During chocolate production, the cocoa bean is milled and grinded to produce cocoa liquor, which is a mixture of cocoa solids and cocoa butter. The cocoa solids and cocoa butter are then extracted from the liquor. Cocoa powder is the pulverized version of the cocoa solids extracted.
Cocoa Powder is a starch, so it should be treated as a starch. When people refer to “activating” cocoa powder with hot/boiling water, they are referring to the process of gelatinization. The starch bonds in cocoa powder are disrupted by heat and then displaced by water molecules. This causes the starch to leak into the water. In addition to starches, fats and flavoring compounds are also released into the liquid. This allows for the fats and flavoring to be distributed throughout the batter/dough of whatever is being made.
There are two types of cocoa powder on the market. These are Natural and Dutch processed. Dutch processed has been alkalized, so that it no longer has the acidity or original color of cocoa powder. As a result of being alkalized, it also has a less intense flavor. Natural processed has a pH of 5.5, which can be very useful in controlling the rise of baking soda and baking powder leavened products.
Cocoa powder can be used for a wide variety of foods. If added directly into batter, then the product will have a chocolatey taste. Although, this addition only adds the flavor and not the cocoa fat, which is the main attraction in the taste of chocolate. Cocoa powder is amazing in hot chocolate. I prefer chocolate to just cocoa powder, whenever possible, because the cocoa fat delivers in taste and texture.