First off, please, if you would be so willing: https://www.youtube.com/watch?v=50JJZIKdj0s
To start, Happy Roasting, I hope you are enjoying your roaster, brewing some delicious coffee, mastering your cup one bean at a time. This thread, like roasting, is trying to break down the parts to make a delicious roasted coffee only to be ruined by brewing lol just kidding around, but I can’t help there. In my best attempt, I will try to simplify as much as I can, how I do some things; like approaching a new bean, using some different types of profiles and what I do when I’m not getting a roast I prefer. I’ll try to keep it broad and expansive for those who like light and dark but really this is just something I am still trying to figure out and what I say or believe is constantly evolving. In no way is my belief some concrete idea, I am always expecting to be wrong and I am sure there are things I will leave out. So hopefully, in time everything will be in order, or not, which will suck. But if you are expecting some magical coffee god to descend from the heavens with all the coffee answers, keep praying, my friends. I certainly do…into my glass of scotch. Also fore warning: to limit all the "i think"s and “i believe” etc etc, this whole thing is just that so…yea ok let’s begin.
If you can’t preheat, you’ll just have to roast a little longer…
Contrary to the title. It is really important to talk about the 5 main profiles first. The key factor is the main movement of these profiles are along the Z axis. This just means that…well why don’t I show you…
Having the middle of the curve along this axis/line is where the most significant difference of profiles will fall under. This line really affects everything from how much time you can spend in “dry” or the 1st and 2nd segments of the profile, how much momentum is being carried to first crack (which also effects the roast color and outside bean texture and evenness) and how that momentum dissipates (last segment) that either helps flavors develop or become lost.
The 4 Horsemen:
The fan in the “PNG Geometry” was terrible I highly don’t recommend.
Miss Cleo (90’s American TV show):
Charge: Helps with drying the beans, also introducing energy to really dense beans, it might be opposite for us air roasters then in a drum where more energy is needed in the beginning for denser beans than less dense. When I’m able to get nice fruit on a Ethiopian it’s by not pushing the charge/dry too hard. Fan is a magnifier for the temperature profile so as you increase fan speed you are increasing the strength of the temperature at that point. Hence why a high fan at the end can overly dry the beans and a low fan in the beginning can keep moisture like Tony Quiero stated in the SCA panel (he was only talking about the low fan in the beginning to keep moisture) (https://www.youtube.com/watch?v=MxiNW1d4bos, a very good listen I highly recommend taking the time for it).
Dry: Setting up the momentum into the “yellow to brown” segment, extending this in the 320F to 360F-380*F really gives an aroma not quite like anything else but exactly like it Transitioning from a slow dry to a fast yellow is ok but I have not had good results doing the opposite. Practice understanding yellow to brown by making caramel at home. This is the exact same concept. The McGee has talked about Millard and Caramelization at The Harvard as well.
Yellow to Brown: This is a tricky phase, it’s the start of the flavor chain and is the most important for getting a drinkable roast. To slow and thing bake off but also you will get into the marshmallow/vanilla area and also mesquite bbq wood. Too fast and you will get so much acid that you will create a black hole in your mouth. If you are lucky enough to pace this phase just right, you might be able to smell (very easily/shockingly) fruits, real distinct fruit notes. So far I have been solicited by blueberries, jackfruit, passion-fruit and blackberry. In the sense that I was doing something else and the smell smacked me in the face. But I have no idea how to get it. The faster through Millard/Carmelization, the less body and more ‘acid’ like notes, each profile requires balance, and by tasting after the roast you can determine where to move the profile. But when you move one part you have to move the others, or maybe know that you will have to lengthen or shorten the time you drop after your start of 1C.
Development: On a good profile it is easy to smell the development, from green/veg notes (increase end temp of yellow to brown, but you might/probably have to lengthen/shorten the Y/B phase but can keep the charge/dry/green, start with 15-30s movements), if your momentum/speed/slope is too slow in development. But if your development is fast enough (15-20ish*F/min not a lot of experience playing with this rate) those green notes will transition to something worthy.
Try the other profiles first and see what does what. This is the most important to understanding everything. Keep the fan at 80% with a 2 min cooldown. Seeing which profile get’s you close to what you like. If you like darker notes, lengthen the roast towards the end (12min) , Energy applied in the roast profile is like a see-saw. A darker roast might use a lower charge and dry temp to keep some moisture/flavors for the end to be developed for longer roasts. For lighter and darker, the charge and dry aren’t going to develop flavors but contribute to how the flavors will be developed, the job of yellow/Millard/caramelization is for flavor development. Charge and Dry are used to get the ball rolling and get the party started. If you are not getting the flavor you want in development you have to play with the Y/M/C and the dry/charge, if you found the flavor and want to keep it then you should tweak the back end of the roast, to either shorten the timing or speed it up to develop those green notes. If this sounds like you can affect the roast from both end, that’s because you can.but bigger movements are in the front and smaller ones are in the back (end).