Following micronization the cocoa beans pass to winnowing machines ( see pages 272-3) where removal of the shell is com- pleted. The nibs are then roasted in a two-stage process designed to optimize product quality. A Tornado-type roaster is most com- monly used in the NARS process. This consists of an externally heated rotating drum in which nibs are heated by a combination of conduction and convection. In operation, the drum is charged with beans. Where alkalization is used (see pages 275-6) a pre-heated solution of alkali is sprayed onto the nibs before heating com- mences