Measuring temperature of the cacao beans

[annazh]

Hi all

So, I've been reading all of the topics of Ask the Alchemist about roasting, and I got confused about the roast profile temperatures. As I understand now, the temperatures for all the phases of a profile are the temperatures of the cacao beans not the temperature in the drum roaster. I am using a drum coffee roaster like this one:


www.akaneks.com.tr/index.php?p=0

which shows the drum temperature and it can be adjusted.
However, I don't know if the temperature in the drum is the same as the bean temperature...so does anyone have idea how to make a roast profile based on the drum temp? And how is it related to the bean temperature? When the drum is 212F, that doesn't mean the bean is the same and is entering the development phase, right? Or maybe I have to measure the bean temperature, but what to use?

Thank you! I've been roasting and testing and it just doesn't seem right.

Many thanks,
Maria

[Ben]

Hi Maria. You are correct--the profile temperatures are the bean temperature. This is not the same as the drum temperature, which is just the temperature of the air in the drum (often referred to as environment temperature).

To really do profile roasting, you need to be able to measure the bean temperature. Basing it on drum temperature will not be very accurate. Generally, drum roasters like the one you're using have temperature probes for both bean and environment temps. From the pictures, it does look like the one that yours has will not get into the mass of beans so will only measure the environment temp.

The best thing to do would be to add a second temperature probe to your roaster. This would require drilling another hole into the front in a place where it would be completely immersed in the beans during roasting. On your roaster, my guess is that it would go close to the window.

[annazh]

Hi Ben,

Thank you for the answer. I asked the manufacturer, they told me the thermometer is supposed to measure both drum and bean temp. I am not so sure though, since it doesn't seem right that the temperature is always the same (for the bean and inside the drum). I don't really want to drill the roaster since it's quite new and I worry I will mess something up. Do you know about some other type of thermometers?
Thank you again!

[Ben]

One thermometer can't measure both the environment and bean temperature. To actually roast your beans, the environment temp has to be hotter than the bean temp, so those temps can't really ever be the same.

I can't think of another way to monitor the bean temperature without putting a thermometer into the mass of beans. It's possible that there's a way to snake a probe in without drilling through the front panel, but without actually having the roaster on hand to look at, I can't offer any suggestions.

Is there a metal shop in your area you could have do the drilling?

[Ben]

On a side note, this is the kind of probe I have bought in the past:

www.amazon.com/gp/product/B00899A4LY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I think they need a connector like this:

www.amazon.com/gp/product/B00CQML8UQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Also, I use this data logger on my test roaster. It has a USB connection that can be used to track your roasts on a computer using Artisan roasting software.

www.amazon.com/gp/product/B005GFHZLG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Artisan:
artisan-scope.org