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Roasting slow-fast profile in the KKTO

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  • #16
    Sorry I've turned this into a "how my roaster operates this week" thread, but hopefully it's a bit of relief for other KKTO owners. I'll report back on Friday or Saturday once I've had a chance to do more batches.

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    • #17
      I guess you could start up a new thread and ask Javaphile if he wouldn't mind moving the relevant posts into it...

      Mal.

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      • #18
        So I gave Steve82's tips a go. Seemed a lot better to me.

        In a whole bunch of ways my profile _looks_ the same as my previously uploaded profiles but with the much lower environment temperature, and a slightly slower drying phase, I've definitely got a bit more aroma and fruity acidity off the freshly roasted beans when I had a munch on one.

        No photos of my roasts. Unfortunately on my first Ethiopian roast my vacuum cleaner suction dropped too much to move the beans (filter problem) so a significant portion of them sat unmoving in the roasting chamber while I sorted it out... but hopefully the slightly burnt surface won't mask the flavour too much and I can make an assessment on how it improved on last weeks efforts. I also did a Rwandan and another Ethiopian with a larger batch size.

        Would love comments and thoughts on this profile of the first Ethiopian batch - 470g.


        One thing I wasn't sure with Steve's recommendation was whether I was ramping right from the turning point onward, or ramping from the end of drying phase. But looking at Matt's profiles and the power levels there, looks like from the get go is what I'm looking for.

        Matt, you suggest that the roast seemed long for the Ethiopian origin - this one is kind of the same. Dropped at 17 minutes, as my ROR was not carrying me any closer to my 218/220 target, due to evaporative cooling I suspect after first crack. However, my first crack still happened at 14 minutes, which was later than I was hoping.

        Still need to work out what is happening with my probe, and why first crack happens at 205 degrees.

        One thing I'm reluctant to do is drop my batch weight any less than 470g of green (that is, 400g of roasted with 15% loss). I roast for mates, and trying to roast ~1.5-2kg of coffee on a Friday arvo when I'm resorting to only putting 400g into the roaster to begin with sounds far too painful to me.

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        • #19
          Originally posted by readeral View Post
          Matt, you suggest that the roast seemed long for the Ethiopian origin - this one is kind of the same. Dropped at 17 minutes, as my ROR was not carrying me any closer to my 218/220 target, due to evaporative cooling I suspect after first crack. However, my first crack still happened at 14 minutes, which was later than I was hoping.
          Howdy
          It was more that one of those Ethiopian roasts seemed so much longer than all the other origins. I tend to find that Ethiopians tend to best best when roasted from faster to baseline, then the Brasil/Columbians like baseline–slower. Just comparing all those different profiles

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          • #20
            Originally posted by DesigningByCoffee View Post
            the Brasil/Columbians like baseline–slower.
            I usually interpret this as a gentler profile, mainly for lower grown beans...

            Mal.

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            • #21
              I'm partly wondering about processing method. A lot of the beans I've struggled with this year have been dry processed beans, rather than wet processed. The bean I've had the most success with was the Mexico El Malinal which is a wet process.

              Can anyone give me insight to my hunch?

              As a result I'm thinking of picking up some Costa Rica Tarrazu San Marcos as my ongoing staple (as there is no more of the Mexico on offer - knew I should've stocked up!). Andy doesn't specify the processing method, but a quick google suggests it is washed. What do you think?

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              • #22
                G'day Al...

                I don't have any blanket method for roasting either of those processing types as there is quite a lot of variability within each type. There is some info to be found however that may give you some very generalised guidelines to follow, such as this info here...
                Fundamentals - Coffee Roasting - Dry Process vs. Washed Coffees

                Mal.

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                • #23
                  Ok, so I’ve had a munch on some of the Rwandan beans, and there’s a delightful blueberry flavour! I’ve always known these beans could do it, and I’ve never ever got it which has been what’ driving my obsessive change attempts.
                  Unfortunately I’ve also detected ashiness and would love some advice on this. My bean mass temp only hit 215 degrees before dropping, and it didn’t get to second crack (nor are the beans oily) so it’s some other thing.
                  These beans have never burnt on a preheated system set to 265, so I’m inclined to think that charging at 200 degrees is unlikely to have caused my problem either, but that leaves me a little stumped. I may be wrong on both these thoughts however.


                  It’s hard to tell as this is a bit of a mottled bean anyway, but maybe there is some charring in the seam - but it doesn’t look like I have charring throughout the bean. I’m not quite sure what tweak to make to avoid it.


                  Here’s the profile I ended up with. It was a 470g green batch, when I’m used to putting 600g green in, so this would likely have played a part as well. With this roast, I couldn’t push it any deeper, even though I was trying to - so didn’t have enough energy into first crack to carry it. I’m playing a balancing game which is proving difficult!

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                  • #24
                    Originally posted by DesigningByCoffee View Post
                    Howdy
                    It was more that one of those Ethiopian roasts seemed so much longer than all the other origins. I tend to find that Ethiopians tend to best best when roasted from faster to baseline, then the Brasil/Columbians like baseline–slower. Just comparing all those different profiles
                    So if you wanted to roast faster to baseline, there are different variables you could play with: higher preheat, lower batch volume, less development after first crack, higher heat input across the roast.

                    My question is, if you were to put these in an order of priority, what would you say?

