Not only was the chocolate finer, but the product was altogether more edible. Before, chocolates were mainly bitter and a little sandy on the palate. Now he had managed to bring out the fine flavours of the cocoa and achieve a velvety texture.
Why conching?
It has already become clear in the introduction what is intended by conching: An overall improvement in the quality of taste and texture.
If we take a closer look at the effects of conching, it also becomes clear to what extent it can improve chocolate. First of all, it is about the size of the particles: The movement in the conche makes the particles finer, which influences the mouthfeel. In addition, the particles also become rounded, similar to how grains of sand become finer and rounder in the constant back and forth of the waves.
This also distributes the ingredients of the chocolate more evenly. In the case of dark chocolate, this concerns cocoa mass and sugar; in the case of milk chocolate, milk powder is added. In addition, the supply of hot air evaporates excess moisture. Trapped water can lead to faster spoilage, discolouration and similar defects.
In addition to the mechanical process, however, something also happens on a chemical level: the contact with air oxidises undesirable flavours (including acetaldehyde, acetone, i-butanol, ethanol, i-propanol, ethyl acetate, acetic acid, i-pentanal, methanol, diacetyl), which show up in the taste as acids or bitter substances. Thus, with the conche, the chocolate maker has another possibility to produce the best possible version of his chocolate.
Sources:
Making Chocolate, Todd Masonis, Greg D’Alesandre et. Al., 2017
Schokoladenherstellung, Theobroma-cacao.de