I'm looking for a little feedback about one of my roasting profiles. I've been roasting for more than 10 years, but never really gave a second thought about what I was doing. Until recently, I just tossed about 3/4 of a cup of whatever beans (sometimes a mixture) into the roaster and followed the same profile day in and day out. I'd like to actually start thinking and learning more about what I'm doing, and how I'm affecting what's in the cup.

I have the feeling that I'm hitting first crack a little too soon. If this is the case, I *think* I need to keep my drop temperature the same, but either add heat more slowly, or introduce more air so as to slow the roast down a bit? I very well may be wrong about the whole thing though, so I'd love to hear any and all thoughts.

Here's my roaster:



It's a drum sample roaster (100g) hard-plumbed to natural gas. It's got a thermometer in the upper part of the drum, but doesn't give me bean temperatures, so I basically use it to help me determine when the machine is warmed up. For bean temperature monitoring I use an IR gun, which I point into the drum at the beans in the same location every time. Not ideal, but I don't know of a better way.

Air flow is controlled by a lever on the right side of the machine. An HVAC fan draws air from the roasting chamber.

I cool the beans to room temperature within about 45 seconds by sucking air through the bottom of the cooling tray (removable) with my big shop vac.

And here's my roast profile (typed out on Mac Pages):




This batch was a Yemen Haraaz A (tree dried). 100g. First crack was at 6 minutes 9 seconds, and dropped at 9 minutes. 2nd crack started at 9 minutes. The majority of my beverages are straight espresso and espresso/milk based drinks.

Thank you for taking the time to read this, and I appreciate any advice. I know in the end, it's all about what it's like in the cup, and more often than not I'm satisfied. However, I'm sure that I could be doing it better.

For me I may go just the start of 2nd crack but never farther..
With my roaster I like 1st around 9 minutes and will drop around 2:30 minute

I would say try doing a few roasts increasing your 1st crack time 1 minute..
If it tastes better, increase your roast another minute till they get worse..

Thanks! I neglected to add that, with this profile, the coffee has a bit of a funky taste to it. It's hard to put to words, but I liken the taste to how the coffee smells when it starts to become yellow in the roaster. Sort of like a dried hay that is wetted if that makes sense?

What I'm thinking, and remember that I've just been mucking my way around roasting all of these years, is that the outside of the coffee is being roasted but inside the bean not so much. Thus the reason I think that I need to extend the time to 1st crack.

Pre-roast bean weight was 100g. Post-roast weight was 84.2g. Not sure if this is of any significance or not, but I think it might? I'm just not sure how to make a correlation?

Try this: Start with a higher heat and leave it constant throughout the roast until first crack. Use moderate air at the start, and then increase it once your beans have turned fully yellow (which is often called, somewhat erroneously, "end of drying"). Do not increase your heat setting at this point; instead, choose a charge temperature and heat setting that will get you to the beginning of first cracks between 6 and 8 minutes after the start of your roast, if left unchanged.

Once first crack begins, steadily dial back your heat to slow down the rate of rise, but not so much that the temperature stops rising altogether. Do some experiments to figure out the timing necessary so that the decrease is smooth, without an upward "flick" as first cracks subside.

For my taste, I get best results for espresso finishing my roasts at around 20-25F beyond the start of first crack, with this "development" phase lasting about 20% of my overall roast time. This is a "city plus" roast, a bit lighter than your "full city" roast, which reached the first pops of second cracks. YMMV, both because different people enjoy different flavor profiles and because much depends on the way that bean mass temperature is measured between different roasting setups.

One final suggestion: Install a bean mass and exhaust temperature probe on your machine, and start tracking the data using roasting software (can be on a tablet or a laptop, as you prefer). The more info you get from each roast, the easier it is to learn from your successes and failures.

Start with a higher heat and leave it constant throughout the roast until first crack. Use moderate air at the start, and then increase it once your beans have turned fully yellow (which is often called, somewhat erroneously, "end of drying").

What is the reason for doing this?

One final suggestion: Install a bean mass and exhaust temperature probe on your machine

How would I install a bean mass temperature probe, and what would I use? The only direct access to the beans is through the small port that you see at the front of the machine.

What is the reason for doing this?

Scott Rao has a theory that a declining rate of rise promotes more even bean development. Starting with higher heat and progressively reducing it help you achieve this profile. Whether or not he is right about the reason, I find that this approach tastes best for most coffees I have tried it with.

The air recommendations are based on my own experiments, in which I compared the results of lots of different airflow approaches in my sample roaster on the resulting taste profile, keeping all other factors constant.

How would I install a bean mass temperature probe, and what would I use? The only direct access to the beans is through the small port that you see at the front of the machine.

I recommend a K-type probe without too much shielding, so that it responds quickly to changes in your roast. As to how to install it, I'd ask other people who use similar machines as yours. It might be as simple as drilling a hole in your faceplate, but you'll want to route it so that it doesn't interfere with the stirring vanes. I can't give much guidance there since I've never used an open-barrel roaster.

Looks like I need to purchase Rao's book!

I too have been mucking around with roasting for some time but go mostly by feel other than using a timer. Lately my best roasts for espresso draw out time as long as possible. 10-11 min. to 1C then reduced heat to lengthen time between 1C and 2C, stopping at very beginning of 2C around 14-15 minutes. I think it was when I was roasting much quicker that I remember a funky flavor like you were describing that would disapate after 4-5 days post roast.

Interesting. At what point would one consider it "baking" as opposed to "roasting"?

The funky taste comes from natural processing (tree dried, fermentation)

Extend drying time (time BT Less than 300f)

And follow Rao's advice for high charge temp and declining ROR throughout to avoid baking (where temp is steady or declining)

How do both?

Charge hot then turn off power.

When temps hit turning point, crank up power again and ride the curve to extend the dry time.

You can decrease power before first crack to avoid flick of death (bump in temp cause by shift to endothermic reaction)