Posted by: Andre | January 22, 2010

Achieving Predictable Roasts

Some weeks with the profiler has led me to a few conclusions about profiling roasts, how useful it is, and in general how to come up with new profiles and achieve old ones that worked. With my setup a simplistic approach (to heat adjustments) always turned out better. My 3 main roasting phases are:

  1. Drying (until about 100C)
  2. Roasting until First Crack
  3. Roasting between 1C and 2C

There is a couple periods in between, such as when heat adjustments are actually made, but my advice is to cup or taste your results and let them be your guide. The real-time computer graphing has allowed me to forget about the tedious parts of recording things every minute, but I’ve found that I still have to mark when I make heat adjustments and of how much.

  1. Drying Phase: This is the period up until about 100C and from what I understand it’s only purpose is to really get your coffee to a standard moisture content. I try to decide on this period and how fast it should be (the first time) by looking at how wet the green coffee is. Very little or no chemical changes are taking place
  2. Roasting to 1C: For many coffees, a gradual ramp to 1C works best, by incrementing the amount of heat until maximum (when at max roast load). I’ve found that larger jumps in heat do not produce results I like as much. Ideally this will result in a sort of concave curve going from the drying phase to 1C.
  3. Roasting to 2C: Here I try to level out the roast for around 30s after first crack, and then begin a 2-4C per minute slow ramp towards 2C at around 5 minutes from rolling first crack. During this period I’ve found it most important to just not let the graph dip.

Overall, exactly following a planned profile graph never seems to work. Adjustments should ideally be few and at key places, and deviating to meet up with a target line usually ends in disaster. So keeping my guidelines in mind I’ve been able to achieve predictable results, and many times very good results.

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