Roasting Ka’u Coffee – The Roasting Process

We started with the Harvesting process, then Cherry Processing, then the Dry Milling process and finally we reach one of the most critical aspects of the entire operation, the roasting process.  Why the most critical? Because all of the work leading up to the roasting process can easily be ruined in seconds.

We operate with two top of the line Diedrich Roasters: IR12 (12 kilo/25 lbs capacity) used for custom roasts and small batches, and our work horse CR50 (50 kilo/100 lbs capacity) used for production roasting.  Both roasters are completely manual; meaning a skilled and experienced human is operating the machine, manipulating the batch and determining how the roast runs.


Roaster Skill
While precision and consistency are aided by the sophistication and craftsmanship of our equipment, our success is heavily dependent upon the experience of our roasters.  Our Chief roaster has 8 years of roasting experience and has completed several SCA (Specialty Coffee Association) roasting courses aimed at advancing a coffee roaster’s career towards the ultimate goal of becoming a Master Roaster.


Roasters preside over transformation of an unexceptional little seed into the complex, diverse, and delicious “beans” that we grind, brew, and enjoy. Even for very experienced roasters who may have been in the trade for years, the transformation that coffee undergoes in the roaster never stops being a source of fascination and excitement, especially if they are lucky enough to work with really great green coffee, as we do here at Ka’u Coffee Mill.



Science of Roasting
Although the process through which green coffee beans transform into roasted beans used to brew coffee is fairly simple, it is also quite easy to mess up. During the roasting process there is a combination of science and skill being applied.  The coffee must be brought to a specific internal temperature or level of “development” through the careful application of heat and close observation.  The roaster utilizes all of their senses including sight, smell and sound during the roast process.
Heat not only caramelizes sugars and browns the coffee during the roasting process, it also catalyzes a host of other chemical and physical changes that, when properly executed, create a product that is both familiar and surprising. Basically, roasting is the application of different types of heat to create chemical and physical changes in green coffee.


Here at Ka’u Coffee Mill, we believe the success and popularity of our coffee lies in the passion and love that goes into each and every batch.  We take great pride and care in producing our award winning coffee from seed to cup.







On a busy roasting day we typically roast up to 2000 lbs of coffee, depending on orders received and how busy our retail shop is.  Our coffee is fresh roasted every few days to provide our customers and wholesale clients with the freshest coffee possible.

The fresh roasted coffee is put into storage bins to de-gas for 24 hours and is then sent to the production area for bagging and order processing which will be a future blog topic.  Stay tuned!





Check out these cool videos showing the roasting process up close and personal