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Thread: Optimum Batch Size for a Corretto???

  1. #1
    Mal Dimal's Avatar
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    Optimum Batch Size for a Corretto???

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Quote Originally Posted by ozscott link=1193913160/20#37 date=1217840838
    I have found with 1kg with these 2 batches is much easier to control the roast after the FC to stretch out to the SC.
    Yep, me too.....

    For that matter, the entire roast process is a whole lot smoother with larger batches; probably a factor of heatgun output versus BM bread-pan size I suppose. Ive found with my rig that if I partially cover the pan (in my case I use a piece of 100mm x 12mm pine) you dont need to have the heatgun nozzle so close to the bean mass surface as more of the applied heat is retained. Had to re-learn the characteristics of my process again for a few batches but all is good now.... ;)

    Mal.

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    Re: Peru Grace Estate

    Thats interesting guys... weve been sticking to 400g roasts in our Corretto after a couple of 600g roasts went too quickly to SC. I reasoned that the larger thermal mass of the beans was keeping more of the heat produced by FC in, and causing a bit of a runaway roast... This is probably true, but from what you guys said, it might be worth our persevering - and learning to lower the heat just a touch before FC - to keep it in control...

    Cheers
    Stuart.

  3. #3
    Sleep is overrated Thundergod's Avatar
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    Re: Peru Grace Estate

    I dont like going back to 300g roasts after having gotten used to 600g ones.

    I find the bigger ones easier.

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    Senior Member ozscott's Avatar
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    Re: Peru Grace Estate

    Stuart and TG - its interesting but I find that 1kg lots are now easier to control than say 500-600. I am surprised at how easy the 1kg is - pleasantly so.

    Cheers

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    CoffeeSnobs Owner Andy's Avatar
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    Re: Peru Grace Estate


    All roasting devices have a "sweet spot" where the load vs heat application is just right and the planets align to give a perfect roast.

    The manufacturers seem to have no idea and quote a batch size to put something on the carton I think and its worse with a home made roaster as you dont even have a starting point.

    I suggest everyone has a play with the volumes of your roasts to find your own roasting sweet spot.... and then adjust to suit the bean density differences. As I always say, you need to do this yourself, dont just use what works for others as the amount of variables are huge.

    Even when you think you have found the right volume adjust 10% up and down from that mark to confirm.

    :)

  6. #6
    Senior Member greenman's Avatar
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    Re: Peru Grace Estate

    I usually roast 600g batches, yesterday I had 300g of Kenya A left so I did a roast, with the smaller quantity the beans flew all over the place and I lost a few out of the bucket, definitely a lot more stable with a larger batch.
    I have gone to 800g with good results.........................

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    Mal Dimal's Avatar
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    Re: Peru Grace Estate

    From Andys post above....

    Youve got to be just as careful to ensure that you dont overload your BM too, not so much from a spillage perspective (and thats not a good thing of course) but from a roast capacity perspective. You have to make sure that you can still exert control over the roast profile with the heatgun that you use, e.g. steepening up the Rolling FC ramp... Unless your heatgun has the thermal output to allow this (without the nozzle sitting on top of the bean mass) then you need to reduce the batch size until such time as you are able to manage the profile; or, get a bigger heatgun or use a gas torch of some description ;).

    Mal.

  8. #8
    Senior Member ozscott's Avatar
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    Re: Peru Grace Estate

    Thanks Andy and Mal - I wonder if I should back it down a little. The 1kg works with a good climb with the gun off the the beans a couple of inches to about 140 degrees (say 14c/min climb or higher depending on profile required) but then it goes south with fluctuating climb of no more than 5-6 degrees leading to the first crack - and thats with the HG one inch off the top of the bean mass (I dont close the lid anymore because I think that killed my Ryobi). Having said that it doesnt stall and it rounds off the profile nicely into the FC and then the climb rate rockets back up. The profile looks good for the ones that I have done. I am keen to see how they taste after a few days rest. I had one today and wasnt that impressed but it may need a little longer.

    Apart from what I observe above, is there anything else to look out for in trying to ascertain the sweet spot?

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    Mal Dimal's Avatar
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    Re: Peru Grace Estate

    Gday Oz,

    From the sounds of things, Id say you were right on the limit of your current setup mate. Its more to do with the thermal energy available and how this can be efficiently transferred to the bean mass without risking scorching the beans. Im probably pretty lucky with the Big Loaf BM we have as with the BM lid removed, the top of the bread pan sits proud of the BM casing by about 30mm. This allows me to fit a sliding lid directly over the bread pan and manage the roast in this way. I have roasted Kilo batches using this method with the heatgun nozzle about 75-80mm above the bean mass and still being in total control of the profile.

