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Roasting Ethiopian beans on the Gene 101


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Hi All

I'm just looking for a bit of advice or any tips you can give me when roasting these beans.

I have been roasting on the Gene Cafe (Unmodded) for the last couple of months now, and one thing i've found is that I seem to struggle when going for a light roast.

Now this has become more evident recently as I picked myself up a bag of Washed Ethiopian Yirgacheffe beans, and roasted up a light batch. Now after giving them a few days to degas I tried cupping them, and all I can describe the aroma/flavour notes as are grassy, or maybe even like barley.....say an ale for instance (I wanted coffee not a beer 😅), so nothing like the fruity notes I expected.

I just wondered if anyone could shed some light on what I may be doing wrong. It doesn't necessarily have to be for a light roast either, just any advice to get the best roast out of these beans with the Gene.

I log all of my roasts, so i'll try and give as much info as I can:

Weight: 150g

Roast Profile: Light

Roasted indoors at room temperature

Preheated chamber to 210c

Set at 180c for 7 Mins (Dry phase)

Set at 230c for 6 Mins (Until FC, or until I thought I heard FC..... but that's a whole other matter for a different post! 😅)

Set at 225c for 1 min (Development phase) 

Started cooling within chamber for 1 min

Removed and finished cooling outside.

Total roast time = 15 mins (Including cooling)

Any help is appreciated 👍



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Increase your batch capacity to the max you can get 230g iirc for unmodded. You might try 250g.

There's no point in pre-heating to 210c, it doesn't really do much. For a light roast you might be very slightly better for it but the rest of the profile doesn't make sense in that context. The idea being to roast somewhat fast to get the roast developed for a light roast. Pre-heating can help get heat into the beans a little quicker but holding at 180c for 7 minutes is illogical if that's your aim.

The set temp on the gene doesn't really give enough info. When you say you set at 180c for 7 minutes does that mean the temp was 180c for 7 minutes or that the temp increased and may not have reached 180c in 7 minutes? Same for the other stages, a setting of 230c doesn't mean that's what temp you reach. 

Do you see burning/scorching if you just let the gene heat up without the 180c stall? If not don't bother with the step. The beans dry through the whole roast, though <160c is generally referred to as a 'drying phase'. After 160c you're into maillard, extending here before first crack will give you meaty/savoury flavours and imo the shortcoming of the gene is it's very difficult to alter the length of time this stage lasts for.

IMO you are best putting as much energy into the beans as you can without burning/scorching. Pre-heating shaves about 30 seconds off the drying phase but has no real affect on the rest of the roast. It looks like you want a fast, light roast which requires a lot of heat early on to get development but the gene isn't good at this, even with a pre-heat. I would drop the 180c stage and try to extend development to two minutes without going into territory where you'd taste roast notes. The colour shouldn't change very quickly, if it does you might drop the 230c to 225c and 225c to 220c, though this might stop you from reaching first crack in a reasonable time. With a dimmer you'd just reduce power a bit more and solve the problem that way. Changing 225c to 220c by itself I think would risk crashing the roast.

So first things first, increase batch to the normal full capacity of the roaster.

Then drop the 180c see if there's burning or scorching, if there is I don't know what to say. Maybe try a 200c limit instead. 



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Hi @Rob1

Sorry, I wasn't very specific there. The "Set temp" times that I mentioned related to me setting the temp and then allowing it to climb to said temp until that "Phase" had finished (e.g after drying phase, i'd set the temp to 230c and allow the Gene to climb and reach, then hold at that temp until FC). This is one reason why I would like to do the dimmer mod on the Gene, to allow me more control, however with it being fairly new I don't fancy voiding the warranty just yet 😅.

