Finishing 2017 Guatemala Las Delicias

(I will be adding this to the earlier blog about roasting Las Delicias)

Las Delicias, Batch 40, DT at start of roast 177ºC, Tonino value after roast #94,
weight loss of beans 17%, moisture in roasted beans 4.3%, date 28 november,

Wrapping up this year's roasting of Guatemala Las Delicias beans from the farm of Manolo Muralles. Batch #40 was done today, finishing off what I had. 40 x 1.25kg in, 1kg+ out.

Batch #29 was done with the probe in the machine while warming up but after that one I kept the BT probe out and inserted it at the same time as charging the beans into the roaster so then the BT probe can be expected to more closely and realistically tracking the actual Beat Temperature.

Of course the BT probe basically just measures the perceived temperature at its insertion point, influenced by the speed of the rolling mass of beans that is twirling around the probe, also influenced by the air flowing in from the low front of the drum space, mixing with the bean mass and leaving through holes in the drum towards the exit ET point high up in the back of the drum chamber, and also influenced by the intensity of the heating elements as it heats up the drum metal mass, radiating heat towards the probe and the hot air from between the elements and the drum being drawn out and upwards by the airflow.

Towards the end of the roasts for this bean I more and more settled on this routine:

1) Switch on machine and Artisan. Make sure BT probe is out. Click on Drum and Airflow activation buttons in Artisan screen. Set Drum speed slider on 20 (38 RPM), keep Airflow slider on 0 (33% of max speed), click MV ON in Artisan to set heater on manual slider control, sliding heat to 99%, Sliding SV-DT for maximum allowed Drum Temp to 93 (176.7ºC), sliding SV to max (230ºC).

2) Setting a timer to 12 minutes.

3) After 12 minutes of warmup time, DT is nearing its maximum. When max DT temp is reached, SV-DT triggers the machine controls to shut off all 3 elements with a loud CLUNK so this cannot be missed and it ensures nothing goes out of hand here. I click on START in Artisan as soon as this temperature is reached.

4) I promptly charge beans, insert BT probe, click CHARGE in Artisan.

5) Artisan sets Air Speed to 20 (46% capacity) and I watch the start of the roast profile. If all goes exactly like the background target roast, I let things roll on according to the Alarms settings, if the green beans were a little colder that expected or room temp started out cooler then I temporarily lower Air Flow and observe the profile.

6) Stepwise, Artisan increases air flow according to the Alarms settings. A few minutes ahead of expected FC, Artisan also lowers energy for the three heating elements, to 90 on the slider (about 96% capacity and 80 on the slider (about 92% capacity). Responding to any deviations from the plan, I change air flow.

7) A little before FC is audible, BT tends to veer upwards and I check that air flow compensates this so the sudden exhale of energy from the beans won't rush the roasting profile towards its planned maximum temperature, while avoiding to let BT sag. Beans must go through this turbulent 'development phase' and the general attitude towards the beans must be to drive them carefully, keeping up the pressure (Rate of Rise above 3ºC/min) in a gentle and controlled manner.

8) I look for an AUC of 400 (specific for my roaster, and my probe locations so not directly transportable to another roaster) and and end BT of 207, also for a development phase of around 25% of total roast but that latter checkpoint weighs less in my decisions towards the end than trhe other two. If for some reason or other the roast curve was more aggressive than the background target and the BT reaches 207ºC faster, I can stop the roast earlier.

9) Cooling: the first seconds are most important, stopping the roast. I stir the bean mass with a wooden spoon and I stop the cooling fan when the beans still feel quite hot to the touch but not burning my skin.

10) I weigh the roasted beans, take a sample, cooling it by the open window, measuring its moisture percentage using the WILE coffee device, then measuring the roast color using the Tonino device. Weight, moisture and color info is added to the roast data in Artisan. I add the most relevant info in the title of the roast: bean, batch, starting DT, Tonino value, weight loss, roasted moisture value, date. Below the profile is listed, between other info, the AUC.

Batch 29 with BT probe in during warmup

Batch 38

Batch 39
Thanks to Manolo Muralles for these fantastic beans and thanks to Marko Luther for all his innovative work on Artisan, on the Tonino, on originally modifying the FZ-94 roaster and more. And thanks to Arnoud at Hoofdkwartier for selling me these beans! Also much thanks to Tije who helped implement the modification to regulate heater intensity.


Bob zei…
Wow Frans, this must be one of your most detailed blogs ever! Thanks for sharing.