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Thread: What criteria to monitor in roasting?

  1. #1
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    What criteria to monitor in roasting?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I know Ive read this somewhere but cant recall the detail and cant find the posts that I remember.

    As a newbie who has only done his first roast this morning Ive made copious notes and have a profile of what Ive done. The things that Im monitoring apart from the temperature profile of the roast is the ambient temp, bean weight loss during roasting, time of first and second crack. Somehow I didnt hear the first crack; at least I hope so because Im assuming that at 16 30" the cracks I did hear were those of the second crack.

    My question really is about how important the weight loss during roasting is. My first effort resulted in a 20.8% weight loss (250gm initial weight). Should I be trying to aim for a particular percentage? Should I aim for consistency roast to roast? If it matters, Im using a Gene Cafe.

    Any help for a newbie would be very much appreciated.

    Thanks in anticipation.

  2. #2
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    Re: What criteria to monitor in roasting?

    I think consistency between roasts for a given bean variety and batch size is important, it helps define and set consistency in other variables you choose.

  3. #3
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    Re: What criteria to monitor in roasting?

    Not having used a Gene let me answer from my own experience.

    I take note of:
    Batch size (usually 600g in my case)
    Bean
    Ambient temp (at the start)
    Temp at 1 minute intervals
    Time of First Crack start and finish
    Time of Second Crack (if I go that far)
    Time roast pulled
    Final weight (to calculate percentage of moisture loss)
    Time cooling starts

    Quote Originally Posted by 727B667671672121140 link=1272084910/0#0 date=1272084910
    Should I aim for consistency roast to roast?
    Mostly.
    Firstly, if your roasts are palatable, try to be consistent in order to learn to be consistent.
    After that, you can change one thing at a time to see if you prefer the taste that change makes. e.g. roast a little darker or lighter.


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    Re: What criteria to monitor in roasting?

    Thanks very much for this. My first attempts have been with a blend supplied by Chris at Talk Coffee. I figured that I would start with this as Chris also supplied some of his roasted beans of that blend and I can compare my results with his. While I dont intend to blend green beans in the future the fact that I am at the moment leads me to ask if different bean types crack at different temperatures? I ask this because Im having difficulty in hearing the cracks and Im guessing that what might be part of the reason is that the beans are cracking at different times thereby reducing the intensity of the noise they make. Could I be right?

    I havent made an appointment with the audiologist yet as I understand that the noise of the Gene Cafe operation does make it difficult for novice roasters to work out what they are hearing.

  5. #5
    KJM
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    Re: What criteria to monitor in roasting?

    Since I use a Gene Café too, let me chime in with some random observations.

    I think 20.8% loss might be a little high. Of course, this depends on how accurate your measurements are - 2.5g is 1%! It also sounds like youre taking things into second crack, which can be a tiny bit overdone in the Gene because of the slow way it cools.

    Ill just tell you how I do mine right now (which is different from the way I used to roast in the Gene because my Gene started to behave differently one day....).

    I pre-heat the chamber to 250C (max). This is a good test for a Gene, BTW, it should take 5 to 7 minutes.

    Emergency stop, put the chamber in the stand (BEING CAREFUL ABOUT HOT THINGS....). Dump in my 250g of beans. I whack it back in the machine and set the timer. For simplicity - set it to 20mins.

    The beans should enter 1st crack between 9 and 10 minutes later (so 11:00 --> 10:00 on the display). I get them to rolling first crack and then turn the heat down - in my case to 228C. The actual times will vary a bit, due to ambient temperature. Yesterday, it was 18C and the first snaps of FC came at 9:30 elapsed. On hot days in summer, it might be just under 9.

    I then roast to the depth I want. For me, this is usually 3 to 4 minutes after the END of FC. Which is about 30 seconds to 1 minute BEFORE the onset of second. Depending on the beans, this gives me 15->18% loss. I use the emergency stop mechanism and dump them into an external bean cooler, put the chamber back in, spin the timer knob and press the heat knob twice to set the Gene into its cooling mode.

    There has been some bumpf posted about using the emergency stop mechanism being bad for the life of the roaster. If you take it to bits, youll quickly see that this is clearly not the case. But you do want the cooling cycle to be activated and not let the thing "heat soak" cool. Which would be bad...

    The external cooler is nothing more (at present) than a 10" exhaust fan with a 10" Tami (a stainless circular fine sieve that French cooks use). It cools to room temp in less than a minute in summer and in about 30 seconds in winter.

    Now, weight loss depends on how you store the green beans too. Mine are stored in plastic tubs in a cellar - so the moisture content is pretty stable. The process in the Gene is basically 100% repeatable for me and for at least two other Gene owners that Ive passed it on to. It enables you to be really consistent....

