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Roasting slow-fast profile in the KKTO

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  • Roasting slow-fast profile in the KKTO

    I'm really struggling to retain any aromatics in my KKTO roasts, and maybe 1 in 10 roasts has the fruity acidity I'm so keen to find. It might be to do with too high a heat level and possibly an airflow thing, but I'm not experienced enough to troubleshoot. I'm sure it's just my skills lacking, but I'm almost inclined to stop searching and just resign myself to darker cocoa-like roasts. It's a bummer, given the tantalising descriptions Andy puts on these coffees. I know it's in there, just a bit too amateur to make it happen!

  • #2
    Do you have any roast profile samples that you could post up Al?
    Might help us to try and help you...

    Mal.

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    • #3
      Sure, I'll prepare a few of my recent ones. TBH, it's my first winter of roasting in the KKTO (last winter it was a popper), so that's also thrown me a little.

      Comment


      • #4
        Ok - here's a bit of a recent cross-section.
        First is a Mexican, 600g batch, which has been my most consistently successful bean to roast this year. Been awesome. Sadly, I just ran out. Alas. I enjoy roasting this bean, and the results. It seems to like the high temperatures pretty well.
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        Second is a Peru 600g batch
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        The next 3 I roasted this week, and have lowered my charge weight from 600g to 500g to try have a little more energy in the system, and to control it better. So, as you'll note, I've dropped my environment temperature from 265 down to 250/255 range.

        Peru 2 - this one I was trying to push through to a 2nd crack, but it actually ended up not getting anywhere close, and I had to drop it as a light/medium roast.
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        Ethiopia:
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        Rwanda:
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        I'm conscious that the transfer of heat into the bean is not just a matter of environment temperature, but a combination of airflow and available heat (as well as bean density etc. obviously playing a part) but right now I don't have control over my air speed, only my element, which I still haven't wrapped my head around PWM to keep it at a constant power level (it still pulses on and off once it reaches my PID preset of 265/250-255). That's a project for once my sparky friend has a little more time to help me.

        I also have been preheating to a stable 265 degrees, which might be a bit too much, but I haven't been getting any tipping or scorching, so have kept it there. I've been finding that 250 can do the job, but really only if I drop my charge weight. Part of me suspects that it's with the high drop in temperature that I might be losing my volatiles and aroma.

        The final thing is that my bean thermocouple seems to have shifted in the past 6 months. I used to hit 1st crack predictably on 200 degrees, but now it comes around 205. Hard to know if it's the thermocouple, or if it's a delayed (by temperature) 1st crack due to too high temperatures, that is, by the time I start to hear the cracking (which may have started at 200) the system has already reached 205. *shrug* excuse the overthinking after a day full of assignment writing.

        Lastly - I have a flat burr grinder. Won't make much difference, but will have a slight impact in how the flavours make it into my cup. I use a Hario hand grinder for my cupping, but haven't been inspired to do that in the past few months.

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        • #5
          readeral, just my thoughts coming from 2000+ sample size drum roasts using the style of roast you seem to be chasing.

          You mention airflow control, this is critical to balancing the environment temp with the bean temp rate of rise. Also I do not think your elements going ON / OFF is ideal for this style.

          The first profiles I was thinking crikey you are spending a LONG time at 265 environment temp while going through the 150 to first crack zone. Straight away I was thinking ashy caramels / baked.

          The start of the roasts, up to 150 look really good. However they are out of proportion to the rest of your roast = the really long time you are taking between 150 and first crack.

          The start of your roast is quite aggressive and you are probably getting plenty of early roast development. With such a start I would be expecting to hit first crack start around 9 mins - with a steadily declining curve, slowly dropping environment temp = gently teasing heat from the system while keeping this balanced with ever increasing airflow = more convection as the roast nears the end. This requires one to have built up some thermal momentum earlier on to coast on.

