Getting the feel for the Corretto

[stuartgrant]

Re: Getting the feel for the Corretto

Hi Droshi,

We recently "upgraded" to the DMM and datalogger on our Corretto. I use the inverted commas not because doing so was a bad idea... but Ive been reflecting lately on how much less effort/stress it used to be when we simply pointed the heat gun at the beans and "made them brown" in about 15 minutes!

Obviously, every improvement weve made to our Corretto has been intended to yield better roasts (more even, more consistent, more controllable, less tipping/scorching... not to mention better tasting), but it strikes me that every addition we make to the roaster is only as good as we are at using it to improve our roasts! In other words, you dont NEED any of the gadgetry available as long as youre paying attention, keeping notes, cupping the results and making improvements where necessary.

Having said that, the DMM and datalogger are a wonderful tool... but having 0.1C accuracy does tend to show up any problems you have in even temperature delivery. Kinda like having a naked group handle shows up any problems you have in dosing...


Philosophy aside, in regards to your roast profile, I have an inkling that a "soak" or drying stage is not really necessary in a Corretto for two (possible) reasons. Firstly, drum roasters store a lot of heat in the drum metal and I think that when pro-roasters talk about the "soak" stage (ie. 2-3 mins of low heat-input), the reality is that the beans are still heating up significantly from the large amount of heat stored up in the drum. Correttos dont store a lot of heat in the bread pan in my experience of doing back-to-back roasts so they probably need higher initial heat input.

Secondly, I suspect the airflow in a Corretto setup is higher than in a drum roaster, meaning that any drying stage in a Corretto setup may be liable to dry the beans out too much by the end of the roast resulting in tipping/scorching or uneven roasting.

Again, these are just theories, albeit theories based on 250 roasts :P. Im open to any comments people might have on the above!
Cheers
Stuart.

[Corretto]

Re: Getting the feel for the Corretto

Hi all,

Ive just got all setup and rewired the bread machine and roasted 2 batches of 150g Brazil Cerrado. Coming from a drum roaster things are a bit different. Mainly I didnt hear first and second crack really pick up into rolling, I only seemed to hear a few of the loudest cracks. Is that normal over the bread machine motor and heat gun blower?

I dont have a thermocouple and DMM yet, but I plan to get one when they come in stock here. Question is, until then Im wondering how I get a feel for more when things happen. Maybe I should keep the tip of the heat gun constant after the drying phase just to see what sort of profile Id achieve with that and then modify from there. How far away should the heat gun be when ramping up to first crack? Where should it be aimed? Ive been keeping it maybe 2-3cm from the top and angled to hit the beans and side of the bowl equally.

I was also thinking afterwards that my 150g might be a bit too low? Whats the minimum roast size people do in these?

Ill report back after Ive tasted these batches.

I thought I read quite a bit before starting, but now afterwards so many questions. Sorry if they are repeats.

Thanks!

Hi Droshi

Just a few thoughts and observations from a few hundred roasts:

Ive been on my second BM for a year or so now - a Breville BB250 with a square pan.  Have found this to produce much better (even) roasts than my original rectangular pan BM.

Without doubt the optimum size roast is 600 grams.  300 g is okay and 150 g is decidedly dodgy (and much much noisier) .

Ive found the tip of the HG should be level with the rim of the pan.  This allows for best control of temps.

Definitely get a thermocouple.  Although after youve been roasting a while you should be able to tell from sight and smell when FC and SC is about to commence.  I believe that roasting is 1/2 science and 1/2 art  

Regarding the lid argument, Ive tried putting a clear saucepan lid over the top of the pan and it does increase roast teamps dramatically, but for the most part isnt necessary (unless you live in the Antarctic) or is very windy and cold.

Regarding a drying out period - Ive found it doesnt really make much difference to taste, but no doubt some will argue against this.  I have found that a slow ramp up time to FC (at say 10 - 11 mins) gives less tipping than the quick ramp up method with a tapering off of temp before FC.

