Patchy Roast

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Patchy Roast

Postby Tristan » Tue Mar 10, 2009 10:09 am

Hey guys. What would cause a roast to produce patchy, marbled, mottled, uneven colour coffee.

Too little coffee?
Too high initial temp burst?

Or is this just a trait of home roasting?
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RE: Patchy Roast

Postby syscrusher » Tue Mar 10, 2009 11:00 am

Could be the beans. Anytime I've roasted a Harrar for example it tends to be uneven.

It could also be your roaster applying the heat unevenly - what are you roasting on?
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RE: Patchy Roast

Postby CakeBoy » Tue Mar 10, 2009 11:02 am

What did you use to roast Tris?
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RE: Patchy Roast

Postby Tristan » Tue Mar 10, 2009 11:17 am

Gene cafe roasting gethumbwini...
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Postby radish » Tue Mar 10, 2009 11:20 am

My last but one roast was a little patchy as well (using a Gene Cafe). I have a voltage meter and I noticed the current was fluctuating throughout the roast, so I put it down to that. My last roast was fine (with a stable voltage).
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Postby CakeBoy » Tue Mar 10, 2009 11:30 am

Most of of our Gene roasts were even. We did notice that Geth was a little less uniform even in the Pinhalense, so it could be the bean type. Steve or Anette will prolly come and tell us why in a bit - harder beans I expect :)
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Postby kingseven » Tue Mar 10, 2009 3:17 pm

I would guess - without knowing the profile - that it is a drying issue with that portion of the roast. Was first crack quite long and drawn out? It is a very dense coffee which makes even drying before maillards really kick in a bit trickier.
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Postby Tristan » Tue Mar 10, 2009 10:02 pm

First crack always seems to be long and drawn out! Got it with me, will show you tomorrow.
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Postby espressomattic » Tue Mar 10, 2009 11:30 pm

I've roasted Geth quite often and it needs a longer roast than others. Ideally I would give it a ramp in temp right after 1C, but that isn't possible with my Gene. I have similar issues with Tierra Linda and also Kalosi.

I have to stretch it as far as I can and get there in the end...usually.
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Postby ivdp » Wed Mar 11, 2009 9:49 am

If roast is marbled etc, than I would presume that coffee is not yet ready, so under roasted.
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Postby Beanie » Wed Mar 11, 2009 10:49 pm

Hmmm... pics? :)
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Postby JulieJayne » Sun Mar 15, 2009 9:52 pm

How much did you put in the roaster. I have noticed with the Gene that if it is overloaded, then the roast can be patchy, insufficient airflow I guess. Highly chaffy coffees can cause this with a smaller load, as the chaff restricts the airflow.
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Postby Tristan » Mon Mar 16, 2009 7:55 am

I'll get a picture up soon.

I showed Jim Hoffmann and he concluded that being such a hard bean they needed a longer warmup to 1C and that in general roasting hard beans at home is pretty tough. The other problem with the gene cafe is that you can't load into a hot drum as you have to stop the cycle and remove it.

It was 125g of green.
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Postby JulieJayne » Mon Mar 23, 2009 6:27 pm

Tristan wrote:The other problem with the gene cafe is that you can't load into a hot drum as you have to stop the cycle and remove it.

Well you can do an emergency stop, then using oven gloves remove the drum and load the beans. You can then start the cycle at over 100C

Tristan wrote:It was 125g of green. I showed Jim Hoffmann and he concluded that being such a hard bean they needed a longer warmup to 1C and that in general roasting hard beans at home is pretty tough.

But if you need a longer warmup then loading into a hot drum is surely going the wrong direction.

And I find it much easier and consitent to always roast at max capacity, or very near, I rarely roast less than 300g unless it is a chaffy coffee.
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Postby espressomattic » Mon Mar 23, 2009 6:52 pm

I have noticed this mottling with my current Colombian CoE.

The first few roast were pretty even and the beans were very even, however the past few have what you have described. Nothing changed really whether it was 150g or 200g. What has changed though is the temprature here as it has got a little colder, but I can't see that affecting it as the beans are stored in the basement garage which is pretty warm.

I have tried pre heat with these and thinking about it, that made a difference. Damn, why didn't I see that :?

Ah well...
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