I decided to stay a little lighter on the Rwanda Gkongoro Nyarusiza than I might have, based on some test roasts I did. I roasted pretty much full heat until the very beginning of 1st crack; average of 1:30 minutes, 403 f. Then I brought the flame down to the minimum amount I could to draw out the roast time and yet not too little to stall the roast. This is critical, because when coffee goes exothermic during 1st crack, you must be providing enough heat to the roast charge in order to keep things moving along. It makes sense in terms of pyrolysis in other types of cooking, and it makes sense in coffee. The key browning event in coffee is the Maillard reaction, an interaction between amino acids and reducing sugars, and it's the same that occurs in the browning of beef! And it definitely wouldn't be good BBQ technique to achieve a nice brown meat by letting it go cold when it's half done, then crank up the flame again and finish it. Anyway, the Probat takes care of warm-up phase with the roasts quite well - we don't have to diddle with the air and gas controls from the green-to-yellow-to-tan phases. We do make adjustments for the finish phases of roasting, and this is true with the Costa Rica La Libertad decaf this week, because you can easily race to the finish temp. of 428 f on this with too much "momentum". So I also back off the flame severely at the start of first ... in fact I make sure with decafs that I approach first gingerly. Classic Italian is our darkest roast for espresso, darker than Puro Scuro and Monkey and Moka Kadir. That said, we are still on the light side compared to other roasters. If you want shiny black pieces of carbon, look elsewhere. The fact is, we put such nice coffees in our blends, I just can't abuse them with roasting until everything tastes like charcoal. 463 f is the highest finish temperature on the Classic, and it does depend a little of the atmosphere and "speed" and which you approach 2nd crack. That's where you need the human in front of the roaster. In coffee, the numbers always DO lie, at least just a little bit. The thermocouple can shift a little, the air can be a little more humid, the gas valve can be set a tad more open or closed ... that's where an experienced roaster-person is so important.
Sweet Maria's Weblog
Things are starting to even out a little more with the heat on the Probat and our roast times are back in the 15-16 minute range, which is ideal for this Full City roast. Dry-process coffees tend to produce a wide range of color once roasted and this Golocha is a perfect example. There are a few quakers to cull out but leave the just slightly lighter beans in there to really enjoy the origin characteristics of this coffee. First crack came on around 402 degrees and final roast target temperature was 440 degrees.
this is pretty much the highest level of hand-sorting, when coffee is visually sorted at a desk, not a conveyor, and not just machine color-sorting. You see this a lot in Guatemala. In one day, a person might do just 50 Lbs. of green coffee. It's another of the behind-the-scenes tasks between the tree and the cup that is too often taken for granted.
When Tom re-cupped this Kimel peaberry he noticed that a Full City roast seemed more apropos than a lighter roast. Going a bit darker brings out the complex spice palate in this vibrant coffee, in fact, I totally forgot to change the label to reflect this reassessment, so my apologies. For today's roast we took each batch to 440 degrees and they timed out at about 14 minutes--first crack began at 402 degrees. The reason these batches finished a couple minutes faster than normal is: I cleaned the jets on the gas fired Probat and WOW did it make a difference. I'd become accustomed to roast times more in the 16-18 minute range and every so often Tom would say "we really should clean those burner jets soon, it'll make a big difference". The Probat has a basic layout of 26 gas jet burners that each have a flared tip, by unscrewing each of these I was able to thoroughly remove any build up of carbon that was blocking the pathway for the gas. Now it is running hotter than before and I had to monitor the heat level much more carefully to keep each batch in the same ballpark time-wise. It was a fun challenge and a good way to learn more skills to provide a quality roast for everyone to enjoy.