Roast Profile & Preference
Learning about coffee roasting is very adventurous. It's an old craft but much knowledge about it is anecdotal, some legendary handbooks have gone out of print ages ago while the available handbooks can be highly technical without giving any concrete pointers and the more "experts" you hear, the more it seems to become obvious that everyone is just groping in the dark, doing the best they can amidst elusive facts.
I watched an interesting video (see at the bottom of this blog). In it, Morton Münchow presents the results of a scientific research into preferred taste differences between several roast profiles using the same beans. A panel of 92 persons tasted samples (by cupping, I presume) from the coffee in a completely randomized manner. Each coffee was tasted three times but the members of the panel could never tell from any number or code what they could expect. There as an average trend of preference and there were members who agreed to that line remarkably closely, others deviated more.
I took a few screen snapshots to show what were the highlights for me.
One "reference roast" had a fairly normal roast color, a total roast time of 12 minutes, with 3 minutes development time after First Crack set in. Then there was a "light" roast with a very short development time, a "scorched" roast rushed to the same roast color as the "normal" one in just 6.5 minutes, a "dark" roast with a longer development time and higher end temp, an "underdeveloped" roast with 3 minutes development time and the same roast color as the "normal" one but a very long time before First Crack started and a "baked" variation with the same roast color and a development time of 6 minutes instead of 3 minutes, practically flatlining without any "Rate of Rise" in temperature towards the end. All done in a drum roaster (as indicated by the "dip" and "turning point" at the start of the roast, when the cool bean bass is charged into the hot roaster).
The test panel on average preferred the "normal" roast profile and to my surprise, the panel chose the "baked" one as second best with the ultra-fast roast as close third, the "underdeveloped" roast not very far behind and the "dark" and "light" ones trailing behind with the "light" one significantly failing.
To replicate the ultra-fast "scorched" profile, one needs a powerful fluid bed roaster or a small drum roaster with enough mass to accumulate lots of heat and the ability to transfer all that energy to the beans without too much harm, so I won't be looking at that much myself.
It seems to me that a "successful profile", a trajectory of time and temperature in a mass of beans that's being gently agitated, with a steady airflow blowing through the mass, could be scaled to happen in say 35% less time or even 35% more time than a fairly successful roast and still be acceptable/okay/fine. That would create a wide scope to search for the "sweet spot", the "best possible" roast with sweetness and a pleasant complexity of taste and aroma in beans that will keep up to a month after roasting.
In my view, the results of the test described in the video below suggest that looking to improve an already pleasant roast, one can safely risk "baking" by stretching the development phase while not raising the end temperature. This would comply with the advice given by Scott Rao to always have a declining Rate of Rise.
See also: http://artisan-roasterscope.blogspot.nl/2015/10/natural-roasts.html -- A blog by Marko Luther about "Natural roasts."
Morton Münchow himself will probably not agree with my interpretation of his results. In his conclusion, he suggests that the "baked" profile should not have been that successful and he explains that most of his colleagues, better schooled at tasting, would agree with him that "baked" coffee yields a distinct and unwanted taste. He would prefer to "calibrate the panel" in a new test, so primarily members who agree with his preference would take part in further research.
Together with Jan van der Weel, I will look further into a declining Rate of Rise and a development phase stretching up to 25% and a little beyond that of the total roast time, in the little PID controlled fluid bead roaster that I use.
Below is a recent profile. I would be looking to extend the last phase, not raising the end temp because I aso want a slightly lighter color (Tonino 95):
Also see Jan van der Weel's blog about Joanna Alm's presentation on roast profiles.
I watched an interesting video (see at the bottom of this blog). In it, Morton Münchow presents the results of a scientific research into preferred taste differences between several roast profiles using the same beans. A panel of 92 persons tasted samples (by cupping, I presume) from the coffee in a completely randomized manner. Each coffee was tasted three times but the members of the panel could never tell from any number or code what they could expect. There as an average trend of preference and there were members who agreed to that line remarkably closely, others deviated more.
I took a few screen snapshots to show what were the highlights for me.
One "reference roast" had a fairly normal roast color, a total roast time of 12 minutes, with 3 minutes development time after First Crack set in. Then there was a "light" roast with a very short development time, a "scorched" roast rushed to the same roast color as the "normal" one in just 6.5 minutes, a "dark" roast with a longer development time and higher end temp, an "underdeveloped" roast with 3 minutes development time and the same roast color as the "normal" one but a very long time before First Crack started and a "baked" variation with the same roast color and a development time of 6 minutes instead of 3 minutes, practically flatlining without any "Rate of Rise" in temperature towards the end. All done in a drum roaster (as indicated by the "dip" and "turning point" at the start of the roast, when the cool bean bass is charged into the hot roaster).
The test panel on average preferred the "normal" roast profile and to my surprise, the panel chose the "baked" one as second best with the ultra-fast roast as close third, the "underdeveloped" roast not very far behind and the "dark" and "light" ones trailing behind with the "light" one significantly failing.
To replicate the ultra-fast "scorched" profile, one needs a powerful fluid bed roaster or a small drum roaster with enough mass to accumulate lots of heat and the ability to transfer all that energy to the beans without too much harm, so I won't be looking at that much myself.
It seems to me that a "successful profile", a trajectory of time and temperature in a mass of beans that's being gently agitated, with a steady airflow blowing through the mass, could be scaled to happen in say 35% less time or even 35% more time than a fairly successful roast and still be acceptable/okay/fine. That would create a wide scope to search for the "sweet spot", the "best possible" roast with sweetness and a pleasant complexity of taste and aroma in beans that will keep up to a month after roasting.
In my view, the results of the test described in the video below suggest that looking to improve an already pleasant roast, one can safely risk "baking" by stretching the development phase while not raising the end temperature. This would comply with the advice given by Scott Rao to always have a declining Rate of Rise.
See also: http://artisan-roasterscope.blogspot.nl/2015/10/natural-roasts.html -- A blog by Marko Luther about "Natural roasts."
Morton Münchow himself will probably not agree with my interpretation of his results. In his conclusion, he suggests that the "baked" profile should not have been that successful and he explains that most of his colleagues, better schooled at tasting, would agree with him that "baked" coffee yields a distinct and unwanted taste. He would prefer to "calibrate the panel" in a new test, so primarily members who agree with his preference would take part in further research.
Together with Jan van der Weel, I will look further into a declining Rate of Rise and a development phase stretching up to 25% and a little beyond that of the total roast time, in the little PID controlled fluid bead roaster that I use.
Below is a recent profile. I would be looking to extend the last phase, not raising the end temp because I aso want a slightly lighter color (Tonino 95):
Also see Jan van der Weel's blog about Joanna Alm's presentation on roast profiles.
Below is the YouTube video I referred to:
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