Coffee Roasting Full batch sizes
@raccroasters
Posted in Coffee Roasting
Full batch sizes
Hi all,
Running an MCR-2D on propane, max gas 3.2 kpa, currently at 45 Hz for 68 RPM.
I had some questions on the batch size. I feel like for a lot of my beans I can't go full batch size without slowing things down a lot.
Charging right now at 440 on the PID which, to me anyways, feels quite high and still getting G2Y at 5:30 ish with max gas. FC usually happens for me between 9:30 and 10:30 depending on the bean (with 2 kg charge) and for some Bourbons it's fine, but for others the end cup quality would benefit from a faster roast.
I've tried charging higher to save on a few seconds and ended up with tipping and other roast defects. So feels like I'm between a rock and a hard place, slower roast with all that it implies, or roast defect on the other end.
Most people I've asked in this and other forums, and the vast majority of profiles that are public on roast path do not do anywhere close to a full charge on the MCR-2D and the ones that do, such as https://portal.roastpath.com/publicroasts/index/2198936415217040821 (over full charge) I can't seem to replicate at all using similar gas (changes, not levels, starting much much much higher) and air changes. I tried with really dense beans charging at 2.3 and ended up close to 14 minutes to reach that end temp. With the gas I don't even understand it since propane has more energy than natural gas and I'm doing 50% higher KPAs (3 on mine vs 2 on theirs)
The way I've found that works for me is just to reduce the charge weight by 25% to about 1.5 Kg, but that means 25% more roasts to reach the amount I need, so trying to avoid that in all honestly.
Hope someone here can provide some guidance. Every roaster friend I got, that are running all sorts of other machines, basically came to the conclusion that my setup can't handle 100% batch sizes without extending phases or going so hot that roast defect appears.
Also, unrelated question, what is the brown/tan/mauve line in RoastPath?
I roast on a MCR 3 manual and have been charging at 80% of capacity. My roasts almost come out perfect each time. We recently tried increasing our charge capacity by 10% and noticed a considerable difference in bean behavior across all phases. We went back down to 80% for now until we are able to hone the higher charge size profile.
Looking at your example, as you noted, you are spending a lot of time in drying and speeding right through yellowing and development. Try to get get your profile to a 40/40/20 ratio. What is your bean temp setting when the PID is at 440? For example, I charge at 385 bean temp at 1.8kPA and let that ride until I hit yellowing, then I step the gas down three times before first crack. I leave the gas as is until one minute after first crack then start walking it down again at 12% DTR until reaching 0 at roughly 20%. I switched to BT a long time ago after noticing so much variation from batch to batch when going off the PID.
What are your fan speeds and drum rotation? I'm usually between 35-38 hz fan speed throughout the roast, and at 65 rotations a minute. Also, is your bean temperature the same as the room temperature you’re roast in? If you store your beans in a different room, I usually place the batches in the roastery at least 24 hours before roasting. Maybe that is much but at this point it's superstition for us :-)! One last rule we go by, the gas always decreases and never increases.
Here is an example roast: https://portal.roastpath.com/publicroasts/index/5387850413322300425
How do the roasts cup? Any under development, baked flavor?
Hope this helps and happy roasting!
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