t o n x . o r g

After alot of trial and error, I am finally getting good results from the Probat Pre 1Z electric sample roaster.

Today I roasted six different Sumatran beans for cupping this week (Victrola’s drip blend will soon be 100% organic and one of these Sumatra samples I’ve roasted up today may become part of it). There is very little good information online about roasting on one these contraptions, so I’ll share a few notes here for posterity…

The Probat Pre 1Z and I had a rough begining to our relationship when I brought it home to start tackling a backlog of green coffee samples several months ago. Temperature readings from its thermometer didn’t correspond to the numbers I’d grown accustomed to on the Diedrich and its responsiveness when moving the power dial was mysterious. Early batches roasted far too quickly, hitting first crack in under 3 minutes and resulting in some foul tasting coffee. Some improvement came in selecting a better temperature to drop in the beans but I was still relying too much on fresh airflow to regulate the temperature and the resulting roast tasted thin and baked (furthering my suspicion that some of the hot air roasting methods popular with home roasters might result in flavor taints).

Phone calls and emails to some of our green bean brokers who use similar equipment turned up a few good pointers. Several pounds of old green coffee were used for some trial and error and eventually the parameters for a steady 8 to 12 minute roast emerged. An article in the recent issue of Roast by superstar coffee consultant Willem Boot (see link below) confirmed we were on the right track.

In a nutshell, the profile that seems to work well for me (for the four people on the planet who might find this useful) is preheating the drum to a stable 300f, dropping in the beans and bottoming out around 260f around the 2 minute mark. I climb slowly from this point (the dial moving from 4.5 towards 6), watching the bean for color changes and bring things up around 290, typically by 5 minutes. A steady climb of about 10 degrees a minute (the dial riding between 5.5 and 7.5) puts me at first crack around 320f or 7 minutes. The key after first crack is to continue to add energy, gaining temperature at a controlled rate without stalling the roast or speeding ahead too fast into 2nd crack. The airflow knob is kept relatively steady for the whole roast, opening up just enough for the smoke to vent and periodically to pull chaff from the drum earlier in the roast. Using the air flow to slow momentum seems to result in less impressive flavors in the final cup. [The caveat to all these numbers being that thermometers, while probably stable, are likely to vary from machine to machine and the environment certainly plays a big role. These numbers were arrived at roasting outdoors on a cool evening and in my kitchen with the window open on a zip-your-jacket afternoon.]

Willam Boot (BootCoffee.com) has a nice rant and some good pointers in his article The Struggle with Sample Roasting, available here as a pdf.

This entry was posted on Sunday, October 24th, 2004 at 6:20 pm and is filed under Coffee. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.