When is the best time to add the sugar and cocoa butter in the grinding process?
There isn’t one.
That said, you have some choices and those choices have the potential to change how your chocolate behaves and tastes.
I personally like to add the ingredients in the order that makes my life easier and does not over stress the machines. That means melting my cocoa butter, and lecithin if I am using it, and adding it to my warmed melanger bowl (the stones are warm too). This gives you what is called a working fluid. The melangers were after all initially WET grinders. Dry material has the tendency to pack down. After that I either add my melted cocoa mass or handfuls of the warmed cocoa nibs. Every 15 minutes or so I add another handful nibs. In that time the previous addition as started flowing. Once I have a pound or two in there I usually alternate between sugar and nibs, under the premise that sugar is hard and makes a good abrasive, even if it is getting ground down at the same time. Basically it helps speed/shorten the time between additions and lets me be done sooner.
But you have lots of options. You can add the sugar as I’ve done above. Or you can wait until all the nibs are flowing. Or you can let your chocolate mass refine a few hours to a day before adding the sugar. Depending when you add it, there is the potential for the chocolate to taste different. At the beginning there are more acids and water present. Under some circumstances (yes, I am being purposefully vague because the sugar chemistry is a bit much to get into here) this can lead to chemical reactions which may or may not be to your liking. Adding the sugar just an hour later is a good halfway point, and a day later eliminates most of these type reactions. Do you want these reactions? Well, maybe. It is very subjective and to one’s own tastes. Basically you have to try it and see. I’ll say my tastes tend to liking many complex reactions so it is fortunate that I add my sugar sooner. I have also tasted chocolate made from sugar added a day later and it was a thoroughly enjoyable chocolate….just different than my own.
The same goes for cocoa butter. When it is added at the beginning, your resulting chocolate is going to be less viscous. More fluid. That means two things chemistry wise and one from a physical standpoint. When thicker, reactions are going to be a little slower, but it also means volatiles won’t be volatilized as quickly. With a thicker mass, your melanger won’t refine quite as fast as directly compared to a thinner mass. This means a longer run time but also more time for reactions to occur. It is the same as before. I like running the melanger with a thinner mix where reactions happen faster and everything is ‘set’ early. But I have again tasted batches where the chocolate was run thick, but longer, and the cocoa butter was added right at the end as a viscosity modifier. It too was great, but different chocolate, than mine.
And don’t forget, all beans are not created equal. What works (for your tastes) for one, may not yield the most favorable results for another. And sadly I can’t help or predict that in the least. All I can tell you is you have to experiment and that in some (but not all) cases additions of sugar and cocoa butter at different stages can result in pretty different results.
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