Coffee Roasting     Advice on Roasting Burundi

2020-11-22 23:21

Advice on Roasting Burundi

hello

I'm having trouble preventing ROR collapse during first crack when roasting this washed Burundi. Link to the roast profile is attached. Hopefully the link works. Unfortunately RP didn't record the air and temp changes, which would be extremely helpful.

I'm roasting on an older (circa 2014) Mill City 1kg roaster using propane. This particular roast is an 800gr batch. Charge temp was 370F, air was a 30hz, 3.4kpa after 1 minute soak. Air and gas were at 40Hz and 2.0kpa, respectively before FC.

I'm thinking I'm coming into FC with too much heat. So I will reduce the heat the heat prior to FC on the next roast. Hopefully the roast will not stall in FC.

All advice is greatly appreciated. Again, sorry for the lack of data.

Tal

https://portal.roastpath.com/publicroasts/index/1193217272700221120

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2020-11-23 16:43

Hey Tal,

Each week I bring a few of these types of questions to Derek and type up his thoughts - I'll shoot this one to him tomorrow or Wednesday and see what he thinks.

-Lauren

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2020-11-23 23:25

Lauren

Really appreciate it.

Cheers

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2020-11-25 12:13

Hi Tal!

I brought this question and your roast curve to Derek and we chatted about what might be going on. Here are some of his thoughts:

First, your roast isn't crashing. You are seeing a decreased ROR at FC, but your roast has a lot of energy and it looks good overall. It never stalls out, because it never stops (Derek used the analogy of a California rolling stop, your ROR rolled this stop sign - it didn't stop and wait, if it had you would have seen a negative number for your ROR).

Your phases look good. 5:30 in dry phase, 4 mins in mid, 3 mins in development, that's a standard roast curve. If you're looking for more brightness in this Burundi, think about shortening your dry phase by about 30 seconds. You could achieve that by simply shortening your soak, going for 30 seconds rather than one minute.

The sharp decrease in your ROR is likely more about your thermocouple than the actual heat in your roaster. Derek suggested making an earlier air adjustment to try to gradually increase air in your system rather than only one adjustment at FC. That might look like air @ 30hz at charge, then 40 at dry end, then 50 at 9 mins (if you adjusted your profile by 30 seconds based on the recommendation above).

Overall, we're missing a little bit of information in your summary. The hertz reading on your air speed is only meaningful to you, we can't know how much air that is. Using the lighter trick, you can identify a low, medium, and high air flow number then include that in your description (i.e. low air at start, then air to medium at first crack). We also don't know what your max gas is, if you can find that out you can include a percentage for your gas settings (i.e. fuel to 3.4kPa, which is 75% of my max). Information like this will help other roasters calibrate to your settings.

Lastly, how did this coffee taste? What matters most is in the cup. Derek thinks you have a good profile here, but only you can know if there's something you want to change, and you decide that at the cupping table. He also brought up the laws of thermodynamics, which he's been thinking about a lot lately: heat energy has to go somewhere in your roaster, it doesn't disappear. You coffee is still taking on energy at the end of the roast, not losing it. Check out Candice Madison's article on thermodynamics in this month's issue of Roast Magazine to learn more, and join Derek in trying to totally disprove the myth of the crashing roast.

Thanks for the question! Let us know how the next roasts go.

-Lauren

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2020-11-29 17:29

Lauren

Thanks for getting back to me, and glad to see Dereck's positive feedback. Please thank Derek for me. The cup is actually good - chocolate tones, good development.

The max gas on my machine is around 5.0kpa. So, 3.4kpa is around 68% max. Seems odd. As far as airflow, I generally start at 20% (low), 30% at or soon after dry, and 40% -50% just before FC. The last airflow change depends on the bean. As I mentioned for some reason RP didn't record the gas/air changes. Maybe user error. I'll pay closer attention next time

This Burundi was left over I was using for experimentation. Now, I'm curious about Derek's suggestion to use a shorter soak. Great idea. Not sure why I didn't think of it (duh!) So I bought more of the same beans to see how a shorter soak changes the cup.

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