I am planning on doing a roast today at some point, and from what you've said, this will be my plan of action....along with my understanding as to why, so please let me know if i'm wrong: 

  1. Increase batch size to 230g (This will help maintain temp within chamber?)
  2. Do away with the preheat (Waste of time and energy if I do a dry phase?)
  3. Set at 160c until yellowing (This one had me thinking, whether to skip the initial dry phase like you said, and just push it into Maillard temps, say 200c off the bat, or will it have an adverse effect on taste? or to have the initial dry phase then increase to 220c as per next step?)
  4. Increase to 220c until FC (I usually crank it up to 230c but wondering if that is too high for these beans?)
  5. Drop down to 215c for 2 mins for Development 

Let me know what you think, and thanks for your input, I think you may be onto something.....but I think this has left me with more questions 😅, but i'll see how I get on and keep you posted. 👍



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4 hours ago, JCUK said:


  1. Increase batch size to 230g (This will help maintain temp within chamber?)
  2. Do away with the preheat (Waste of time and energy if I do a dry phase?)
  3. Set at 160c until yellowing (This one had me thinking, whether to skip the initial dry phase like you said, and just push it into Maillard temps, say 200c off the bat, or will it have an adverse effect on taste? or to have the initial dry phase then increase to 220c as per next step?)
  4. Increase to 220c until FC (I usually crank it up to 230c but wondering if that is too high for these beans?)
  5. Drop down to 215c for 2 mins for Development 


So when does first crack occur? From what I know now you set the machine to 230c and it cycle up to that temp and holds there for 6 minutes....but that doesn't really give any indication of when you get to first crack. Time of bean colour changes, reading of temp at these changes, and also first crack time and duration would go some way to explaining the profile...


1. To help trap energy, so yes.

2. Kind of. If you're roasting back to back pre-heating to 60c can make sense, otherwise it has little impact on the roast beyond a shorter drying time and possibly slightly better early development but it won't always be necessary to do get that (bean dependent) and it's bad for the roaster. 

3. No, that wouldn't be good. I said don't bother with the drying phase. "Then drop the 180c see if there's burning or scorching, if there is I don't know what to say. Maybe try a 200c limit instead." As in just run it at 230c straight away and if there's burning or scorching try 200c instead of 180c. Change settings based on colour changes and roast defects, if colour is yellow-brown you'll want to be above 200c on the readout. 

4. I don't know, if you see burning and scorching at that temp then maybe it is too high. 235c might be better, it depends how your roast is progressing and if you see burning.

5. This is based on a 5c drop from the set temp. I don't know if you'd even hit first crack in a reasonable time with a setting of 220c. I didn't mention 215c...

re: the 'drying phase at 160c' I think there may have been some confusion. I was referring to the bean temperature not the temperature on the gene readout. 

Edited by Rob1
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Hi Rob

Sorry for the late reply, I've not had chance to get online over the weekend.

I did however do another roast on Friday, and this is what I logged:

Did NOT Pre-heat.

  1. Increased the batch size to 240g
  2. I set the temp to 190c for dry phase, which lasted for 7 mins until yellowing occurred. (I know you said to do away with this, but I had scorching the last time I set the temp higher, so thought i'd find a middle ground)
  3. Bumped the temp up to 230c until FC, which happened at 14 min (Not sure on duration as I lowered the temp as soon as I heard it)
  4. Lowered the temp to 225c and allowed it do develop for 2 mins.
  5. Started cooling within the chamber for 1.5 mins, then finished cooling outside.

This led to an overall roast time of 16.5 minutes. 

Here's a photo of how they turned out. Now the beans look OK I guess, though I can see that there are some areas on the bean that appear darker, and some even shriveled.

I'm thinking I may have dropped the temp too early at the start of FC? Does development time include rolling crack or should I have say given it 30 seconds, then started timing?

I'm going to give them another day to degas, then give them a try.EthYirg.thumb.jpg.6d91b2f839faabb830b43349a6778607.jpg

Thanks again for your help.


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14.5 minutes can be a good roast time, obviously you have to judge it by taste. 

