The coffee roasting process follows coffee processing and precedes coffee brewing using raw beans. It consists essentially of sorting, roasting, cooling, and packaging but can also include grinding in larger scale roasting houses. In larger operations, bags of green coffee beans are hand or machine-opened, dumped into a hopper, and screened to remove debris. The green beans are then weighed and transferred to storage hoppers. From the storage hoppers, the green beans are conveyed to the roaster. We typically roast at temperatures between 220 - 240 °C , and the beans are roasted for a period ranging from 16 to 24 minutes. Initially, the process is endothermic (absorbing heat), but at around 175 °C (347 °F) it becomes exothermic (giving off heat). For the roaster, this means that the beans are heating themselves and an adjustment of the roaster's heat source might be required. At the end of the roasting cycle, the roasted beans are dumped from the roasting chamber and cooled with forced air.
Once the beans have cooled down and before the next batch is nearly ready, the beans are put through a de-stoner that also traps metal objects as well as small stones. When you consider the origin of the beans it comes as no surprise that various foreign objects find their way into a bag and may cause damage to your grinder blades. After destoning the beans are then weighed, bagged and heat-sealed ready for delivery and finally to be enjoyed in a cup of coffee.