Oh and you cant beat a top quality HG too  

Belinda

[Droshi]

Re: Getting the feel for the Corretto

Ive recently dug up a PT1000 RTD, but unfortunately I dont have the proper spec sheet for it. I think for the most part their response is somewhat standard as compared to NTC type thermistors, so Im going to try using a conversion table and "calibrate" using 0C ice water and 100C boiling water to make sure my values are correct. From there it should be a simple matter of converting what the multimeter says (1194 ohms for example to 50C). The main reason for this is that I have a standard multimeter but not one designed for temperature yet. The probe I have should be good up to at least 300C, but many types are good up to 600-800C...unfortunately I dont know for sure, but since its just a spare I dont mind finding out

My plan is to just sink the probe into the level of the beans from the top to avoid drilling any holes for now. The main reason for that is because this probe is much larger in diameter as compared to the one Ill be getting with data logging feature, so Id rather make a permanent modification with my final equipment. Probably wont be as stable is a complete fixed point, but should be better than roasting by eye.

Onto profiles...I think it makes a lot of sense to assume that my drying phase is too long if Im not hearing 1st crack very well. From memory I believe at first crack the bean wall changes rapidly in structure which then releases most of the remaining water as steam which produces the sound. So not much water left, not much noise, which also means reactions later between 1st and 2nd crack will be starved for water (based on my understanding of the chemical processes happening).

Ive seen some discussion on profiles around here relating to a "soak" or slight rest time between drying and 1C. I was thinking a reduced temperature starting out and staying constant until around 150C and then a quick burst to 1C. If the HG is kept constant until 150C it should still produce a pretty quick temperature change initially but become slower as it reaches 150C. Then once more heat is added it will take a bit of time to start ramping up, which should produce that "soak" effect in between the drying and 1C. At least thats the theory Ill try to produce on the next roast.

So far the roasts have come out decent tasting, which is quite surprising to me considering the mistakes Ive made. And also considering I was just roasting by eye.

Still 600g for me is a large amount of coffee to make a mistake on, and even if I dont make mistakes (haha!) it still means that roasting several profiles and being able to use up all that coffee is pretty much impossible unless I start selling coffee. I was really hoping 150g would work, but I feel its too dodgy as well. 300g mixes much better in my machine, and Im sure I could do up to 600g as well, but for now until I get the datalogger and profiles for each bean type Im happy with, I think Ill stick with 300g batch sizes.

Great input from everyone, I think my setup is coming together well.

[bolb]

Re: Getting the feel for the Corretto

Dont forget that if you start with 600gm of green then you will end up with about 500gm of roasted coffee as on average you will loose 16 - 17% of weight during the roast.
My BM will do 300 to 600gm easily but i have found that 500gm is the optimum batch size for me to ensure a consistent roast result.

Mal

[Corretto]

Re: Getting the feel for the Corretto

Onto profiles...I think it makes a lot of sense to assume that my drying phase is too long if Im not hearing 1st crack very well. From memory I believe at first crack the bean wall changes rapidly in structure which then releases most of the remaining water as steam which produces the sound. So not much water left, not much noise, which also means reactions later between 1st and 2nd crack will be starved for water (based on my understanding of the chemical processes happening).



Still 600g for me is a large amount of coffee to make a mistake on, and even if I dont make mistakes (haha!) it still means that roasting several profiles and being able to use up all that coffee is pretty much impossible unless I start selling coffee. I was really hoping 150g would work, but I feel its too dodgy as well. 300g mixes much better in my machine, and Im sure I could do up to 600g as well, but for now until I get the datalogger and profiles for each bean type Im happy with, I think Ill stick with 300g batch sizes.

Dont forget that with small batch sizes the beans are thrown around a lot more and that makes it hard to hear the cracks. I find that small roasts - below 300 g - the cracks hard to hear.

BTW you learn more from your mistakes than you do from your successes 8-)


Belinda

[Droshi]

Re: Getting the feel for the Corretto

BTW you learn more from your mistakes than you do from your successes  8-)
Belinda

Very true. I roasted 300g Ethiopian Sidamo today with my makeshift temp probe. The temp probe seemed to work well. 1C & 2C happened as expected. Unfortunately the roast turned out horribly uneven. Im not really sure what I did wrong as I followed the profile in the Excel sheet in the tips/tricks board on roasting. Was similar to what I did before except just a bit faster up to 1C. I also found out that my HG cuts out when you put it too close. Maybe that was the reason for the uneven roast? I dont really think so, maybe it was the HG being closer than I had it before, or maybe its just the beans...or maybe I have no idea. Reports to follow on their taste (Im brave).

