Cocoa powder is a powder which is obtained from cocoa solids, one of the two components of chocolate liquor. Chocolate liquor is a substance which is obtained during the manufacturing process which turns cacao beans into chocolate products. This powder can be added to baked goods for a chocolatey flavor, whisked with hot milk or water for hot chocolate, and used in a variety of other ways, depending on the taste of the cook.
Before delving into the specifics of cocoa powder, it may help to explain the process through which cacao beans are turned into chocolate. These beans are harvested in large pods which are split open and then allowed to ferment, mellowing the natural bitterness of the beans. After fermentation, cacao beans are roasted and then hulled to expose the cacao nibs, which are then ground to produce chocolate liquor, a gritty, runny paste which is the first step in creating a dizzying array of chocolate products.
Once cacao nibs have been ground into chocolate liquor, the chocolate liquor is pressed to squeeze out the rich cocoa butter. Without pressing, the chocolate liquor would be greasy, fatty, and very unpleasant, even with the addition of sugar and spices. The pressing separates the chocolate liquor into two components: cocoa butter, and cocoa solids. To produce cocoa powder, the cocoa solids are pressed again, ensuring that around 75% of the original cocoa butter has been removed, and creating a substance called press cake. The press cake is dried, and then ground into powder.
There are two main types of cocoa powder. Natural cocoa powder is produced using the process detailed above, and it is naturally very strong, slightly acidic, and very dark. Dutched cocoa powder or Dutch cocoa is produced by adding an alkali to the press cake to mellow the flavor and make the color less intense. Because Dutch cocoa is alkalized to remove the natural acidity, it is important to read baking recipes which call for cocoa carefully, as replacing natural with Dutch cocoa can cause a baked good to rise poorly or unevenly. Pure cocoa powder is very intense and bitter. To make it usable, most people add sugar to temper the chocolate flavor, and other spices such as vanilla may be added as well.