Our Probat L-12: Probat thermocouples and temperature monitoring:
We measure this with 2 probes, simple bead type k-probes, one about 3 o’clock and one about 6 o’clock. I also have a probe wired for exit air temperature in a duct in the back, and that is the best way to measure environment temp, but i don’t refer to it often. The big, stock dial thermometer on the front of the machine measures environment too. We basically use it only to indicate drop temperature to start roasting, and for cooldown, to indicate when it is safe to shut the roaster off.
Temperature measurements in different roast systems can yield very different results, but if the measurement device performs consistently in your machine (be it a Hearthware, BehmorA popular electric drum roaster designed for home use, with variable batch sizes (from 1/4 pound to 1 pound) and a smoke-reduction system. It has been modified and..., Diedrich or what-have-you), then you can transcribe findings into something meaningful on your roaster.
In a perfect world we would all have calibrated devices that would measure internal bean temperature, not simply a probe that touches the outside of the beans as they tumble. Most probes are going to measure environment temperatureThe temperature of the roasting environment determines the specific types of chemical reactions that occur. There is a window of temperatures that produce favorable reactions for the ideal..., and even if they physically probe the coffee it’s going to be a mix of measurement, bean surface and environment.
So you always have to interpret and translate someone else’s numbers to apply to your roast system. One way is to compare 1st crackAn audible popping sound heard during roasting. In coffee, one refers to "first crack" and "second crack," which come from two different classes of chemical reactions.: An audible... temperatures. When do you hear the very initial pops of 1st? On the Probat it is between 402-405 farenheit. (Occasionally we have in initial signs of 1st crack as low as 395 f).
-Tom