Pictures and graph attached.

[Droshi]

Re: Getting the feel for the Corretto

And the graph.

1C was actually at 14m.

[Droshi]

Re: Getting the feel for the Corretto

Also in retrospect, the picture looks worse as far as the dark levels go (sorry was taken on camera phone). The lightest parts are about right, but the darkest are lighter if that makes any sense. Still shows the clinging chaff (comes off if rubbed) and the uneven color.

[edit] Preliminary taste testing (as drip...not my forte in brewing methods, but eh...I really should keep a press pot around for this purpose) indicates it may not have been such a flop after all. Maybe its just how this bean roasts. Still looking at them I cant help but think theres no way it was done anywhere close to correctly.

Sorry not much for describing flavors yet, a couple not too good bitter notes, but I cant really say if they are roast defects or bean defects or brewing problems. I hope the latter, but most likely all!

[greenman]

Re: Getting the feel for the Corretto

The Ethiopians always roast a bit unevenly, every time I do a 3 bean pre-blend I can pick the Ethipians after roasting!!

[cuppacoffee]

Re: Getting the feel for the Corretto

The Ethiopians always roast a bit unevenly

I would agree that the Sidamo from the recent BeanBay roasts unevenly. I disagree that all Ethiopians roast unevenly.

[bolb]

Re: Getting the feel for the Corretto

1C. I also found out that my HG cuts out when you put it too close

Do you have a fan blowing over the top of the BM?
This will help cool the HG so it doesnt cut out and will also disperse the chaff during roasting.

[Thundergod]

Re: Getting the feel for the Corretto

My plan is to just sink the probe into the level of the beans from the top to avoid drilling any holes for now. The main reason for that is because this probe is much larger in diameter as compared to the one Ill be getting with data logging feature, so Id rather make a permanent modification with my final equipment. Probably wont be as stable is a complete fixed point, but should be better than roasting by eye.

I did this initially.
Try attach the probe to something solid like the handle of a wooden spoon. One version I had ran through a broken aerial tube.
The tube or spoon can then be fixed to the BM or bowl and this keeps it stable.
I tied mine to the bread pan handle with wire; no holes, fully reversible.

[Droshi]

Re: Getting the feel for the Corretto

The Ethiopians always roast a bit unevenly, every time I do a 3 bean pre-blend I can pick the Ethipians after roasting!!

As uneven as shown there? I guess I cant remember roasting this bean as SO before to compare so maybe its ok.

Do you have a fan blowing over the top of the BM?
This will help cool the HG so it doesnt cut out and will also disperse the chaff during roasting.

Nope, only a fan after the roast to cool beans. Ill have to find another outlet and try this. As a side note, I have my HG and BM plugged into the same outlet, Im thinking maybe I should get them on a separate circuit. I havent really had problems, but I just dont like the idea.

I did this initially.
Try attach the  probe to something solid like the handle of a wooden spoon. One version I had ran through a broken aerial tube.
The tube or spoon can then be fixed to the BM or bowl and this keeps it stable.
I tied mine to the bread pan handle with wire; no holes, fully reversible.

Good idea, the probe did start flopping around a bit towards the end of the roast, but I had the wire jammed into the handle and it stayed put decently well. Ill try this out for sure next roast, should make the temp readings more meaningful.

[bolb]

Re: Getting the feel for the Corretto

Nope, only a fan after the roast to cool beans. Ill have to find another outlet and try this. As a side note, I have my HG and BM plugged into the same outlet, Im thinking maybe I should get them on a separate circuit. I havent really had problems, but I just dont like the idea.

I have all mine on the same outlet and no issue at all.

[WSullivan]

Re: Getting the feel for the Corretto

ive got it all on a single phase too, no issues, wouldnt imagine the heat gun would pull too close to ten amps after startup, and the BM would use next to nothing without the heating element on either.