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  • Optimising Popper Roasting

    Hmmm,

    When I was using the popper as the primary roasting device, I used to do all my roasts with a t/couple immersed in the bean mass about 30-40mm from the bottom of the chamber. Then, by tilting the popper over away from the vertical, it is possible to make coarse adjustments to the roasting temperature... and of course by varying the batch size initially to get you in the ballpark.

    By managing the roasts this way, it was possible to roast up to 150g per batch and maintain reasonable control over the roast profile so as to avoid "blasting" the beans along too quickly. You need to have a tall chimney fitted to avoid bean loss but the extra control provided means you can tailor roasts to suit bean varieties and batch sizes, etc. Without a t/couple and a temperature reading DMM it would be a bit hit and miss but still maybe worth a try? :-?

    Cheers,
    Mal.

  • #2
    Re: simple smooth blend

    Well - I have (several) temperature measuring devices. Have been using a bead thermocouple submerged in the beans to check on the temperatures.

    Im not totally convinced about a few things:

    (1) The temperature measurement is the air, not the beans. Some "rule of thumb" adjustment to the measured temperature is possible, but it is still pretty crude.

    (2) Tilting the popper does affect the roast-rate. In my case, I reckon it accelerates the process!

    (3) Poppers seem to be a plausible answer, but the control just isnt there!

    Im thinking I might invest in one of those little rotisserie ovens, seems to me the temperature control in one of those could be simply measured. My problem is I only do small batches - 200g or so per week is enough. The popper would be nice, if only I could figure out a method of accurately controlling the heat - and measuring it!

    As far as the rate-of-heat-input goes and the beans "cracking early" - I think that might be part of the answer too - the beans have divots in them. Clearly some localised heating is popping off chunks!

    /Kevin

    Comment


    • #3
      Re: simple smooth blend

      Having tried popper, rotisserie oven and Corretto/breadmaker roasting. I would have to recommend the Corretto. I found the rotisserie oven did not provide adequate power unless modified. Another advantage of the Corretto is that you can clearly hear, see and smell what is going on. Your roasts improve really fast

      Batch size is up to you I have had good results from 100g - 500g

      Comment


      • #4
        Re: simple smooth blend

        Well KJM,

        I guess there must be enough differences between poppers that the techniques that work for some wont work for others :-?. The poppers I have are both Mistral units and do NOT roast identically if left alone, but the measures I mentioned above work for both of them despite their differing characteristics. Never had a roast batch accelerate when the popper is tilted over, slows it down every time.

        And yes, no matter which roast method you use the t/couple bead is going to be measuring the air temperature of the interstitial spaces between the beans but that is about as good as you can get it with a small bead t/c. A contact tab/probe type of t/c would probably be better as that would average the contact temperature of the beans over a slightly longer period, which when roasting, is probably preferable anyway. Unfortunately, I dont have a t/c of that type and I dont think the error is significant enough anyway to warrant my obtaining one. When its all said and done, measurements such as this are really only of use to the individual roaster (person) for future reference as they are definitely intrinsic to their particular roasting method, style and whatever else might creep into the picture affecting roast outcomes.

        Cheers,
        Mal.

        Comment


        • #5
          Re: simple smooth blend

          Well Mal, my popper is a Black and Decker (a hand-me-down from hazbean who now uses his I-roast pretty exclusively...). It does a fair job, but the heating profile is pretty much "light blue touch paper and stand clear"!

          This is getting a bit off-topic, but hey! Before doing some real work today, I tried checking the bean-mass temp of a sacraficial roast. My non-contact thermometer said 130C, the bead and the probe T/C both said 130C but the bead in the popper said 170C (just prior to switching it off). 40C is a big differential!

          Im an engineer/scientist type and Id dearly love to (slightly) automate the roasting process so I can at least reliably repeat a roast. Im kind of happy to bum along like Im doing now, watching, measuring and tinkering. But Id really like to nail the process!

          dkelly60 - Im not afraid of modifying electrical kit I was just thinking that a modified rotisserie oven doofer would be the closest home-brew approximation to a commercial whacking-big drum roaster. And so the roast profiles etc etc would be a close match. Your comment on the corretto sounds like I should look at hijacking the bread machine when the Chief Financial Officer is at work..... Hmmm...

          Anyway, back to topic: now have Columbians * 2 and Harrar *2 (and Sidamo *2) at darker and lighter roast levels. So that looks like 8 combos. I limit myself to 2 espresso/day. So this looks like a full week or so of experimental sipping.... Strewth! Coffee research is painstaking!

          /Kevin

          Comment


          • #6
            Re: simple smooth blend

            Gday Kevin,

            Yes, my background is in electrical engineering more so in the field than in a lab but that was my preference . Ive got a couple of immersion type t/c probes for my old Fluke DMM but that is packed away at the moment so have been using a throw-away DSE unit for monitoring roasts et al. I havent noticed the disparity you have observed though while I still had access to the Fluke Kit, the DSE t/c DMM averaged within +/- 2.0C compared to the calibrated Fluke Probe, so didnt really see the need to keep dragging the Fluke out of storage for this sort of duty, and besides, if I drop the DSE unit and break it, its not much of a loss, wouldnt want that happening with the Flukes though.

            Have gotta say though, roasting with a Corretto is a whole different ballgame to using poppers and I would never go back short of the BM biting the dust. The amount of control available is terrific and because of the "open" style of roasting that it is, observation of the beans roast progression is second to none. From an automation/control point of view though, a rotisserie oven would be a simpler proposition. Which ever direction you end up going though, its all good (as they say)... cant beat freshly roasted coffee at home 8-),

            Mal.

