Diy coffee roaster and first roasts!
Hey, so for a few months I have been building a diy fluid bed coffee roaster with my dad, based on a hot air pop corn machine. We are very close to the end and made a truly complex roaster for it being diy (I don't have pictures yet, we need to finish small details, but I'll do another post when it is 100% finished).
The roaster is controlled by a raspberry pi connected to a 7 inch touchscreen, my dad mostly coded the python software to controll everything (solid state relay controlling the heating element, pwm fan controller, Thermosensor for the pid controll... Everything!).
The whole roaster is build inside of a medium wood box, with a oak veneer (the roaster is missing the screen in the picture because the wood oil was curing.)
We are still missing a big chamber to put the beans in, but I already tested the roaster with the original chamber of the pop corn machine and wanted some feedback.
The green beans I used for my tests are Costa Rican Tarrazù washed beans. Since it was my first time roasting I followed a temperature profile someone posted online for Tarrazù beans. (https://www.roastetta.com/roasts/costa-rica-tarrazu-esp/)
I fired it up and at the end of the first roast (9.30 mins) using a very similar profile to this one the beans were barely roasted, still very golden and hadn't even reached first crack. So I fired the roaster up again manually and gave them an additional 10 minutes at 180 Celsius. At the end they had the color of very lightly roasted beans but I still am nut sure they reached first crack (I didn't know what to hear since it was my first roast). I found it weird that they were still so light after 19 mins of roasting and I think the issue was that my thermometer was to close to the got air exit, therefore measuring air temperature rather then beans temperature.
For the second roast I decided to put the thermometer higher up in the chamber since the got air is coming from underneath, to increase the temps a little and to shorten the whole roast to about 12.5 13 mins.
The temperature were somthink like :
200° charge
125° beginning of drying
135°
145°
155°
165°
185°
195°
200°
205°
215° maintaining this temp untill first crack and during the development (2 min 10-20s)
I used approximately 1 min per temperature section.
This worked much better and I really got to hear first crack.
Today I tried both, using my la pavoni professional, and I was actually pretty surprised by the coffee being not that bad. The first lighter roast was, as expected, on the acidic side and lacked of complexity. So I ended up doing a cappuccino with it which had a pretty fruity and sweet taste to it, I had never tasted that before In a cappuccino.
The second shot using the second roast was better, extracted smoothly and has still, a bit more acidity and bite than when I buy the same beans roasted by my local roaster. I don't know exactly how to describe it, I am no coffee tasting expert but it tasted like the coffee had a smaller range of flavors. Lacking a bit of depth and body in my opinion.
The picture are:
The wooden box of the roaster (missing the screen and the chamber in the picture)
The first roast and second roast side by side
What could I change to achieve a bit more complexity and a wider range of flavors with those beans, I am a complete newbie to this!