Drum roasting

[krizzstroganof]

Hi, I'm new to this and trying to grasp all the information as i'm roasting and making my chocolate.
My roasts seems to take way too long compared to the information I find on the internet and compared to other peoples roasting profiles. 
I have a convection oven, heating from top and bottom, a drum that rotates...this should get me a nice and even roast.

After a couple of roast, having trouble getting the outer bean temperature up, I set the oven temperature to max (230 celsius). Roasted 15 minutes and the turned down to 200 celsius and continued roasting til a got an outer bean temperature of 132 celsius. This took 40 minutes.

What am I missing? Roasting at this temperature should get me to EOR much quicker I think. 
I tried roasting long and with low temperature and had big trouble getting over 100 celsius (outer bean temperature). 
My oven is new and should be powerful enough when I compared to what other people using and having good roasting results with. 

The drum can take around 1 kilo of beans, I have been roasting 800 grams. I think the beans have enough space to move around. Maybe I should try even less to let the beans move around even more? 

Cheers,

[Ben]

Hello.

I think a little more information on your roaster and roasting process would be helpful. Here's a few questions:

Are you familiar with roasting profiles? If not, definitely read the Ask The Alchemist posts on ChocolateAlchemy.com starting around ATA 200. They provide a ton of good information about roasting cacao.

How are you measuring the bean temperature?

Are you preheating the oven? If so, to what temperature? I've found with my DIY convection oven-based oven that I get a faster ramp up from initial bean temp to 212F/100C (end of drying phase) by preheating the oven to about 85% of my highest temperature before loading the beans. Then I reset the oven to my highest temperature (230C for you). This causes the oven to turn on the burners continuously until that higher oven temp is reached. This helps to speed up the initial phase of the roast.

What oven are you using, and how much power does it have?

How fast does the drum turn, and does it turn so that the beans are close to the convection fan, or farther away?

What temperature were the beans when you reduced the oven temperature? Was your decision to reduce the temperature just based on time, or was it based on bean temp? Really, all that matters is bean temp, so everything should be based on that.

How full is the drum? Would 1 kilo fill it completely? It should probably only be about 1/2 full at most.

-Ben

[krizzstroganof]

I've been reading John's post about drum roasting and I've been trying to copy as much as I can. My numbers don't fit with his information and time...so I most of course do something different. 

I have been preheating the oven because I read in one of John's post that the temperature will drop when loading the beans. So there is no worries beginning with high heat.
I haven't tried the 85% pre heating. Maybe that would give it a kick. 

I'm measuring temperature with an IR termometer. I've check so it reads properly. 
I did the drop of temperature because I was afraid of burning the bean but as you say it's all about the bean temperature so maybe I shouldn't be afraid of that in the future... but 230 celsius for 15 minutes, I should be close to EOR when comparing to others roasting profiles that using high heat. 

The power of the oven is 2000W. I have to measure the time it takes for the drum to rotate because at the moment I don't know. I would say the drum is pretty close to the heating element without being "dangerous" close. If you want a closer look you can visit: steba.com/product/baking/compact-bake-ovens/grill-and-bake-oven-kb-41/?lang=en
The drum will be full when filled with 1 kilo of beans. I will definitely try roasting with less bean next time. 

The chocolate I've made so far was good but I want it to be repeatable and like to use roasting profiles, it feels like I have the equipment and so the possibility to do that. Anyway thank you so much for your help. 

Cheers,

[mark]

If at all possible you should try to get a probe in the bean mass instead of using the IR through the glass. Once you have the probe in the bean mass and are confident you have a reliable bean temperature reading you may find you need to put less beans in your drum. It sounds like it might be too full.

[krizzstroganof]

Yeah I don't think the readings through the glass is right, it dosen't make any sense anyway. So I take the drum out super quick for the readings, I know this isn't optimal but I don't see it effecting the roast to much with the high temperature etc. 

I did a roast yesterday, starting at 200 celsius (85% of the max temp of oven) just like Ben suggested. Then i turned it up to max, checked after 13 min. The reading was 110-120 on different beans. At 25 min most beans where around 132 celsius, some 140 and some 120. I decided to end the roast then. The nibs tasted really good and is now in the melanger for refining. 
Also I only roasted 500g beans this time...it probably made a huge different. 

Today I'm doing a roast at 150 celsius and pulling the bean every third minute to see whats happening to them as the roast progress. This will be a very good learning experience I hope.  

A lot of people also speaking very good about low and long roasts so I did one of those, 135 celsius for 45 minutes. The bean temperature at the EOR was around 90 which seems way too low. Any thought on this? 
To me this doesn't make seems since the bean haven't gone through any flavour development etc...I have eaten really good chocolate made this way so there must be something to it. 

Cheers,

[Ben]

Completely agree with Mark. If possible, switch to a probe into the mass of beans. When you open the oven it loses a lot of heat and can take a while to return to temp. Pulling out the drum to take readings will definitely slow the roast down.

Glad to hear the more recent roasts went better when roasting less cacao. Interesting that you had a 20 degree variation between beans. One of the strengths of drum roasting is that everything gets roasted the same.

Low and slow is just one way of roasting. And, like all roasting techniques, works well for some beans and not so well for others. Different beans need different roasting profiles to bring out their best flavors. There is no universal best way to roast cacao. I'm currently working with 5 origins and only one of them benefits from a more gentle roast profile (and I wouldn't describe even that profile as 'low and slow').

[mark]

Opening the oven and taking the drum out is definitely leading to a lot of heat loss each time. Imagine doing that with a cake, a similar thing is happening with your beans.
I'm not sure if you've seen John's video on how to drill a hole in the side of the Behmor to get a probe in: www.youtube.com/watch?v=aT3ZFSfyex0

You could probably do the same with your oven.

[krizzstroganof]

Yeah I think your right. I will figure out how to get a probe in there, seems like the only way... Thanks for everything! 

Cheers,