A short introduction to the theory and practice of profile roasting.(coffee roasting techniques)

The merits of profile roasting occasionally come up in conversation; you may be interested in knowing more, but don't know where to start. Most information about profile roasting comes from people who roast on small shop roasting machines that have atmospheric burners with manual controls. Usually, they roast by clues of development supplied by the audible sound of the beans as they transit first and second crack temperatures. In this case, the roastmaster controls the heat input by making manual burner flame adjustments between high and low settings, while monitoring both the bean temperature and exhaust air temperature.

Large commercial roasting companies have computer controlled roasting machines that monitor several temperatures throughout the roasting process and the toastmaster has the ability to program the machine to make automatic temperature changes at various points during the bean development. The basic computer for making these automatic burner adjustment changes is called the Programmable Logic Controller, or PLC.

Basic training in using a PLC to make burner-setting changes is available from many of the manufacturers. in the simplest case, the PLC controls an atmospheric burner by modulation; switching the burner from low fire to high fire and back to maintain an average set point temperature. For coffee roasting, the PLC normally monitors two temperature points critical to roast control: bean temperature and roast air temperature. As the roast progresses and the bean temperature raises, the burner changes settings in response to the set points installed in the controller. These set points establish the roast profile.

Regardless of the size of the roasting machine, profiling the heat input is paramount to development of more favorable taste characteristics in coffee.

Controllers with touch screens are standard equipment on many new machines marketed today. The smallest roaster I know of with an "industrial burner" and a PLC controller is the Loring half-bag machine out of California. Of the larger systems, I'm impressed with the Scolari roasters out of Milan yet I roast on the Jabez Burns 23R..

As your company grows and you are forced to move up to larger equipment you will probably be upgrading to a system that has better potential for precise roasting heat control. On the other hand, if your equipment is sized correctly but slow, it may be possible to produce more and better coffee from your existing equipment by simply upgrading the control system itself.

Temperature Control

Precise roaster heat control is what gives a roastmaster the ability to practice his art of producing the optimal product.

Temperature control in any heat-processed …