          Off the top of my head from what I have seen / read and used a turbo oven for general cooking. I would say abandon your fast start and try for something along the lines of a slow start / fast finish profile - google it.

          Generally, take your time gently teasing out the moisture the from seeds until they are yellow, environment starting 200C very slowly rising. The curve will flatten slightly - like what others are calling the seattle dip.

          Ramping the heating up progressively to hit your max environment temp - say 250 - 255 around 8min mark. Hold steady until first crack is really going then gently wind back to find your optimum finish. If it is for manual brewing try dropping at the end of first crack, then another roast +30sec, +45, +1 min and so on. Otherwise find what gives you 3.5 to 4 mins to start of second for espresso and work backwards.

          If your roast times are overly long (FOR ME anything over 14 - 15 min is more of a bake) and you want to shorten them up, just keep reducing batch size while keeping your environment temp targets the same.

          Eventually you can wind back to where you can pull off a pretty much " straight line " profile to first crack start, then tapering off with a declining ROR for the finish, which in my experience is where it matters the most. I have done tones of experimenting comparing slow start / fast finish with a declining rate of rise finish and an RAO approved fast start / slow finish with declining rate of rise from start to finish. Great coffee is possible either way. FOR ME an increasing ROR after first crack is where things get roasty and worst case ashy.

          Just to illustrate the differences between the 3 basic style I mentioned, Slow start / fast finish with declining finish, generic straight line profile also with a declining finish and fast start / slow finish RAO rules . These roast are from 3 different origins.

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          Last edited by Steve82; 10 August 2016, 12:18 AM. Reason: Added profile pics

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          • #6
            Very helpful! I'll give it all a go. TBH it's a case of getting the best I can from items that honestly aren't made to roast coffee... But that's where most of us are at. I will be modifying that element when I can, and putting a controller on my fan too eventually. All a matter of time.
            The time from 150 to FC has always been the thing that got to me. Never short enough for my liking. It's why I pursued the high preheat in the first place in an effort to reduce the overall time to FC. I'll try ramping my ET from 200 to 250 as you suggest and report back.

            Interestingly, unless I'm careless, I rarely get ashy flavours. Baked however, is probably a feature.

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            • #7
              Originally posted by readeral View Post
              Very helpful! I'll give it all a go. TBH it's a case of getting the best I can from items that honestly aren't made to roast coffee... But that's where most of us are at. I will be modifying that element when I can, and putting a controller on my fan too eventually. All a matter of time.
              The time from 150 to FC has always been the thing that got to me. Never short enough for my liking. It's why I pursued the high preheat in the first place in an effort to reduce the overall time to FC. I'll try ramping my ET from 200 to 250 as you suggest and report back.

              Interestingly, unless I'm careless, I rarely get ashy flavours. Baked however, is probably a feature.
              Lots of great advice from Steve

              I would second the ramping advice. Fast start, long slow reducing curve, esp after 1C gives pretty flat flavours in a corretto too.

              As to winter roasting, that does make it hard, depending on how 'wintery' your winters are! The TO is sucking in very cold air, so is bound to be slowing everything down. Case in point was your ethiopian - that seemed very long for that origin?
              I'm not sure how to solve that in a TO. Steve mentioned smaller batches. Or maybe you could use a small blow heater over the top of it so the air it is drawing is warmer? Just thinking leftfield… Some KKTO builders have added a good adjustable heatgun to the system too - that could help with ramping more quickly when required, larger batches or to deal with cold weather. But then again - if you're going to do that, you might as well roast in a corretto!

              Let us know how you get on…
              Matt

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              • #8
                Oh, I'm in Sydney Matt. No winteriness compared to your neck of the mountains. I'm just being a wuss.

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                • #9
                  Also, after pulling the TO apart, there is almost no air transfer from outside the system in. All those vents on the side of the unit are merely for keeping the electronics up top cool. At least that's the case with my Aldi TO. It surprised us when we busted it open for mods, and I've been tempted ever since to put some sort of adjustable vent in the side of my roasting chamber.

