What happens when you roast a coffee to the same roast level but at different rates of development?Read More
Nov. 16, 2017
First off, I was really surprised by the amount of emails and comments my initial Behmor roast profile blog post generated, and truly enjoyed reading people's responses. There were a lot of personal insights and experiences shared with me that got me thinking about how different roast approaches might benefit one coffee over another. Much of the discussion was around the challenges that come with trying to mimic a roast profile considering the unique variables affecting roast outcome, whether it's dealing with hot and cold ambient temperature, high-use machines with dirty sensors, voltage output from one home to the next, etc. In a word, those looking to replicate the roasts I'm sharing are asking for more specifics.
This time around I wanted to try roasting a coffee that I thought would show well when roasted longer. I didn't want to do another "light and bright" roast approach, and so I looked for a coffee with solid core bittersweetness when roasted darker. I wound up settling on Honduras Corquin La Lesquiñada, partly because of how well the dark roasts from our sample roasting machine cup-tested, and also because I figured the combination of moderate moisture content (11.8%) and large bean size would hold up well to a longer roast development time.
Before I go through my roast profile, I'll give a quick rundown of the variables in my roasting room, and tell you a little about the two Behmors I use, in order to give you an idea of the conditions under which I roast. My roasting room is in a Seattle basement, which since it has good ventilation is probably not quite as damp as most! But it is getting colder, and on this particular roast day the temperature in my room with the window and back door left ajar for smoke ventilation got down to 62F. Not too cold really, and I don't think it slowed my machines. Come December, I doubt I'll be able to say the same!
Most any multi-meter will do for checking voltage
The wiring in my house is fairly new, and I measured the voltage output from my wall outlet at a solid 121 volts. Older wiring, or use of extension cords, can choke up voltage output, and in turn, make it impossible to get the maximum performance from your roaster. Finally, the Behmors I'm using only have about 12 roasts each, and I wipe down the inside with mineral spirits every few roasts, so I know the sensors are clean. Dirty sensors will have a prohibitive effect on their ability to read temperature, and since the Behmor relies on these readings for automation, you might find lag times on the auto-heat adjustments when using pre-programmed roast profiles.
It's also worth noting that our own experience has shown that not all Behmors are created equally. It's not the build per se, but we have noticed some variance in roast curve between different machines. I don't think it's that big of a deal really, and like any roaster, you get used to using your machine, making the necessary adjustments to produce roasts you like. After all, you're mostly roasting for your own taste, and not to try to follow someone else's roasting instructions. But when trying to follow a roast outline like the one below, don't expect precise replication of roast progression, the extent to which is determined by the variables outlined above, and the machine itself.
Weighing the coffee before and after roasting is a good way of measuring roast development
For the sake of comparison, I laid out plans for two different roasts, the first a City+ roast with a slightly extended finish in the hopes of toning down acidity for a dual-use brew/espresso roast. For my second roast batch, I wanted to follow a similar roast trajectory the first 2/3, then extend the roast time from just before 1st crack (1C) until the end, ultimately getting to Full City roast level. I'm roasting on two different Behmors, so part of the reason to follow the same roast pattern for the first 2/3 on both machines was to test the roast consistency and predictability. All in all, I was able to replicate the profile fairly closely on both machines, however, as the notes show below, Roaster A seems to run a little hotter than Roaster B.
Hopefully the outline below is easy to read. A few parameters are outlined in the top three rows, and the "Approach" columns contain my roast plan, a more general set of notes that I use as a directive when trying to acheive my desired roast profile. The first three columns for each roast show the actual minute-to-minute activity (the left number is ascending minutes / right number descending minutes on Behmor's display), and any heat adjustments I made along the way.
[click the graph to enlarge]
A few notes on the roasts:
You'll see that I make no heat adjustments until around 7 minutes in, which is when my roasters near the dreaded overtemp error shutting down the machine (325-330F). This is also around the time that the fan begins exhausing hot air from the roasting chamber, which some folks mentioned is enough to keep their Behmors from erroring out at all in with the high heat setting (P5) in manual mode. This is not the case with my Behmors. And while the exhaust does turn on at 7:30 in the 1lb setting, the temperature continues to rise, and eventually overheat when loaded with 200 grams of coffee, and so I have to decrease my power output to avoid this. (I will play around with batch size in the future to see if this can be avoided without having to dip the power).
