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Thread: Harrar Roast Profile

  1. #1
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    Harrar Roast Profile

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I've gone through about 1.5kgs of Harrar in my PID controlled popper, without much success (ie, not what I expected).

    I was getting splits in the beans, tipping, a wrinkly surface and a slightly charred taste.

    After digging though the threads here, it seems my steep profile early in the roast may be to blame. So I tried a "ramp roast" last night - much better colour, no wrinkling and minimal splitting/tipping. Smells better too.

    Pretty excited to see how it tastes in a few days.

    I'll post a profile later

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    Hi MrJack,

    Thanks for letting us know. What was the previous steep profile and what profile did you try that worked better? As in what times and temperatures?

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    Did 2 batches of Harrar Longberry in my wing-it drum roaster yesterday. Gentle heat for first 3min, then slow but steady up to first crack @ 14-15min - surprisingly muted first crack, and very little exothermic activity (tendency to stall if one usually backs off the heat a bit during first crack, as I do) - hit a quiet second crack 5min later and dumped ASAP.

    Not the easiest bean to roast in my limited experience, I'd love to hear how more experienced folks have dealt with it.

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    Re: Harrar Roast Profile

    As exothermic means PRODUCING heat (just like fire) I doubt it would cause the stalling. In effect, the beans heat themselves. According to my reading, the exothermic phase is short, at the onset of first crack and is followed by an endothermic phase (heat absorbing -where stalling can happen - if your heat input is infufficient to drive the chemical reaction).

    There are three things that can happen to the heat you apply - it raises the temperature of the beans, it melts or vapourises something in the bean and/or it drives an endothermic reaction and is absorbed without raising the temperature (Literally the heat energy becomes part of the chemicals produced in the beans).


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    Senior Member chokkidog's Avatar
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    Looks like it's back to school for me! :-(

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    Hi Chokkidog, thanks for the info. My roaster is a rotating billy-can over a 2 ring gas burner - I posted some pic's a few months ago. I'm using an IR thermometer at present.

    I usually back off the heat as soon as first crack starts until the temp starts to dip a little (2-3min later), so that the roast doesn't rush into second crack too quickly, the temp remains stable for several minutes. My understanding of an exothermic process is that it produces heat - therefore if I keep heating the roast at the same rate during first crack it will accelerate the rate of heating, making it difficult to control. From my reading it seems a good idea to extend the interval between first crack and second crack.

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    Senior Member Vinitasse's Avatar
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    Quote Originally Posted by MrJack View Post
    As exothermic means PRODUCING heat (just like fire) I doubt it would cause the stalling. In effect, the beans heat themselves. According to my reading, the exothermic phase is short, at the onset of first crack and is followed by an endothermic phase (heat absorbing -where stalling can happen - if your heat input is infufficient to drive the chemical reaction).

    There are three things that can happen to the heat you apply - it raises the temperature of the beans, it melts or vapourises something in the bean and/or it drives an endothermic reaction and is absorbed without raising the temperature (Literally the heat energy becomes part of the chemicals produced in the beans).

    Actually... Exothermic refers to the RELEASING of heat.... not the production of heat. And since heat is energy and energy must come from somewhere... i.e. from the bean itself... it just makes sense that as the bean loses energy by releasing its heat that it requires more energy input in order to keep the process going. And... by the way... there does happen to be a second exothermic phase following the one you pointed out... it's called Second Crack

    And... just my own humble opinion perhaps but methinks you would be playing silly buggers to challenge Chokkidog on his roasting knowledge

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    Senior Member chokkidog's Avatar
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    Hi haba,
    Looks like I misread/misunderstood a statement in an article some time a go and have been wrong ever since.8-(
    Like my teachers used to say, revision is always good, doh! The post sort of works if you swap the terms around but I deleted it
    so my poor form doesn't confuse others.
    I've found that 3.5 to 5 minutes between 1st and 2nd crack gives me the best results. (mostly 3.5-4)
    I reduce my heat at 180* - 190*, depending on bean/profile/charge weight then reduce airflow by 1/3, from 195* -205*, to control temp loss and develop body, 205* is just before the roast starts to heat up again. Airflow is 100% from just before the end of 1st crack ( 205*) until the end of the roast.
    A further reduction in heat down to 50% or as low as 30% occurs about 215*, (give or take once again, depending on the same parameters bean/profile/ charge weight). Heat is turned off just before end temp is reached using bean mass heat to finish the roast.


