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  • Critique my roast profile (+technique)

    Hello wonderful snobs!

    I have been roasting on and off for ~12 months and have done about 20 batches. My setup is a coretto system: open breadmaker, heatgun on a tripod, heatsnot + artisan. I am looking for any pointers that may help me dial in my process. TBH, I'm not even sure what I'm supposed to be targeting profile wise, and have just made a huge amount of assumptions diving in.

    Currently I guess my charge temp based on previous roasts and interpolating between batch sizes. I have figured out for my system:

    Qty (grams) Charge Temp Temp drop Turning point
    200g 150*C 55*C 95*C
    300g 165*C 70*C 95*C
    400g 180*C 85*C 95*C
    500g 195*C 100*C 95*C

    So my 1st assumption is that I should target around 95*C turning point.

    The second thing I have been doing is trying to dial in when I pull my beans off.

    I have started off roasting the beanbay PNG Wahgi and Mexico El Truinfo:
    • I have found with the PNG I don't want it to go above 212*C, and about 30 sec into 1st crack.
    • With the Mexico the last batch I did (graph below) I went 50 sec into 1st crack to ride up to 212*C, although it's a little long into 1st crack for my liking.

    Should I be pulling beans off according to temp, or is timing into 1st crack best?


    Click image for larger version  Name:	2021-06-24 - 500g Mexico El Trufino.jpg Views:	0 Size:	66.6 ** ID:	871732


    I would say the Mexico batch in the graph above has been my best batch yet, but maybe a little too chocolatey for my liking but, I like a bit more acidity. Not sure if this is more a function of the bean, or the roast.

    Any feedback to help me on my way would be awesome!!!

    Cheers legends.

  • #2
    It looks like you are trying to roast as though you have a drum roaster, not a corretto. I wouldn't bother pre-heating or aiming for a turning point as you don't have a big chunk of metal that needs to get hot. Do you use insulation and/or a cover on the breadpan?

    Just load your beans into the bread pan, turn on the agitator, heat gun and roast tracker and away you go. Depending on the batch size you should achieve first crack at ~200°c in around 15 mins. Then stop the roast when the desired roast depth is reached. When that is is your choice but your 215° is not a bad number if you are looking for brightness. Rather generally, short, light roasts increase acidity while longer, darker roasts are smooth and possibly more chocolatey. Are you roasting for espresso or filter brews?

    However, the beauty of home roasting is that you can do your own thing so what others advise may not work for you. It might be worth trying some of the CS roasted as a benchmark.

    Comment


    • #3
      I would echo Flynn's comments and add my own.
      The roast time between FC & dropping is probably too short - 30 seconds to 1 minute seems really quick to me. I target more like 3-5 minutes albeit with larger batch sizes.
      Profile for beans will be both temperature and time - so you might find 212 degrees 'good' but extending the FC to drop time might develop more flavour.

      I have found that the larger batches easier to manage in the 400g+ mark. The roasts are less sensitive to changes in heat input.

      Comment


      • flynnaus
        flynnaus commented
        Editing a comment
        I have found that the larger batches easier to manage in the 400g+ mark. The roasts are less sensitive to changes in heat input.
        Yes, that's right. Too small and it's harder to maintain a steady temperature rise. Too big and the roast times blow out potentially resulting in loss of flavour

    • #4
      Originally posted by flynnaus View Post
      It looks like you are trying to roast as though you have a drum roaster, not a corretto. I wouldn't bother pre-heating or aiming for a turning point as you don't have a big chunk of metal that needs to get hot. Do you use insulation and/or a cover on the breadpan?

      Just load your beans into the bread pan, turn on the agitator, heat gun and roast tracker and away you go. Depending on the batch size you should achieve first crack at ~200°c in around 15 mins. Then stop the roast when the desired roast depth is reached. When that is is your choice but your 215° is not a bad number if you are looking for brightness. Rather generally, short, light roasts increase acidity while longer, darker roasts are smooth and possibly more chocolatey. Are you roasting for espresso or filter brews?
      I agree with flynnaus, no need for charge temps etc, just start from scratch and develop your profiles as you go and keeping records for reference.

      Comment


      • #5
        I did not know you didn't need to preheat! I do not use insultation, no.

        Thanks, those numbers give me a guide on aims for development time.

        I brew for RokPresso, so espresso.

        Thanks for your thoughts flynnaus!!

        Comment


        • #6
          Originally posted by WhatEverBeansNecessary View Post
          I would echo Flynn's comments and add my own.
          The roast time between FC & dropping is probably too short - 30 seconds to 1 minute seems really quick to me. I target more like 3-5 minutes albeit with larger batch sizes.
          Profile for beans will be both temperature and time - so you might find 212 degrees 'good' but extending the FC to drop time might develop more flavour.

          I have found that the larger batches easier to manage in the 400g+ mark. The roasts are less sensitive to changes in heat input.
          Do people generally reduce heat at 1st crack? Or keep heat / airflow / distance consistent throughout like I generally do?