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                    • #25
                      Ok - my next experiments are to:
                      1. Drop my charge temperature to 190
                      2. Draw out the drying phase an extra minute, and delay ramping my power levels up until about 1m30s into the roast (rather than right from the get go).
                      3. Prop open the roaster slightly (haven't worked this out yet - maybe I'll just make more gaps in my rubber seal) to get more airflow out of the system, and hopefully carrying moisture with it.

                      I'm reading from one of Boot's Roast articles that high moisture content requires careful drying phase, and that poor air pressure (and I expect that a closed environment like the KKTO will have quite poor air pressure, even if it has high air speed) will give baked and flattened flavours, and a dulled acidity. Makes sense. It's an oven designed to bake... Can't say that I've always had a dulled acidity in my KKTO roasts as in the past I've dropped quite light, but I can definitely vouch for the baked flavours which I am constantly fighting against.

                      The risk of opening up the lip of the roaster is that as the convection air is forced sideways across the face of the glass top, I might just be forcing my hot air out of the roaster from the get go, and lessening what heat energy I have available to actually get my roasts over the first crack line and into proper full development. In the inverse, I'm letting moist air out of the system, avoiding evaporative cooling, and also avoiding a super-hot moist environment damaging the roasting beans.

                      I remember reading previously about people modifying the fan blade angles of a TO in order to get more airflow straight down (and actually seeing a subsequent decrease in roast times). This might be something for me to look into doing, but given there was no discussion of roast defects (presence or absence of) with reference to those mods, I'm hesitant.

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                      • #26
                        Also (sorry about the spam) but some of my beans (at least in the Rwandan roast) did bulge open - which I've always known is an indicator of too much heat. My question is - is this too much heat when dropped into the roaster, or is it too much heat in general from the environment, once the drying phase is over?

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                        • #27
                          I tend to keep turning point consistent by adjusting my preheat and 'drop zone' gun temp inputs dependent upon ambient and green bean temps. Then increase the ramp from TP to 1C, and leave the post 1C to 2C zone alone unless roasting for filter.

                          By your tasting notes, it could be than heat / fan is too hot early on in development. I'd try a slower start (possibly less preheat but certainly post TP heat input) but then increasing higher towards 1C. Beans should be more resilient to higher heat input then

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                          • #28
                            Cool thanks Matt - I just wrote a reply but not sure where it's gone...

                            What is 'drop zone'? Re: my turning point, I usually aim for a consistent TP of 80 degrees after 1 minute. My probe is one of Andy's 100mm probes, 3mm wide, so it's pretty quick responding. Alas, I think I've killed it as where FC used to be 200 degrees, it then shifted to 205 degrees, and now it's 206-208 degrees.

                            Looking back over Steve's comments, I can see that he was trying to get me to avoid hitting my max ET early in the roast. By ramping right from the start, I still hit my max ET four or so minutes out from first crack. I'm assuming that by delaying my ramp up, I can get better momentum into first crack for a more rigorous crack, as well as avoiding those high environment temperature negatives, damaged beans from earlier high heat input and hopefully carrying it into post-FC development a lot better.

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                            • #29
                              I call it the drop zone. I basically preheat the corretto, drop the beans in cold at a certain preheat temp (120-140°), and then the zone from load to the TP is the drop zone (sure it has an official name ). I keep the gun running gently at different temps in this zone to get a consistent TP, but at around 40°. Seems to work for me

                              Could the probe be moving? If you change batch size, you might need to adjust the probe. I have two locations for 350g and 750g batches - get it wrong and it reads 10° out.

                              I think your right about ET - lower at the start, hit it harder late. If it is too high early, you're more likely to scorch and tips beans (though I've never experienced this myself!) so might be talking out of my hat!

                              Matt

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                              • #30
                                I'm almost at the point of giving up on the KKTO. Almost. Invested hundreds of hours into building the roaster and trying to get a roast that I'm close to satisfied with (granted I'll never be thoroughly satisfied. That's the game of any sort of skill), but I rarely see one!

                                I did 4 roasts today to try to nail this slow fast process. I'll upload the graphs of the first 3.. They were "ok". First two roasts were 500 grams and the third was 400g. My last roast I tried 600g which is what I used to do back when I preheated high and left it high, and managed to have the most uneven roast I've had for a long time, with many burnt beans. Needless to say, new approach does not do kindly with larger batches.

                                My biggest concern on my first roast was that with an ET of 200 degrees, I wasn't approaching end of drying phase before 8 or so minutes, and so started my ramp before drying was over. I tried ramping over 5 minutes to 255, and eventually pushed it to 265 to try to get a better run up to 1C. It fell short, and in doing so, I then didn't have enough energy to push it through to first crack (206 degrees) let alone much beyond it.

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                                In my second roast, I tried an ET preheat of 210, and ramping earlier, letting the machine just ramp as quickly as possible. This was slightly better, and first crack appeared to come earlier (203), but again I had to give it a further boost before 1C and I couldn't get it much past a light roast after backing off from my elevated ET.
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                                My third roast I dropped down to 400g (probably the minimum volume I can get away with in this system) to try and give myself access to more energy. I also decided that instead of worrying about what the ET was, I would try to maintain some sort of steady RoR. This was probably the most successful of them all in terms of how dark I could take it - finally an espresso-worthy roast if judging by temperature alone - but 1C came really late (214), and I didn't develop much beyond this temperature.
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                                Every roast had some ashy beans.

                                I'll cup all the roasts tomorrow, but I doubt any of them will have that fruity acidity I had last week. What a depressing day of roasting.

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