    Ya learn something everyday!
    Last edited by chokkidog; 30th January 2013 at 11:15 PM. Reason: body comment

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    Quote Originally Posted by Vinitasse View Post
    Actually... Exothermic refers to the RELEASING of heat.... not the production of heat. And since heat is energy and energy must come from somewhere... i.e. from the bean itself... it just makes sense that as the bean loses energy by releasing its heat that it requires more energy input in order to keep the process going. And... by the way... there does happen to be a second exothermic phase following the one you pointed out... it's called Second Crack

    And... just my own humble opinion perhaps but methinks you would be playing silly buggers to challenge Chokkidog on his roasting knowledge
    I'm not challenging his roasting knowledge (I'm definitely a beginner), only his chemistry and thermodynamics (with which I have a little more experience). I apologise if the language came across confrontational; I was writing quickly via the tapatalk app on my phone which makes self editing painfully slow.

    The part about which phase is endo/exothermic I got from https://www.sweetmarias.com/library/...e-degree-roast, which seems to be quite a reliable reference. This reference has a lot more information (in a much less engaging format!).

    Releasing, producing, it's semantics really. And it's not referring to the bean, but to the chemical reactions. The heat is released from the bonds in the chemicals which are broken during the roasting process. The effect is that heat is actually produced within the bean. If the surrounding temperature is higher than that of the bean, then the bean will heat up, otherwise it will release the heat.

    The act of releasing heat does not necessarily mean the bean will cool (as this depends on the relative rates of heat production and heat transfer from the bean); the bean cannot cool at all if the surroundings are kept at a higher temperature (heat can only flow from a higher temperature region to a lower temperature region)

    Anyway, we seem to have digressed. Below is an image of the PID profile used for the roasts last night. While I didn't log the bean temp, it appeared to be lagging 5-10 C below the setpoint temperature in the middile of the roast, and only ever got to about 218C (only a 900W popper).

    Harrar - New.png
    Last edited by MrJack; 30th January 2013 at 11:33 PM.

  10. #10
    Senior Member chokkidog's Avatar
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    Talking

    And then there is the endo / exo reversal point...........
    Thank you Vinitasse for your kind words but I'd be the first person to challenge my roasting knowledge!!
    And I'm more than prepared to eat humble pie. And no MrJack I didn't think you were being confrontational at all.
    But I learnt something else in my reading this evening!.........
    If I hold down the 'option/alt' key on my mac and press zero I can make a degree symbol! 205 ! Voila!
    But I suppose you all knew that too ;-)

  11. #11
    Senior Member chokkidog's Avatar
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    Needs some serious thought this thing about 'endo/exo thermic' conditions in the roast and just how they manifest and influence
    the nature of the roast profile.
    In lay terms, there doesn't seem to be any debate over what the two terms mean; endo=absorbing heat and
    exo=producing heat (and by nature if something is producing heat, it's giving off heat ).
    So if a roast goes from endothermic to exothermic in the immediate lead up to and the start of, 1st crack, then the beans
    are producing heat which is then removed by exhaust airflow, therefore cooling the bean mass at the exothermic reversal point,
    when the beans are no longer producing heat.
    If no changes are made to heat input or airflow then the roast would tend to 'stall' or at least have a decreasing rate of increase.
    A 'lack of exothermic reaction' would mean that the beans retain their heat from endothermic action and the roast wouldn't stall.
    How am I doing? Maybe I wasn't so wrong after all? Is there logic in my thoughts, or should I go to bed?
    I still have a copy of the deleted post if anyone wants to re read it, complete with edited symbols! :-)

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    Re: Harrar Roast Profile

    Sorry, but you've still got it back to front.

    The only way the beans can lose heat to the air (irrespective of what reaction is going on) is if they are hotter than the air.

