What Is Conching?
The short answer
Conching is a long stretch of mixing, often with heat and air, that chocolate goes through after refining and before tempering. It lowers the overall level of aroma compounds and turns a thick, pasty mass into chocolate that pours.
How it works
Straight out of a roller refiner, the particles are already fine, but the mass is a dry, crumbly flake. Chocolate from a melanger or a ball mill comes out fluid. Either way, it still carries water and volatile compounds, including acids such as acetic acid from fermentation. A conche keeps it moving for hours, and many of those volatile compounds escape, including some of the water and part of the acids. Individual acids don’t always follow the pattern: in one study acetic acid rose during conching and ended above its starting level. Industrial conches are heated; a melanger warms up from friction.
The constant working also spreads cocoa butter over every particle of sugar and cocoa. That is what makes the chocolate thin out and feel smooth in the mouth. An emulsifier such as lecithin is often added near the end of the cycle.
How long and how warm is the maker’s call, and it changes the flavor. There is no single right setting; it depends on the beans, the recipe and the machine.
Where you’ll see it
On spec sheets for conches and refiner-conches, in a bean-to-bar maker’s process notes, and in any explanation of why two chocolates made from the same beans can taste different.
Related terms
Conching follows refining and sits right before tempering. It is one of the main things a maker adjusts to control viscosity. Smaller producers often use a melanger or a refiner-conche, so one machine handles both refining and conching.