The Mysteries of Roasting

The three big processes that determine the flavor of chocolate are fermentation, roasting, and conching. These are the steps where the art of chocolate making really lies, and also the steps that seem to be the least understood in the scientific literature on chocolate. Fermentation has to happen nearly immediately after the cacao pod is harvested from the tree, so is a hard variable to control for, unless you are a huge chocolate company, or a committed chocolatier willing to spend part of your year on a plantation like Steve DeVries. Perhaps some day I’ll be able to experiment with this process, but for now, I have to content myself with tweaking roast and conching to develop chocolate flavor.

S. Beckett’s encyclopedic tome “Industrial Chocolate: Manufacture and Use,” despite it’s forbidding title, actually has some interesting clues for small batch producers. Buried in section 5.8, R.F.M. Heemskerk mentions two interesting studies that sound like good jumping off points for tweaking my next batch. The first is a study by Zeigleder and Oberparleiter in 1996: “Aromaentwicklung in Kakao. Auswirkung der feucht-thermischen Behandlung.” The upshot of this study is that steaming nibs to add about 15% water, then doing a slow pre-roast at 40-60C to reduce the moisture, followed by a full roast at 98-100C develops more cocoa flavor precursors, and yields a chocolate with a more intense taste. Having water present seems to facilitate the sugar/amino acid reactions that form chocolate flavor during the roast. This is yet another scientist proposing using water, chocolate’s natural enemy!

The other study mentioned by Heemskerk is Mohr, et. al., 1978, in “Uber die Grundlagen der Aromaveredelung von milchfreien und milchhaltigen Shokoladen-massen.” The finding here is that optimal development of chocolate flavor is accomplished by a slow pre-roast, lowering moisture in the cacao bean to about 3% before rapidly increasing the temperature to the final roast temperature.

Both of these ideas seem simple enough to try, though it’s going to be an incredible pain to build some parallel batches to compare the taste of the final product under different roast conditions if I’m going to go all the way to completed chocolate.


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