    So: with all that in mind. I actually DONT monitor things so closely anymore (despite the Engineer in me slightly wanting to..). The only two input variables for me are ambient temperature and weight of beans. The weight I deal with by weighing ;D and there is nothing I can do about ambient. Changes in ambient just alter the point I turn the wick down at.

    Of course, the above applies to hard beans, if you have softer beans you can set the initial heat lower to avoid tipping and/or case-hardening!

    As I said, at least 2 other local roasters use exactly this approach with excellent repeatable success.

    Hope it helps! It is all good fun anyway, and it is the result in the cup that counts! How you get there doesnt really matter at all...

    Cheers
    /Kevin

  6. #6
    KJM
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    Re: What criteria to monitor in roasting?

    Quote Originally Posted by 4B425F4F485E18182D0 link=1272084910/3#3 date=1272168499
    Thanks very much for this. *My first attempts have been with a blend supplied by Chris at Talk Coffee. *I figured that I would start with this as Chris also supplied some of his roasted beans of that blend and I can compare my results with his. *While I dont intend to blend green beans in the future the fact that I am at the moment leads me to ask if different bean types crack at different temperatures? *I ask this because Im having difficulty in hearing the cracks and Im guessing that what might be part of the reason is that the beans are cracking at different times thereby reducing the intensity of the noise they make. *Could I be right?

    I havent made an appointment with the audiologist yet as I understand that the noise of the Gene Cafe operation does make it difficult for novice roasters to work out what they are hearing.
    Our posts crossed during the typing! Yes - different beans will go at slightly different points. If you rote follow what I suggested above, you only need to listen closely during a 1 minute or so period. The swelling of the beans is also a cue.

    Ive been roasting blends just lately - some of which have substantial amounts of "soft" beans. It still works just fine but it does spread the pops a fair bit. A single origin will snap and pop a bit then really hit the straps then go quiet pretty quick. My recent blends tend to start and have an extended medium intensity snap session (rolling FC).

    Cheers
    /Kevin

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    Re: What criteria to monitor in roasting?

    Thanks Kevin. Ill persist with letting the Gene Cafe manage the process till I get more confident then Ill try your pre-heat and external cool-down process as two additional variables to try. My first roast was certainly too dark and while Im not going to jump too quickly to make a judgement about the palatability until they have rested for a while I think they might ultimately make their way to the bin. Ive now done two additional roasts, one where Ive shortened the duration and one where Ive cut the temp. I cant wait till I can make a reasonable judgement by taste of the results. Visually they have had very different results.

    Thanks for your observations.

    Larry

  8. #8
    KJM
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    Re: What criteria to monitor in roasting?

    The problem with the Gene is basically that it doesnt stop the roast quickly enough. So when you hit stop, it doesnt cool so quickly... If you get to second crack, then it continues for something like 20seconds or so. That can be a real problem!

    The recipe I posted above reliably hits first crack for mine and three other local roasters at the same time. I was pointing at this so youd be able to dial in on the sounds of first crack! While the Gene is loud(ish), the pops are very clear to me.

    The other thing to bear in mind with the Gene is that it doesnt recycle any hot air. So that makes it heat up more slowly than other roasters. The nett result is that from cold, it can take a long time to do a roast. Some observe that this gives a "baked" kind of taste to the beans. My personal observation is that the start from HOT (preheat) gives a very noticeable improvement in taste.

    Kalgoorlie eh? Surely you could just use 1 sheet of corro iron and sprinkle the beans on top in summer. Although, come to think of it, that might get to FC a bit too fast ::)

    Cheers
    /Kevin

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    Re: What criteria to monitor in roasting?

    That would work in summer here but in winter we have some mornings that are down to minus zero which would delay first crack somewhat if it was a solar-based process. The joys of inland living.

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    Re: What criteria to monitor in roasting?

    Ive just had another roasting session this afternoon following Kevins directions. There wasnt as much drama in managing a hot chamber as Id imagined there would be. My warm-up time was 6 28" and I was probably being a bit too cautious and could have worked faster as the temp had dropped to 190 deg C by the time I got the Gene working again. A very distinct first crack was heard at 9 29" into the roast at the same time as I got the first puffs of smoke. At 9 45" I dropped the temp to 228 as Kevin suggested. Im not sure if the beans got to second crack as I couldnt hear one but I ended up pulling the beans at 13 and cooled them down outside of the Gene as Kevin suggested. My cooldown process simply involved moving them from collander to collander in the relatively cool breeze that is present today. Ambient temp 22.3 deg C. Weight loss 15.2% and a paler result than my previous roasts. Now to wait for a rest period and a taste.