    So long as you maintain the air temperature greater than the bean temperature then heat will transfer from the air to the beans.

    Now, when the beans are undergoing an endothermic reaction, some of the heat is used to fuel the reaction, instead of heating the beans. If you want to maintain the rise in bean temperature then you need to supply additional heat - equivalent to that consumed by the reaction. Depending on your setup, this could mean a higher temperature, or faster airflow.

    Make sense?
    Last edited by MrJack; 31st January 2013 at 01:05 AM.

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    A very informative discussion - thanks guys. To clarify the whole exo/endo thing. I'm more familiar with the use of the term exothermic in chemistry - the use of the word releasing is ambiguous in this sense, because an exothermic reaction PRODUCES heat/light, therefore the meaning of the word release in this context is "give off" and not "lose".

    Endothermic reactions absorb heat from the environment.

    During the onset of first crack coffee beans are exothermic, a reaction within the bean PRODUCES heat therefore if heat is applied at the same rate from outside (the heat source) the rate of heat gain will accelerate during the exothermic phase and the interval between first crack and second crack would be very short. This is what I expect beans to do, and I usually cut one of the gas rings until the system returns to endothermic, i.e. the bean mass temp starts to dip. Once this happens I relight the 2nd ring and the beans continue to heat steadily up to second crack.

    The Harrar noticeably lacked the exothermic phase that defines first crack - they tended to stall if I reduced the heat as I usually do, and the the snap (energy release) was very soft.
    Ryjoda likes this.

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    Nicely put.

  15. #15
    Life-long Learner DesigningByCoffee's Avatar
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    I've find it helpful to think of these reactions kinda like popcorn…
    Heat em up for a while (endo) then they give it all back in a hurry! (exo). Just that coffee has a two stage process :-) So add heat into that popping stage - and it takes off like a rocket!

    I've found generally that by ramping more heat in just before first crack (from 185 - love that shortcut chokki - save the 'deg' for another day!) can give a stronger reaction - but whether that tastes any good depends on the bean. So don't worry if first crack is quiet - if it tastes good!

    I'm having some great results from this bean at the moment just using my normal gentle ramp profile, which doesn't give an explosive first crack - it just seems to be in the zone for those beans.

    So keep cupping and let us know how they taste!
    Matt

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    Senior Member chokkidog's Avatar
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    Appreciating the informed input to the discussion. Anything that helps my understanding of what is going on
    in the roast is great, not that it's a 'have to know' sort of thing, you can roast just as well without the detail
    but these are the sorts of things I like to get right in my thinking, so thanks.

  17. #17
    enjoy black coffee JamesM's Avatar
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    This coffee can be incredible for any brew method if roasted right

    'habahabanero' nailed it when saying to take it gentle at the beginning. Avoid the tipping and scorching/facing.

    Harrar (in my experience) is outstanding roasted only to "City+" or 'maybe' "Full City". Don't go to 2nd crack. You can achieve "full city" by pulling the roast at the big plume of smoke that hits you just before 2nd crack starts. Watch carefully. "City+" makes for amazing harrar on both manual brew methods AND espresso.

    I enjoyed some recently from a local roaster who roasts this coffee around this profile and it was a real delight in many ways. (except milk, it's horrible with milk in it) Mind you, they have a great deal of experience with this coffee. (always have lots of it!)

    It's going to be difficult to achieve specific profiles with a popper. experiment!

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    Re: Harrar Roast Profile

    Cheers for the input. Interesting that you don't like it with milk (or is it just the city+ roast?)

    I actually have very good profile with my popper - I'm just limited in my max heat input, thus the brick wall at around 218C in our current evening temps.
    The PID controller I use allows me to choose 14 ramp/soak/step settings, and I can watch the profile in real time - if I drag my laptop out to it. Working on a wireless solution to that this weekend.

  19. #19
    enjoy black coffee JamesM's Avatar
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    sounds wild. got photos of your rig? I'm always interested. I have a couple of poppers which I attempt to sample on, but sadly they do not lend themselves to 'light' roasts very well due to uneven roasts.