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                  • #10
                    And that causes problems for evaporation as it gets pretty humid inside the system without intervention. There's a gap I've put in for my rubber seal which lets enough out during summer, but in winter I've been finding its too much moisture in the hot air. Releasing it needs to be done carefully otherwise the roast runs away. A slower drying phase will definitely help with managing this.

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                    • #11
                      Just read through this recent discussion. I have no experience with the KKTO so can't help with specifics, but the thing that sprung to mind when I read your initial post Al was that you need to stretch the drying phase. So I can only echo the sentiments above. I know you like to read and research - have you read the articles on Coffee Shrub about stretching the roast? Could be some good info in there for you.
                      So it would depend on the bean, but in your position I'd be wanting to stretch the drying phase then ramp up for a definitive 1C, taking care not to let it get away on you if it's the sort of coffee that has that potential. The other considerations would be air flow and adequate exhaust/venting. Increasing airflow just around 1C would be good if that's possible on your set up.

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                      • #12
                        Originally posted by readeral View Post
                        And that causes problems for evaporation as it gets pretty humid inside the system without intervention. There's a gap I've put in for my rubber seal which lets enough out during summer, but in winter I've been finding its too much moisture in the hot air. Releasing it needs to be done carefully otherwise the roast runs away. A slower drying phase will definitely help with managing this.
                        This is a pertinent observation. Have a read up on evaporative cooling in regards to " drying stage ". From what you are describing it would be a fair assumption there is lots of it going on. Definitely need to work out some kind of appropriate level of flow IN / OUT through the system.

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                        • #13
                          Nothing left for me to say really...
                          Steve and Matt have nailed what I would also suggest.
                          Let us know how you go Al...

                          The intrinsic characteristic of the KKTO to cause an extremely humid roasting environment is one I could never quite overcome and is one of the reasons why I reverted back to a Corretto at the time.

                          Even up where we are, some roasts literally caused pools of condensation to collect in the bottom of the roaster because there was just nowhere for it to go; even with a small gap in the top seal... I know this doesn't cause concern for all KKTO operators but it was a limiting factor for me to properly control each roast.

                          Mal.

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                          • #14
                            Originally posted by LeroyC View Post
                            Just read through this recent discussion. I have no experience with the KKTO so can't help with specifics, but the thing that sprung to mind when I read your initial post Al was that you need to stretch the drying phase. So I can only echo the sentiments above. I know you like to read and research - have you read the articles on Coffee Shrub about stretching the roast? Could be some good info in there for you.
                            So it would depend on the bean, but in your position I'd be wanting to stretch the drying phase then ramp up for a definitive 1C, taking care not to let it get away on you if it's the sort of coffee that has that potential. The other considerations would be air flow and adequate exhaust/venting. Increasing airflow just around 1C would be good if that's possible on your set up.
                            The biggest difficulty I've had Leroy is that everything is relative, and so working out what has been subjectively described elsewhere and trying to devise a principle in which to apply to my own system has been very difficult. The advice here however has been very specific and tailored to my questions and concerns which helps me breathe a sigh of relief! Short of working with a consultant, I'd reached the limits of what I could do myself, so all this advice is very welcome.

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                            • #15
                              Originally posted by Steve82 View Post
                              This is a pertinent observation. Have a read up on evaporative cooling in regards to " drying stage ". From what you are describing it would be a fair assumption there is lots of it going on. Definitely need to work out some kind of appropriate level of flow IN / OUT through the system.
                              It's _almost_ driving me to use a heat gun instead, just so I can have an opening for exhaust. We'll see what else I can just from this design first.

                              The evaporative cooling has been something I've been aware of for a while (ever since I started webering meat) but hadn't resolved yet. I'd been trying to avoid doing much more hole making (cutting this stainless steel really sucked!) but I think that's my only next course of action.

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