    Thanks very much Kevin for your advice. Ill let you know how they taste.

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    Re: What criteria to monitor in roasting?

    I use a Gene and so similar to Kevin, but slightly different:

    Always use 250gm

    Preheat chamber to 100-200 degrees then hit cool cycle. That takes it down to 60. I believe the actual temperature you start with is not important by itself, BUT, if you want to be able to do back to back roasts (I do 3) then you start from the same point.

    I run flat out to FC (usually around 10-11 minutes), then down to 235 to where I want them. Stop the roast slightly before desired point and press cool and let it go all the way (dont have a cooler). I monitor stopping point by colour, but should be around 15 minutes.

    Finished roast will usually end up weighing between 207 gm (dark) and 210 gm (light) so thats between 15% and 18% loss.

    I generally do 2 batches Brazil roasted to CS8 and 1 Indian Monsoon to CS9.5, let cool and blend. This gives me 610gm coffee which lasts 3+ weeks.

  12. #12
    KJM
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    Re: What criteria to monitor in roasting?

    Well LF - you heard the pops of first crack then! Good. That was basically the goal of my suggestion. The lighter profile roast will make it a slightly more acidic brew. So youll need to leave it longer to mellow. The darker roast depths permit earlier drinking (he says, HUGELY simplifying a very complex subject....).

    Second crack is harder to pick. If you let it go longer, youll start to get a "second wind" in the smoke department and the aroma of the smoke will have a decidedly sweeter note to it. That means second is coming. The noise from second crack is widely described like crinkling cellophane. Unfortunately with the noise from the Gene, it is a bit hard to hear. It is actually worth taking a roast there (even if you dont really want to) to hear/smell it.

    The other thing I mentioned in passing was hard beans versus soft beans. This has everything to do with where they are grown and basically high-grown beans are "hard".

    Hard beans respond well to (relatively) brutal heat injection... Softies dont. Theyll heat unevenly and youll end up with burnt tips. Id highly recommend you peck "roasting defects pictorial" into Google and the Home Barista posting will be #1 or #2. A fabulous resource - the pictures are worth a thousand words.

    The Gene is not like a commercial roaster - it is like all the domestic roasters - hamstrung by insufficient heating capability. The heat-like-stink trick to get to first crack quickly is just one way of dealing with that restriction. The designer was quite sensible in making sure the heater fan continues to run when you hit emergency stop, so the trick works just fine and interior of the machine doesnt get hot as a consequence of hitting the red button. The other thing to note is that the roasting chamber and particularly the metal plate act as heaters for the beans.

    The Gene is a great roaster, youll have a ball and get terrific results. It just comes down to finding a process that suits you.

    Cheers
    /Kevin

  13. #13
    KJM
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    Re: What criteria to monitor in roasting?

    Quote Originally Posted by 727B667671672121140 link=1272084910/9#9 date=1272257913
    *Now to wait for a rest period and a taste.

    Thanks very much Kevin for your advice. *Ill let you know how they taste.
    OK, so how do they taste?? Given that you did this on the 26th, and I couldnt possibly wait any longer to taste if it were me ::) Im dying to know how you got on!

    The roast should be lighter than your first, so will be slightly more acidic and need a longer rest (probably). But you should be OK to dive in for a try by now!!

    (Im going fishing for 10 days on Wednesday, so this is almost my last chance to hear how it went till later in May!!).

    Cheers
    /Kevin

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    Re: What criteria to monitor in roasting?

    You are absolutely right: I couldnt wait! The first roast was -- well -- unpalatable and after trying twice over several days made its way to the bin. Ive been drinking roast number 2 which I think was roasted a little too dark for the last week and it is certainly drinkable. You have to remember that I live in a place where getting recently roasted beans is very difficult so my standards are very easily challenged. Roast number three was using Kevins methodology but I think I pulled them too early at 13 mins and they were significantly paler. I use an Aeropress at work and these are ideal for that. Ive been enjoying these all week.

    This weekend Ive been roasting again using Kevins strategy and cant wait to try these. I took them both to the beginnings of second crack. I did some PNG Waghi AA and some more of the green blend that Chris at Talk Coffee supplied. The green blend came out popping. They look really good and I cant stop sniffing them.

    I was amazed by the differences in the size of the beans between the PNG Waghi and Chriss "Shed Shandy" blend.