For the roast in Roaster B, I turned the heat back up to P5 after the temperature dipped to 307F, and it continued to drop for almost a full 30 seconds, bottoming out at 293. I intentionally did not increase heat to P5 in Roaster A in order to draw out the overall roast time, and ease into First Crack (1C). This definitely put the breaks on roast development, and you'll see there is 1:35 second difference between the start of 1C.
It's also worth noting that Roaster A seems to run hotter than Roaster B, though I'm not sure if it's due to machine variance or operator error. You can see that my start temp in A is 13F cooler than B at the end of minute 1, advances 9F faster than B by minute 2, passing it by minute 4. This could be machine related, or perhaps it just took me longer to load the coffee after pre-heating. The pre-heat/drum-loading stage is perhaps the least precise part of the roast, the amount of heat loss directly tied to how long you leave the door open. The drum mounts can be a little tricky to seat a drum in when the machine is cool, making loading in a hot machine all the more precarious. Basically, sometimes it takes a little longer to load a hot machine and therefore, start temps will understandably vary.
A mere 2% difference in roast development is night and day in the cup (roast B (light) on left and A (dark) at right)
Judging the final roasts visually, the more developed level of the Roaster A batch is apparent, though the degree to which is perhaps better expressed in flavor. The exterior color of roasted coffee is not always the best indicator of roast level, as internal roast degree is not something you can see, and will vary depending on how long it takes you to reach your desired roast level.
One way to illustrate this is to consider cooking two steaks to internal temperature of 135F, but doubling the time it takes to get there in one of them. You would expect the longer cooking time to bring the internal and external temperatures up at a much more uniform rate, most likely compromising the non-uniform layers of "doneness" that you rightly expect for medium rare (I apologize in advance for the coffee/meat comparison!). The same thing happens with coffee, and if your roast curve is too slow, you risk baking the coffee and compromising some of the complexity that comes with a coffee beans exterior and interior cooking at different rate.
I say all of this in order to better explain another visual check that we like to use when judging roast degree, which is putting the ground coffee from different roast levels next to each other. Grinding the coffee gives a much more uniform impression of roast level, which in this case more accurately illustrates their differences.
It's hard to see the beans in this photo, but they don't show near as much color variance as the ground coffee (roast B (light) at left and A (dark) at right)
Roaster A: There's little more than 1.5% difference in weight loss between this coffee roast and the other, but the profiles contrast starkly. Smoky BBQ smells were emitted in the fragrance and aroma, and bittersweet indications of dark cacao nibs are pushed to the front throught the cup profile. This roast will certainly appeal to folks who enjoy the bittersweetness that comes with roast tone, and the coffee offers up a bit more as it cools. Subtle dry fruited notes provide mere accents, and the pungent burned sugar flavors fill out the base, giving way to lingering powdery cocoa flavors in the finish.
This roast was intended for espresso, which it functions well as, though the smokiness was a little overbearing for me. One final thought on this profile is that I tasted it at three different rest intervals - straight out of the roaster, with 24 hours, and also 48 hours rest - and the smokiness is much more dominant without rest. 48 hours is where those roast tones find harmony with layered sugary sweetness, leaving a bit more room for some of the nut and dried fruit accents to come through as well.
Roaster B: This is definitely the lighter of the two roasts, though still displaying characteristics of a well developed coffee. What I mean by that is this roast showcased rounded sweetness, and while nut flavors came through too, they are a reflection of the coffee itself, and not the grainy/green nut notes that come with underdeveloped roasting.
Like the darker roast, a smokiness was most present when tasting the coffee just out of the roaster, but then much more balanced out with two days rest. A raisin-like sweetness builds in the brewed coffee, matched by dry fruit aromatics, that along with sugar browning notes jogs memories of coffee cake made with raisins. Acidity is most noticeable when the cup temperature dips a bit, so sit with it for at least 10 minutes. That's what I did, and I was rewarded with plum-like brightness, as well as a candied orange peel note, both bringing structure to the cup.
There's a surprising chocolate heft at this roast level too, layers of dark chocolate and carob, that pair well with the emerging dried fruit flavors. I have to say, this roast made for fantastic espresso after a full 7 days rest. The raw sugar sweetness is intense as is creamy mouthfeel, and fruited caramel and bittersweet chocolate torte flavors dominate the cup.