            Comment


            • #7
              Re: simple smooth blend

              Originally posted by Mal link=1181111390/0#13 date=1181551442
              Gday Kevin,

              Yes, my background is in electrical engineering more so in the field than in a lab but that was my preference . Ive got a couple of immersion type t/c probes for my old Fluke DMM but that is packed away at the moment so have been using a throw-away DSE unit for monitoring roasts et al. I havent noticed the disparity you have observed though while I still had access to the Fluke Kit, the DSE t/c DMM averaged within +/- 2.0C compared to the calibrated Fluke Probe, so didnt really see the need to keep dragging the Fluke out of storage for this sort of duty, and besides, if I drop the DSE unit and break it, its not much of a loss, wouldnt want that happening with the Flukes though.
              The disparity was the temperature of the beans - stop the heat and stuff the beans into an insulated cup with thermometer - versus the measured in popper temperature. The differential is huge (of course). When you start the popper, the measured temperature rises pretty quickly, but the beans arent that hot. Towards the end-point, the beans and the air get closer. Thats what I was trying to get at.

              I was never fortunate enough to buy a Fluke.... My meters are all knock off copies 8-)

              Originally posted by Mal link=1181111390/0#13 date=1181551442
              Have gotta say though, roasting with a Corretto is a whole different ballgame to using poppers and I would never go back short of the BM biting the dust. The amount of control available is terrific and because of the "open" style of roasting that it is, observation of the beans roast progression is second to none. From an automation/control point of view though, a rotisserie oven would be a simpler proposition. Which ever direction you end up going though, its all good (as they say)... cant beat freshly roasted coffee at home 8-),

              Mal.
              OK, so one question: how do you abscond with the bread machine and still retain the full set of male reproductive parts??

              /Kevin

              Comment


              • #8
                Re: simple smooth blend

                Originally posted by KJM link=1181111390/0#14 date=1181561964
                OK, so one question: how do you abscond with the bread machine and still retain the full set of male reproductive parts??

                /Kevin
                Ah well,

                I was lucky there, the Breville BM we have is very straight forward to bypass the factory control, so the unit still retains the capacity to operate as a BM when the need arises.... also helps that I am the baker in our household too

                Mal.

                Comment


                • #9
                  Re: Optimising Popper Roasting

                  OK, there has been a big delay in me posting the results of the "taste test" of the various roasts. So here goes:

                  (1) The winner blend is the dark harrar (CS-9.5) and the lighter Columbian (CS-8 or 7.5 maybe)
                  (2) As a SO, the darker harrar and sidamo are TERRIFIC (but I like that kind of coffee, so this is biased)
                  (3) The lighter harrar (and sidamo) are inoffensive, but the chocolate notes are not quite there.
                  (4) The lighter Columbian is nicer than the darker. Thanks Mal.

                  So an interesting time overall, with sidamo beating harrar; but the family preferrs the Columbian/Harrar blend over all.

                  Ive looked around, but been unable to find a rule-of-thumb roasting guide anywhere. Seems to me someone (Hi there Mal!!) could do the world a service and put some guidelines up that give ballpark guidelines. "Sth Americans - light, CS7-8, before 2nd crack; Ethiopians - darker, CS8-10; ...." Itd be REALLY handy to have something like that kicking around!

                  /Kevin

                  Comment


                  • #10
                    Re: Optimising Popper Roasting

                    Kevin, When I first got my popper (the warehouse cascade brand) Hazbeanand I did a test and found his B&D popper runs a little hotter than mine.

                    You may find that that may affect your roasts too.

                    Comment


                    • #11
                      Re: Optimising Popper Roasting

                      Yes indeed, Cindy. I think its actually the same popper as we tested --
                      I "loaned" one to Kevin soon after that. Apparently its now nearly
                      dead (all in the name of science). Luckily we picked up another one
                      for $5 recently at a garage sale so there is once again a spare for someone
                      to "borrow".

                      Comment


                      • #12
                        Re: Optimising Popper Roasting

                        Its not dead yet! Dying, yes, dead no! When it dies, Ill give it back so you can do the warranty claim ;D

                        Anyway - I dont know if it runs hotter than normal - but it struggles in the winter! Need a cardboard box to achieve second crack!

                        /Kevin

                        Comment


                        • #13
                          Re: Optimising Popper Roasting

                          I think that one has a higher wattage from memory.

                          It is tough getting to second crack. Possibly because most days do not get above 10C in these here hills. I place my popper in a box and occasionally put a lump of wood or something over the chimney to ramp up the heat a bit.

                          Comment


                          • #14
                            Re: Optimising Popper Roasting

                            Well, Ive resorted to a box to boost the temperature to 2C. Attached is a screenshot from qtdmm which I use to monitor the roast. Ive controlled the temperature using the highly sophisticated "finger on the power switch" pulse width modulation technique Cheap, and it kind of works.

                            Some notes for the anally paranoid - the temperature readings are taken using a cheap K-type thermocouple (+/- 3%) attached to a cheap DMM (+/- 3% again) - so the absolute values arent important. FC was at 203-204C and 2C was about 230-232C.

                            This was a Sidamo (from June Bean Bay) and it is fantastic but I like ethiopian coffees - so Im biased.

                            This, and all the roasts Ive done in the last couple of weeks, prove to me that a popper is pretty lethal in terms of achieving desired roast profiles. I have a cunning plan to build a more automated roaster on the basis of these experiments (cue: lightning, hunchback and haunting "pull the switch Igor!"....).

                            /Kevin

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