If you're seeing scorching early in the roast around yellowing and yellow-to-brown development that's unusual. Maybe unless the beans are old or low in moisture. 

Some of the beans are a little puffed up and there seems to be a bit of scorching there. With the unmodded Gene I'm not sure there's a way around this by due to the design. The scorching will usually occur after first crack. 

If you crack the beans in half do they look to be a consistent colour outside in?


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Just cupped the beans from the last batch, and they are still a bit grassy, however I could taste and smell some fruity undertones so i'm getting close 😅

I still think they were a bit underdeveloped as I wasn't able to break a few beans between my fingers, but those that I could crack did seem consistent with the outside.

I think you're right with regards to roast time so i'm going to try and reduce it. I've got enough beans for one more batch so i'm thinking:

No Pre-Heat 

230g Batch

1. Set at 210c until yellowing

2. Bump up to 230 until FC

3. Allow rolling crack for 30 seconds (I think I reduced temp too quickly last roast)

4. Reduce temp down to 225c for 1.5 mins for development

5. Start cooling

I'm hoping by setting a higher temp to begin with and allowing a rolling crack before dropping the temp, it will bring down the total roast time by a minute or so. Also am I right in thinking the second phase up to FC should be quicker than the dry phase? as looking back at my log they both lasted 7 minutes. Now surely dry phase takes longer because its reducing moisture content?

Hopefully going to try and do the roast tomorrow. I'll let you know how it turns out 👍

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From memory the gene might take about 5 minutes to heat beans to 145-150c and it might be 6-7 minutes from the point they start to yellow until first crack.

Moisture content is reduced throughout the entire roast. How long it takes to go through each phase depends on the temperature you're using. 

You might find you don't need to lower the temperature at all. I've had one bean that just took full power all the way through without taking off until into second crack but the roast would have ended before then. If the roast isn't going into first crack with enough energy you need to put more energy in sooner, especially since you appear to be getting some negative effects from high temps even at 230c. More heat early in the roast=more heat into the inside of the bean=more energy into first crack.

1. This seems more reasonable but if you don't get scorching in the early phase of the roast I'd use as much heat as I could. Exception would be with a chaffy bean like a natural brazilan. 

2. Ok.

3. 30 seconds after rolling can work, it depends how quickly the roast is progressing. If you want a light roast 30 seconds after rolling is probably going to be too late, especially if you are going to keep it developing for 1.5 minutes. You're probably looking at medium to medium-dark here.

4. Ok. Careful not to stall the roast if it's not progressing through first crack with any  real speed.

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Hey Rob

Last update, I promise 😅.

I used up the last of the beans on Thursday, and it turned out pretty well (Compared to previous roasts). These are the steps I took:

Batch size = 230g

No Pre-heat

1. Set temp to 210c until yellowing (Took 7 Min)

2. Increased temp to 235c until FC (Took a further 6 Min)

3. Allowed 30 sec rolling crack at 235c

4. Brought temp down to 230c for 2 mins for development

5. Started cooling within chamber for 1.5 min

6. Finished cooling outside

I went for a medium roast this time and it seems fairly even, and i'm not getting that grassy smell or taste anymore. I even made a coffee with them this morning, and it didn't taste like ale!

You were spot on with the timings as it still took around 7 min to start yellowing, and a further 6 min until FC. But once it reached FC it progressed nicely and I could hear the cracks all the way through to the development stage, unlike last time when cracking stopped as soon as I turned the temp down.

I think you're right with regards to temp aswell, and if/when I do get some more beans i'm going to try and increase the temp some more and maybe even hold it at that throughout FC and development and see how it turns out.

Anyway, here's how they turned out:


Thanks again for your help 👍





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  • 1 month later...

This is my Ethiopia beans. I do preheat at 150 for 3minute and drop with 210gram set 14minute 240c, 4minute cooling inside till 150c before take off the beans. Result, i am happy with that. 
i think somehow after FC but before SC. I used exhaust temp. 


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