Coffee Roasting     Help with heat management MCR-6

2022-10-22 08:18

Help with heat management MCR-6

I figured it is now time for a post for help/input as I am deep in analysis paralysis mode and wasting too much coffee dialing in profiles.

Recently I roasted a washed Colombian twice for profiling and cupped the next day. I knew from sample roasting that I didn't want to spend too much time in development phase, which means I need a healthy 18-20 degF/min ROR at FC of 375degF to get to my target of 403degF in ~2min.

This was my second roast for this coffee and I was very pleased with the cupping:

RoastPATH - Review

The kicker is that I left the hopper open the entire roast. I figured I should make sure I can repeat that profile since I likely had different convection dynamics (maybe less air going through the drum since the hopper to fan is the path of least resistance).

Here are my next 3 attempts to repeat the roast. You can see the type of firing I had to do to even get close, including bumping the temp mid-roast which I hate to do. I should mention that I have been attempting lower preheats so that I can use less soaking and come in with high heat to step down through the roast, in theory...Typical preheats for these roasts 1800Pa/410degF drum temp/18-22hz on fan. All batches are 6.0lbs and I have been using a drum speed of 58Hz. When I started with this roaster, I tried 54Hz drum speed but picked up a little smokiness/roastiness...this could have been due to fan speed at the time as well though.

RoastPATH - Review

RoastPATH - Review

RoastPATH - Review

These roasts have not been cupped yet and may be OK, but this post is about machine control. I am still having trouble wrapping my head around the proper way to control 6# batches. I tend to think I need to go back to a higher preheat with a longer soak but intuitively I am having trouble making sense of why this is the case. It seems I should get there by firing hard out of the gate.

This roast profile from Bryant is the type of control I would like to have and will give it a shot with this washed Colombian, but why does it make sense that he can soak for so long and then not have to fire hard throughout the roast? Is it because we drive out moisture with latent heat and then need less energy once our bean is drier? Bryant profile:RoastPATH - Review

Any advice or input is appreciated.

Thanks,

Alex LeBlanc

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2022-10-22 14:09

Hi Alex.

Leaving the charging gate open decreased airflow through the drum and exhausted heat through the hopper. Not ideal.

Bryant charged via the drum temp on the machine and probably significantly higher than the BT recorded charge temp.

You write: "I have been attempting lower preheats so that I can use less soaking and come in with high heat to step down through the roast..."

I prefer the highest preheat that the batch and seed will allow without heat defect.

A soak is a matter of preference and seldom used on full batch roasts above 3kg.

My preference is to visualize the roast running on latent heat energy in the roasting system and replenishing it with burner heat throughout the roast. For whatever reason, it seems to work. YMMV

Cup your coffees, preheat higher, soak or don't soak, and maybe extend the roast a little. At your finish temp, you'll probably have better results slowing things down a bit.

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2023-01-07 10:56

Yes, I tend to agree. Some coffees, especially roasted too fast or too dark/too fast tend to taste pretty good on the cupping table 1-2 days post roast, but at a week out, the flavor will tank and coffee is too bitter or not developed appropriately.

It seems for my 6Kg, the sweet spot seems to be hitting FC around 9:15-10:00 for 50% batch size. Coffees are holding on to flavor for over a month and remain sweet and balanced. Of course, varying dry phase and mid phase time have implications for each bean. I only had to waste 100+ pounds to figure this out, chasing every variable except ideal FC start.

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