On Chocolate Conching

Reader Katie asks:

Do you know anything about conching chocolate? I’d love to hear more of the science behind that process.

I know w a little bit, Katie, but not terribly much. For while conching is a very well-known step in chocolate processing, it’s something chocolate manufacturers don’t say much about. That’s partly because some believe that conching is the step in which the magic happens. Others, interestingly, think the supposed “mystery” of conching is just a bunch of baloney. I’ll leave that to you to decide.

Conching is a mashing/mixing/blending step in chocolate manufacture. It’s the last step in the process, the one in which the refined chocolate liquor is agitated and steadily combined with the other things that make confectionery chocolate what it is: cocoa butter, flavorings, milk solids, emulsifiers, etc.. Aftrer conching the chocolate is ready to be extruded in to molds and set. It’s called “conching”, supposedly, because the original conching vessels were shell-shaped. I’m not totally sure about that, but it seems reasonable enough.

These days conching happens in large containers, and can occur in one of several ways. Some conching machines look like big stand mixers that smear chocolate continuously along the inner wall of a vat. Others contain big stone wheels that roll around and around in a circle, pressing the chocolate and steadily mixing it.

Yet the idea isn’t really to grind down the chocolate particles (the cocoa solids are ground and refined in an earlier step) so much as to roll them around over each other repeatedly. This is thought to round off the edges of the particles like so many stones in a rock polisher. What does that do? Some say it mellows the chocolate’s flavor, others that it improves the mouthfeel. Still others that it adds an ineffable special “something” that can’t be described but that tasters can recognize.

That aside, it seems that conching might do other things, too. The friction of the conching process raises the chocolate’s temperature for an extended period. That might evaporate some water from the mixture, or possibly destroy and/or release volatile/bitter/acidic/tannic compounds. The constant aeration might cause some of the chocolate components to oxidize (react with oxygen). No one really knows. And when I say no one I mean no one. Chocolate, like coffee, contains literally hundreds of different chemical compounds, some of which are understood, most of which aren’t. So what happens chemically in the conch is pretty much anybody’s guess.

All that said it’s easy to see why conching has near-religious significance for some chocolate makers, none at all for others. Some conch their chocolate for a week, some for a few hours, some skip the step completely. If I were Willy Wonka, would I conch my chocolate? Probably, if only because it seems like a good way to mix all the components of chocolate together and make sure they’re thoroughly blended. If conching does anything, it certainly does that.