    I now have tons of questions which Ill spread out a bit. The first and most weighing on my mind is what you mean by hard beans and soft beans. Is this a result of the processing or a basic property of Arabica or Robusta beans. or even something that comes from where they are grown? I seem to find it difficult on the web to find enough information about what bean types, processing methods are used in the bean names being sold. Take my PNG Waghi beans. I cant seem to find if they are Arabica or Robusta beans and it doesnt seem obvious (at least to me) what processing methods have been used. Are they hard or soft?

    Any info would be appreciated!

  15. #15
    KJM
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    Re: What criteria to monitor in roasting?

    Glad youre finding it interesting!!

    There is nothing like your own personal experience with roasting to settle on how dark you take a roast. One thing that people often suggest is roasting the same way, but taking the roast a tiny bit darker. You then have your own brain cells trained on what making that particular bean darker tastes like. The other interesting thing is roasting for milk based or espresso. You need more acidity to get through the milk, and by going a tiny bit lighter you can get that, for example, but it isnt quite that simple!

    PNG Waghi beans are one of my staples - I love the slightly caramel/malt/spice hint you get with PNG beans. Mal has posted some absolutely spot-on advice about PNG beans in general elsewhere on the forum. Ive personally found amazing results with Waghi by roasting almost to second crack, and then blending that with Waghi taken a bit lighter.

    The Arabica/Robusta thing is basically just two different species of coffee. The Robusta is the one that has significantly more caffeine in it and many would argue (me included) a heck of a lot less interesting taste. More your 43-beans-in-a-cup kind of taste. But it is used a constituent in some blends. The PNG beans are arabicas, as are 99% of the beans youll buy in beanbay! Unless it says Robusta, it is arabica!

    The soft/hard thing is basically about how/where the beans are grown. Generally speaking, high-grown beans are hard. Again, generally speaking African beans tend to be hard. Beans which you might expect to be soft beans because of their origin but are hard often have SHB added to the end of the name or explicitly add "high grown" or something like that. Soft beans, by and large, need a slightly gentler heating profile, as has been already said.

    Now, just to muddy the waters even more - you also get dry processed and (surprise!) wet processed beans. This refers to the way the pulpy bits are removed from the beans. Generally speaking, dry processed leaves a better mouthfeel on an espresso (think: "thicker").

    Im definitely no expert - the real experts can chip in and add/correct the above, but thats the kind of things I work with now. Ive been playing around blending some greens and roasting them together (because Im being lazy!). The hard/soft thing initially caused me problems - I thought the soft Brazilian base I had chosen would get over-done (theyre soft). But it turns out not to be so. I assume the other (hard) beans in the blend somewhat buffer the heating. I also like to include dry processed beans (the Brazilians, for example, are washed) to lift the mouth feel (I drink espressos as well as lattés!).

    The engineer in me wishes there was some kind of simple guide to all this, but it seems that it is way more complex than can be automated! Roasting is an interesting journey - and you can only reference the goodness-of-fit to your own palate. The kind of coffee I roast most people like - but thats because I roast stuff that people will like. My personal choices - Yemeni and Ethiopians are not to everyones taste so I enjoy those alone!

    No better way to learn than (1) doing it and (2) reading these forums!

    Cheers
    /Kevin

  16. #16
    KJM
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    Re: What criteria to monitor in roasting?

    Hey LF - I just got back from my 14 days of restful fishing.... Im wondering how the roasting journey is going?

    /Kevin

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    Re: What criteria to monitor in roasting?

    Ive also been away for over a week so Ive not reported on my learning curve. My biggest problem is that Im not drinking coffee fast enough to use up the beans so that I can play with the roasting varialbles as much as Id like. Ive now roasted enough times to be confident about the process and Ive developed a methodology that is now pretty standardised and delivers a predictable result. Ive predominantly been roasting PNG Waghi AA but Ive been working through the bean types that I got in my starter pack from beanbay. To be honest Ive found that a bit frustrating as the amounts that the starter pack includes alllows for only two roasts and that isnt really enough to do more than get a taste of the beans with a typical roast profile. I think Ill stick with PNG Waghi and experiment but now that Ive read more about bean types Im going to purchase some robusta beans and see what they might do to the flavour of the PNG Waghi beans if blended in a bit.

    There is so much to try out!

  18. #18
    KJM
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    Re: What criteria to monitor in roasting?

    Behmor Coffee Roaster
    Ahhh! I feel for you! Mrs-KJM was the only other coffee drinker when I started roasting, and only somewhat grudgingly at that. Since then, however, my daughters (the youngest is 18.9 - birthday in a couple of days!) have grown up into coffee drinking. I also take some beans into work and a couple of us have a nice coffee....

    Helps the consumption rate enough that some weeks I manage to run low!

    Ahhh. The joys of making the roasting rate = consumption rate!

    /Kevin



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