If you bake with cocoa you have probably noticed recipes that call for either Dutch-processed or natural (non-Dutch-processed) cocoa powder. What is Dutch process cocoa powder, and how will it affect your chocolate recipes?
The first thing to understand is that cocoa is a mild acid. Regular cocoa powder is made from cocoa nibs - the inner kernel of the cacao bean (see the cacao bean in its natural state). These nibs have been pressed to remove part of the cocoa butter, leaving some cocoa fat and compressed cocoa particles. These are ground and the final product is a fine powder with a pH of about 5.5.
This is natural, unsweetened cocoa powder. So what's the difference with Dutch process? Dutch process cocoa powder is treated with an alkaline solution. This partially neutralizes the acid in natural unsweetened cocoa powder. If you buy a Dutch process (or alkalized) cocoa powder you will immediately notice that it has a darker color than the reddish natural powder.
It also has a smoother, darker flavor which, unexpectedly, is actually less intensely chocolate in taste, sometimes. The strong acids that characterize bitter chocolate flavor are smoothed out. We've talked about Hershey's Special Dark Cocoa, which is actually a rather good Dutch cocoa for certain purposes. It is the thing to use if you are looking for a very black chocolate - Oreos and Whoopie Pies come to mind.
Now, here's the tricky thing. You need to pay attention to the kind of cocoa a recipe calls for. Remember our discussion of baking powder and baking soda? Different levels of acid in a recipe affect the leavener, so the different pH level in regular and Dutch cocoa can radically affect how your baked goods rise (or not).
Dutch cocoa usually has a pH of 7 or 8, as opposed to natural cocoa's 5.5. So be careful in substituting one for the other.