Getting the feel for the Corretto

[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

[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.

[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

[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.

[stuartgrant]

Re: Getting the feel for the Corretto

(Someone else please comment on this theory.)

Cant offer anything definitive, TG, but I have noticed that slower ramps to ~100C (ie. longer drying phases) tend to give a quieter first crack at a higher temperature in one experiment we did with Peru Ceja de Selva.

Secondly, before we had a thermocouple set up we had a few super slow ramps to first crack which resulted in little to no actual cracks.

As I said, nothing definitive, but both those observations back up what you theorised above...

Cheers
Stuart.

[Thundergod]

Re: Getting the feel for the Corretto

Maybe try drying them for a shorter period.
Say 2 minutes.
My understanding ids that the FC is the steam explosively escaping.
If youve dried the beans too much initially, they may not crack.
(Someone else please comment on this theory.)

Working without temp guidance is more difficult, but I did it when first moving up to a corretto and recently going back to a bowl.
Its not impossible though.

[Droshi]

Re: Getting the feel for the Corretto

Try 300g then.

Yep, tried 300g today, but I feel like Im shooting in the dark. Probably still better than nothing, but the roast was much longer than I feel like it should be.

I shoot for a ~3m drying phase, then somewhat rapidly try to ramp up to 1C. Backoff the heat gun to try to aim for a ~5m rest to 2nd crack.

Unfortunately without temp measurements and without being able to hear the cracks very well I cant do a whole lot else. To me it sounds as if not all the beans actually crack like Im used to hearing in the drum roaster...they all must, but I guess some are just quieter and cant be heard over the heat gun fan and beans stirring noises.

Ill report back again once I setup my makeshift DMM.

[Thundergod]

Re: Getting the feel for the Corretto

Im somewhat hesitant to bump up to 600g batches as thats a lot of coffee to mess up in one roast.

Try 300g then.

[Droshi]

Re: Getting the feel for the Corretto

I might try just tossing a thermocouple into the beans from the top and wiring it up to a DMM without temp readout. Just measuring resistance and using a conversion table should at least be better until the real datalogger gets here.

I feel there would be some benefit to a cover as well, but would probably need the DMM to make sure I dont overheat everything.

Im somewhat hesitant to bump up to 600g batches as thats a lot of coffee to mess up in one roast.

[greenman]

Re: Getting the feel for the Corretto

Once you get a thermocouple monitoring the bean mass life will become easier!!

[Pavoniboy]

Re: Getting the feel for the Corretto

I ended up covering the pan with a peice of wood so now that only about 1/3 of the pan is open, i get much better consistancy and can use a lower heat on the heat gun.

Hmmmm...maybe I should persist with relearning my roasting with a partial lid on.

[bolb]

Re: Getting the feel for the Corretto

I tried the removal of the window in the lid and yes the surrounding plastic started to melt with the heat.
I ended up covering the pan with a peice of wood so now that only about 1/3 of the pan is open, i get much better consistancy and can use a lower heat on the heat gun.

Mal

[Pavoniboy]

Re: Getting the feel for the Corretto

Ive seen a picture of someone that cut the window out of the lid on their bread machine and stuck the heatgun tip in insulated with aluminum foil. Any ideas there?

You dont have to cut it out on most BMs...when I first was setting up my corretto, I simply unscrewed the bottom of the lid from the top of the lid and slid out the glass window, and did it back up again (I had seen the heat gun through the window trick previously too).

HOWEVER, I also think it is a bad idea...I have never been game enough to try it...cant help but think I will start melting plastic somewhere along the line. So although the window is removed, I havent ever used it this way.

I, like others above, have a Breville with rectangular pan and always roast between 500 and 600g. This always works a treat for me with the BM open. I began experimenting with using a foil pie tray weighed down with a rock to partially cover the pan...but then realised this is just having to learn my roasting all over again when I already get great results so have reverted to simply using the open pan method.

[Droshi]

Re: Getting the feel for the Corretto

Hi Droshi, I have a Breville with rectangular bucket and I started doing 300g batches but have found as TG above has said  that 600g is the optimum batch size for my setup, I tried 800g but it was a tad uneven, 600g gives you 500g of roasted beans which fit nicely into the 500g zip-lock bag or 2x250g bags.
Ive found some beans have a very quiet first crack, a good indicator is watching the colour of your beans and getting close to first crack the smoke is a good sign you are almost there, same with second crack the smoke usually increases close to 2C plus most beans are quite audible, the DMM will make life a lot easier and give you control over your roasts. I start with the gun 3cm from top of the bucket and adjust it as the roast progresses aiming the gun into the corner of the bucket, the heat probe is located 2/3 the way up the bean mass. I reach 1c around 200C and 2c around 216-220C.
Enjoy your roasting

Thanks! This answered some of my above questions too. And seems to confirm that my roasting batch size is quite too small. I suppose it makes sense unless I have a way to enclose the unit much more with a lid or something.

Ive seen a picture of someone that cut the window out of the lid on their bread machine and stuck the heatgun tip in insulated with aluminum foil. Any ideas there? Seems like a bad idea, but maybe by pulling it out every now and then and with a DMM might not be.

[Droshi]

Re: Getting the feel for the Corretto

Sorry for the lack of info. My breadmaker is an old Regal model #K6728CE and heat gun is a newer Bosch PHG-600-3 (I believe it has heat settings of 50C, 400C and 600C according to manual with increase in airflow amounts as well).

First roast I attempted to vary the heat by switching between the two highest settings, 2nd roast I moved the tip further away to make it cooler and left it on the highest setting.

How close do you think I should have the tip? All the way inside the bowl? Maybe a cover as well? The main reason is because 1st crack didnt seem to be all that pronounced, in other words I only heard a few beans crack and it never really progressed into what I would call rolling crack unless most of the beans werent that loud and only a couple were.

Maybe higher batch sizes would solve my problems and once first crack hits the heat released would help even out temp and start other beans cracking. I would much prefer the smallest batch size and to just roast multiple times. That way I can try many different profiles without causing caffeine trauma.

I tasted both coffees this evening and they do taste good, and is mostly what I would expect from a Brazil. Not much high notes, but good body and great chocolate flavors. Ill try to keep a sample of each around to taste each day and see how it progresses. Still I think with a couple tweaks to my process I could really get more out of them.

Of course with the acquisition of a multimeter most of this guesswork will become non-existent I would imagine.

Thanks for all the tips!