          Comment


          • WhatEverBeansNecessary
            WhatEverBeansNecessary commented
            Editing a comment
            Generally (and it depends on your batch size, heat gun, ventilation etc) I keep it about the same or just bump it up slightly.
            Keep in mind once you hit FC the beans go from endothermic to exothermic (slightly) so they produce heat rather than consume it (this is super simplified 'chemistry' of it all) - but you also need to continue to increase the temperature. So will be a balancing act between beans heating themselves and adding in extra heat.

          • Lyrebird
            Lyrebird commented
            Editing a comment
            Horses for courses. I keep air flow at maximum and reduce inlet air temperature in several steps over the course of the roast. One or two of these steps are usually after the probe temperature has passed 200 oC so that would put them after first crack (I don't bother tracking FC as I don't think it matters).

          • Nedplimpton
            Nedplimpton commented
            Editing a comment
            I think unfortunately my heatgun doesn't push enough air between setting 2 and 3. At 3 it's too hot, and at 2 my curve flattens right off. Might need to raise the heatgun instead.

        • #7
          Might be worth simply upgrading the heat gun. I went to the Bosch 2000W gun with the digital readout after blowing up the equivalent Makita. Available for about $150 from tool shops including big green shed, that's the equivalent of about 6 kg of coffee.

          Also, insulate the pan on the breadmaker, reducing heat loss improves consistency for basically no money if you have access to rockwool or similar. If you don't I'll give you some for the cost of shipping.

          Comment


          • Nedplimpton
            Nedplimpton commented
            Editing a comment
            What type of insulation do you use?

          • Lyrebird
            Lyrebird commented
            Editing a comment
            Ordinary rockwool for the sides, I align the joint so the thermocouple fitting doesn't push the rockwool down. I cut a lid to fit the breadmaker from silicone foam (sold as ironing pads).

            I tried ceramic oven insulation but it is too fragile.

            The insulation value will be set by the pan spacing. Mine has about 25mm clearance between the pan and the sides of the breadmaker so that gives you about R 0.5 (common insulation is all clustered around R 20 per metre thickness)

        • #8
          Thought I’d piggyback off this with some further questions.

          Any feedback on the airflow setting in the heatgun?

          Assuming most heatguns have two (low and high) settings, do you keep it on high airflow throughout the whole roast?

          Also how do you handle exhaust?
          Do you leave ~25% of the lid off permanently or do you progressively widen the lid gap as the roast goes?

          Comment


          • WhatEverBeansNecessary
            WhatEverBeansNecessary commented
            Editing a comment
            I have the ozito heat gun (cheapest with variable temp) and find I only use the lower fan setting. The higher speed I can't hear first crack well enough and have heard but not verified the higher speed dries the beans out too much.

          • Nedplimpton
            Nedplimpton commented
            Editing a comment
            I purchased a rockwell heat gun as it had more control than the Makita that was available nearby (tried to find bosch too, no avail).

            It has 3 temperature settings: 25°C / 350°C / 550°C

            I keep it on high flow (550*C) the whole roast. The 350*C flattens out the curve completely I find.

            Not lid, no exhaust, I just keep the lid open and direct the gun down into the pan. Looks like I might need to tinker.


            What should I try 1st? Insulate / build a lid / new heatgun?

          • Dimal
            Dimal commented
            Editing a comment
            I'd go for a Lid and Insulation first, little cost and significant benefit.
            You can then grab a new Bosch HG or similar at some future date from one of the big Tool Retailers that do online sales...

        • #9
          Originally posted by zuroy View Post
          Also how do you handle exhaust? Do you leave ~25% of the lid off permanently or do you progressively widen the lid gap as the roast goes?
          I have the Bosch 2000w variable temp heatgun that Lyrebird mentioned. It has three fan speeds. I worked out my own roast profile based on the profile Mal developed.
          I use a ceramic tile for a lid which covers almost half of the bread pan. I direct the HG to one side of the opening and use a fan to blow the chaff and exhaust away and don't need to adjust the gap during the roast.

          Comment


          • #10
            Originally posted by zuroy View Post
            Thought I’d piggyback off this with some further questions.

            Any feedback on the airflow setting in the heatgun?

            Assuming most heatguns have two (low and high) settings, do you keep it on high airflow throughout the whole roast?
            Mine has three but I leave it on the highest setting at all times. I find lower flows give more "bakedness" as I found to my cost when the Makita was clogged up.

            My theory is that baked flavour is actually caused by the coffee stewing.

            Originally posted by zuroy View Post
            Also how do you handle exhaust?
            Do you leave ~25% of the lid off permanently or do you progressively widen the lid gap as the roast goes?
            I have a 40mm hole in the silicone foam pad that fits a stainless steel elbow that exhausts into a wine box with a cloth lid (a BeanBay bag) as chaff catcher. Easy for me I have spare stainless fittings etc lying around.

            I tried connecting it to a full scale workshop dust and chip extractor but this seemed to pull too much hot air away from the coffee so it was counterproductive.

            Comment


            • #11
              Thanks I have a steel elbow but it might be a bit too long (20cm each length and 40mm diameter) so I wasn’t sure if that was affecting my roast flavours. I did a roast yesterday without the steel and just let chaff fly everyone so I’ll compare.

              Nedplimpton - I used a fire blanket as insulation and that’s at Bunnings for under $10 (and you’ll have plenty to spare).

              Comment

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