    I just hate harrar in milk, whatever way it's roasted. Mind you, I've not had it roasted past full city (2nd crack) so maybe once all the fruits and juiciness is burnt off it lends itself to espresso. who knows. I wouldn't torture such a great coffee!

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    Re: Harrar Roast Profile

    I posted one here somewhere.

    See, I love the fruit through milk (which is why I like the Operation Cherry Red at Howard st so much!
    Can't seem to get any blueberry from the Harrar though

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    Life-long Learner DesigningByCoffee's Avatar
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    The fruit cuts really well past soy too - love this one in the white stuff as a change from (or combined with!) chocolate flavours :-)

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    Life-long Learner DesigningByCoffee's Avatar
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    And actually, just following on from one of the little side tracks - doing some typesetting on my Mac, and the proper 'degrees' symbol is actually Option-Shift-8 - so who the heck knows what option-0 is! Can you spot the difference? ?-)

    See grab for real world type application in InDesign… :-)

    Screen shot 2013-01-31 at 2.48.18 PM.png

  23. #23
    enjoy black coffee JamesM's Avatar
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    Quote Originally Posted by MrJack View Post
    I posted one here somewhere.

    See, I love the fruit through milk (which is why I like the Operation Cherry Red at Howard st so much!
    Can't seem to get any blueberry from the Harrar though
    I love the OCR stuff, it's like candy on the dry aroma. Sidamo Guji special prep is my fave.

    Funny, I'm almost certain that last Friday, Trevor (greenman) said he had lost the blueberry notes in his stash of harrar (i think it was harrar).. putting it down to probably just ageing greens. Interesting

    I didn't think Ristretto was running any African coffees at the mo?

  24. #24
    Senior Member chokkidog's Avatar
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    The 'option-0' was from someone using windows, as they called the key ALT.
    Here are the two from my i-mac, just typing into this post :

    option -shift-8........... 205C
    option-0................... 205C

    either is good, yours better, depends on how many fingers you have!

    cheers!

  25. #25
    Life-long Learner DesigningByCoffee's Avatar
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    Quote Originally Posted by chokkidog View Post
    The 'option-0' was from someone using windows, as they called the key ALT.
    Here are the two from my i-mac, just typing into this post :

    option -shift-8........... 205C
    option-0................... 205C

    either is good, yours better, depends on how many fingers you have!

    cheers!
    I've just looked up the two variations in my InDesign glyph set - one is a degree sign - the other a "masculine ordinal indicator!" whatever that is I had a laugh!

    Maybe I should have done latin…

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    Re: Harrar Roast Profile

    Andy's notes on this batch of Harrar mentions it being light on the blueberry. The previous batch sounded very nice.

    I've got some Yemen Banished Ismail I'm keen to ramp roast too.

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    I just completed this roast during the week. I brought it through to second crack it's only going to be used for espresso so it's fairly dark. It's sitting at about CS10 and hopefully it tastes good as an espresso

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    Dumped mine fairly promptly at second crack - about CS10 - very few spots of light oiling. First try this morning - day 4 post roast - almost choked Silvia but didn't have the time to repeat the shot.
    OH THE HARRAR!!! YUK! not a pleasant shot at all, surprisingly charred taste for a roast of this degree, I'm hoping it had more to do with the extraction than the bean/roast, but going by the initial post in this thread I have my doubts.

  29. #29
    enjoy black coffee JamesM's Avatar
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    Harrar Roast Profile

    Damn! 2nd crack can be evil for African coffees! Hehe

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    Quote Originally Posted by habahabanero View Post
    Dumped mine fairly promptly at second crack - about CS10 - very few spots of light oiling. First try this morning - day 4 post roast - almost choked Silvia but didn't have the time to repeat the shot.
    OH THE HARRAR!!! YUK! not a pleasant shot at all, surprisingly charred taste for a roast of this degree, I'm hoping it had more to do with the extraction than the bean/roast, but going by the initial post in this thread I have my doubts.
    The missus couldn't get into the blueberry taste so I thought I'd try taking it to second crack and it was nasty.

    I don't think you can get it to taste better from second crack.....unfortunately.

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    Behmor Coffee Roaster
    This stuff is at it's best when left to rest for at least 14days, IMO.



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