I've been roasting coffee for over 15 years, so just beginning to get the hang of it!
This is a methodology I've developed using my Gene Cafe roaster with a Lego Technic controller (Lego "borrowed" from son over a decade ago 😉).
For anyone interested, the main findings in my continued research into this slightly dark art are:-
☕ Depending on your roaster, you can only get heat into the beans at a given rate. Try to determine what this rate is and don't exceed it too much - aim to "pull" the beans to temperature.
☕ There are over 250 chemical reactions occurring during the roasting process. A lot happens around the Maillard reaction - between about 160 and 180 degrees C. I've found that pausing around this temperature allows the flavours to develop and results in a more even roast.
☕ The beans should all begin to crack around the same time (ideally). I start to reduce the temperature slowly after the first crack, then switch to the forced cooling mode usually around 30 seconds after the first crack, as that's my preferred roast level, and a good starting point for most beans.
Every roasting is an experiment, as no one has truly mastered the science 😉