    I guess theres just a lot of thermal energy loss with the Corretto and this doesnt make for a very efficient roasting system but if you can develop some means of trapping the hot air currents within the bread pan for a little longer, then you will improve the efficiency by some amount and reduce the need to increase the thermal energy input for controllable 1.0 Kg roast batches. What works on my setup may, with suitable alterations, work on yours too Oz. My bread pan "lid" is nothing more than a piece of pine about 100mm(W) x 12mm(D) that has been routed out appropriately so that it is a snug fit over the lip of the bread pan. Quite simple but effective. I dont think it improves the efficiency all that much but it is enough to allow me the opportunity of steepening up the ramp to FC when I need to with a few bean varietals that seem to benefit from this, and that is all that I was after. Might be worth playing around with something similar that you can adjust "on the run" as needed.... :)

    Cheers mate,
    Mal.

  10. #10
    Senior Member ozscott's Avatar
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    Re: Peru Grace Estate

    Mal - thanks mate:) I will get the router out for a run and see what I can come up with. My Big Loaf has the bread bowl recessed into the machine, but I could make a lid and stick a hole in it for the steel part only of the heat gun to fit in with say 5mm around and leaving the plastic shroud of the gun out of harms way...I like it and with the gap right there should be no scorching of the pine (perhaps a pine flavoured bean:).

    Cheers and thanks again mate for you kind assistance.

  11. #11
    Senior Member ozscott's Avatar
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    Re: Optimum Batch Size for a Corretto???

    I suppose a gap on same side as the HG but separate from it would allow chaff to exit, heat to go around the beans before coming back to the exit side - assuming the HG is angle to the other side where the lid covers the mass completely, and it stops hot air being flogged out past the HGs plastic shroud.

    Cheers

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    Senior Member redzone121's Avatar
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    Re: Optimum Batch Size for a Corretto???

    Mal do you use just the one HG for 1kg roasts?

    I have a Big Loaf on stand by just waiting to have it wired so knead cycle is longer. I was planning on 2 HGs, I also have a new Ryobi HG for a bit more power, poor old predator is tapped out at 500watts. I was going to use them together?

    Back to topic, I am using a Predator HG $19NZ at the moment in a regular BM and its sweet spot seems to be 500-550gm roasts.

    CB

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    Re: Optimum Batch Size for a Corretto???

    Hi all,

    The smallest batch size weve done is 300g, and that actually works fine. Plenty of control and no flying beans. I wouldnt want to go any smaller though.

    400g has been our most common batch size, and I thought it was that "sweet spot" that has been mentioned - mainly because it required minimal adjustment of HG to get a FC @ 10-12min, SC @ 15-18min profile.

    We HAD tried a few 600g batches, but found that they ran away from us and we only got ~4 mins between FC and SC. After reading what Mal and others said, weve tried two 600g batches, and found that theyre fine, as long as youre conscientious with raising the HG at FC... For a 600g batch (compared to 400g), we need the HG much lower until FC, then raised much more after it.

    Last night we did a "dry run" (ie. without HG) to see how well different batch sizes stirred:
    400g - easy
    600g - equally easy
    700g - straining (big difference - motor changed pitch a little)
    800g - straining, occasionally stopping
    1.0kg - stalled

    So I think 600g seems to be a comfortable maximum. Havent noticed any differences in the cup (though we havent been looking for it), but larger batches do seem more "satisfying" for us as roasters (may be more even; slower temp changes etc.).

    Cheers
    Stuart.

  14. #14
    Senior Member Stan's Avatar
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    Re: Optimum Batch Size for a Corretto???

    I normally do 520gms as that fits into the bag when I am finished. I havent experimented with different amounts as the roast comes out even and it is convenient as it suits the bags I store them in. Further it is one less variable I have to deal with, if I maintain the amount I can then play with the height of the HG to vary the length of the roast. Also I am to cheap to buy new bags. ;)


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    Mal Dimal's Avatar
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    Re: Optimum Batch Size for a Corretto???

    Behmor Coffee Roaster
    Quote Originally Posted by redzone link=1217861457/0#11 date=1218064234
    Mal do you use just the one HG for 1kg roasts?

    I have a Big Loaf on stand by just waiting to have it wired so knead cycle is longer. I was planning on 2 HGs, I also have a new Ryobi HG for a bit more power, poor old predator is tapped out at 500watts. I was going to use them together?
    Yes mate, just the one.... A Ryobi 2000W 60/600C unit.

    I think it would do OK without the lid on the bread pan but as with Ozs experience, I think that a 1.0Kg batch done this way would be right on the edge of controllability. The lid just makes it a lot easier to control, no fuss or bother and as Oz has queried above, having the opening facing back towards the heatgun or on one side seems to work quite well. Allows for all the chaff to vent off and the air temperature of this exhausting air isnt high enough to cause any damage to the heatgun itself (so far ;)).

    Mal.



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