After roasting, the next step in the chocolate making process is to crack and winnow the cacao, with the end result being a separation of the nib (cotyledon), shell (husk) and germ (radical). Generally speaking, the makeup of your average cacao bean is going to be 87% nib, 12% shell and 1% germ. For making chocolate, it is ideal to remove as much of the shell and germ as possible because these parts of the cacao bean are mostly indigestible and are bad for flavor.
The basic process of winnowing involves an initial crack of the bean. During this step, it’s important not to crack the bean too vigorously because that can lead to the formation of fine particles. Overly fine shell and nib particles can’t be used for fine chocolate because it is too difficult for the winnower to differentiate between the two. The goal of a good crack is to keep the nib as large as possible while simultaneously separating the shell and dislodging the germ (the germ is a part of the seed that later grows to become the stalk).
Now at this point, the cracking has separated the three components of the cacao seed, but now the nibs have to be sifted out to be used for making chocolate. There are endless ways to do this and dozens of large machine designs that all work fairly well. The basic principle behind winnowing is that the shell is less dense than the nib, so if the correct velocity of blowing air is used, then the shell should blow away, leaving the nib behind. A hairdryer and a big bowl does a pretty good job of this; or just throwing a heap of cracked beans in front of a large blowing fan; or if you have plenty of time on your hands and good dexterity, you can hand-peel each bean.
The larger winnowers use a series of sieves to sort the mass of cacao pieces into common sizes. Then, these divided groups of particles are exposed to varying air currents that are ideal for each size—blowing away the shells and dust and leaving the nibs behind to be used for making chocolate.
Winnowing is a highly important step in the chocolate making process because a poor process can lead to poor tasting chocolate. It doesn’t matter how revered the beans if the final chocolate has a high percentage of cacao shells. Also, if the air currents are too strong for the particle size, a good percentage of the nibs can be blown away with the shell, creating a great deal of inefficiency. So as you can see, winnowing, in theory, is fairly basic, but in application it is one of the most demanding steps of the chocolate making process.