Destoners are an essential part of the roasting process, serving as insurance and that extra layer of protection for your equipment and Ublend coffee.
Most countries that grow coffee still use a very low-tech, yet tried-and-tested, way to process and dry coffee beans. This often includes spreading the washed and processed beans across concrete to let them naturally dry out. When they are gathered back up, other items like crumbled concrete, twigs, metal, nails, and actual small stones (hence, the name), will be gathered up with them.
When the beans are released from the roaster’s cooling tray, they spill down into a holding tub at the bottom of the destoner. The roasted coffee is then sucked from this tub up a narrow chute, then eventually into a silo.
All the unwanted extras collect at the bottom of the destoner. This can also include coffee beans that didn’t roast properly because they were underripe. These defective beans are called Quakers.
The destoner is essentially the last step removing any stones or under roasted beans before packaging.