The removal of shell is an important step in the process of making cocoa mass. Codex standard n. 141–1983, rev 1–2001 by Codex Alimentarius sets maximum tolerance values for cocoa shell in chocolate mass. Apart from the legal requirements, proper removal of shell is a prerequisite for a good quality product: Shell, by its very nature, is exposed to external factors and will have picked up undesirable contaminants.
Shell does not contribute positively to the flavor of the final product and may indeed produce off-flavors. Being a very fibrous material, it is extremely ‘hard’ and consequently difficult to grind which leads to abrasion of the grinding equipment.
Moreover, shell separation from the nib influences the yield, and the loss of small nib particles along with the shell is a particularly important financial factor. Ideally, the shell should separate perfectly leaving large pieces of shell and almost the intact nib. The shell around some beans cannot be removed easily however, with certain origins being particularly difficult.