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Corretto Batch Size - Heat Input Adjustments?

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  • Corretto Batch Size - Heat Input Adjustments?

    Hi all
    About to start doing some regular roasting for some friends, so will be upping my batch size requirements. Currently I only do 350g for my personal usage, but I understand that doing double that is quite achievable in a corretto.

    My question is… are there any other snobbers who vary their batch sizes in the corretto regularly (rather than doing multiple back-to-back roasts), and if so, what are the ball park adjustments you have discovered are required?

    My guess is if I went to a 700g roast, I'd need to increase the temp early on to get more heat into the cold beans initially, then drop the temp more just before 1C so the roast doesn't run away. Does that sound right?

    Any advice much appreciated! (my first attempts will be this weekend one way or another - so I'll be sure to post my trial & error finding too!)

    Cheers Matt

  • #2
    I still do the odd 500 to 550g green for others. Definitely need more juice early on, 250 to 300deg starting temp on gun as opposed to 120 to 150 for my 300g batches.

    YES I find it more tricky to control on approach to FC. RFC can really get away from me if I'm not concentrating and being a bit more hands on with adjusting temps on gun.

    My pan is not insulated so I try to avoid any drastic changes with large temp changes on gun, I'd rather be slightly over in temp and let it settle, than end up chasing to avoid a stall.

    Having an insulated pan you should build up a pretty decent thermal mass.

    I'm honestly thinking of going back to bigger batches, when I nail them they seem to be just overall more wow than my smaller ones. I think if I insulated that could help with the smaller batches.

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    • #3
      Thanks Steve
      Sounds like the gut reaction might be right. And I am looking forward to tasting the difference - I'm sure the larger batches, if I can control them well should be pretty flavoursome - that large thermal mass/less airflow must change things a bit…
      Will let you know how I get on!
      Matt

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      • #4
        Hi Matt,
        I regularly change my roasting batch size depending on what and who I'm roasting for.
        I've pushed mine to 850g (green) a few times and very comfortable with 750g. I have a large rectangular bread bin tho.
        You are correct with your thoughts about more and less heat at the right times. You may also have to back the heat off between 1st and 2nd cracks.
        I found it was just experience with that amount of thermal mass to know when and how much to change the heat input.
        The things I found were:

        - insulating with fire blanket helped
        - cooler doesn't work as quick
        - beans expand in size and get closer to heat gun.
        My gun is at a fixed height, resting on the bread machine, and I change the heat input (bosch gun). The increase in bean volume is noticable for larger batch sizes and can get too close to the heat gun nozzle.

        I've considered a cover for the larger roast but haven't played with that yet.

        Good luck - I'm sure you wont spoil them.

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        • #5
          Thanks Roubaix
          That's great info! I'm working with a medium (standard kinda size) rectangular pan, so doubt I could go to 850, but 700 should be possible. With the pan & lid insulated, my required heat inputs have dropped dramatically, so hopefully even with bean expansion causing the beans to getting closer to the gun, the lower temps would still prevent scorching, but guess we'll see :-)
          I'll be also to see whether the DMM still reads correctly with all the extra beans on top - might need to have varying holes dependent on batch size…?

          Matt

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          • #6
            Hope its not off topic??

            On the physical limit side of things, I found that doing an 800g roast (only did that once) the beans started to escape over the top of the Roasting Pan as they expanded during the process.
            This encouraged me to raise the sides of the Pan and make a mental note that 600g should be the max for the Breville Oval Pan. (Internal mm H170 x W185 x D130). H includes the 30mm added by the extension.
            So that idea might be helpful ???

            I did quite a few 600g roasts with only a few escaping and then the added fact that 300g fits snuggly into the 250g bags is also a consideration.

            Cheers
            Sando

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            • #7
              Hi Sando
              Yeah - there's a thought… My lid fits pretty snuggly right over the pan currently - so the main issue would be beans blocking/jumping out of the exhaust or input ports.
              I don't plan to go to 800, but 700 would be good… I guess I'll give it a go and see whether we end up with any "Steve McQueens" during the first run LOL!

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              • #8
                Well, that was an experience! Kinda like driving a semi trailer compared to a 998 Ducati!

                Here's the profile, plus temp inputs - a real mad hatters tea party! DMM readings all over the joint.
                BUT…
                I'll see how it cups this morning before making further comment… more tk


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                • #9
                  Well I'll be!
                  I jumped into that batch (Mocha Java + blend) today with 12 hours rest (hey - people are going to be paying for this!) in some flat whites - and amazing! Beautiful chocolate…
                  I was expecting a disaster - but it blew me away. That much flavour so soon after roasting!
                  I'll keep tweaking these larger batch sizes!
                  Matt

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                  • #10
                    Well 525g batch today. The DMM read much more accurately (fairly comparable to my normal profile) but still slower despite upping the temps 2 steps up on my ambient adjustments.
                    But looking promising!

                    Matt

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                    • #11
                      Gotta say DBC, I've been following your posts closely and am keen to replicate your technique and set up. Keep up the good work and I'll definitely be shooting you a PM soon.

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                      • #12
                        Silly question and maybe off topic. Why and how do you insulate the pan?

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                        • #13
                          Haven't done it myself but from countless thread reading a fire blanket supposedly works if wrapped around the actual breadpan and it is for keeping the needed temps of the gun down so as to avoid tipping/scorching and giving a better all over heat. Someone correct me if I am wrong.

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                          • #14
                            Spot on Marcism ;-)
                            I found I achieved a gentler, deeper, sweeter roast than without insulation, and with less heat input. I just used a fire blanket - wrapped and held it there with wire. Well worth it!
                            Matt

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                            • #15
                              Hah it's all the roasting I do in my dreams. Time to get building I think!

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