Roast #6: Dialing in a roast
You used to call me on my cell phone... Late night when you need my Ethiopian Guji 20-day anaerobic coffee roasts.
How you roast will result in different flavor profiles for your beans.
Of course, a "dark roast" will be different than a "light roast," but the complexities and differences don't just stop there.
Other factors that you have to consider that'll affect your roast include:
How is heat handled throughout the roast and how does your Rate over Rise (RoR) curve look
How long does the roast stay within each phase (drying phase, browning phase, development phase)
How long certain chemical reactions are allowed to happen for
But to determine what strategy works best for each bean, you must go through different roasting strategies to refine and pinpoint what works best for that type of bean.
My process for the Ethiopian Guji
I think this bean is an interesting one to diagnose because of how much more difficult I found it to have been compared with the others.
The Ethiopian Guji was my first ever heavily fermented bean. I didn't have a strong understanding of what I was getting myself into with these beans. I thought the extended fermentation would bring a unique characteristic to the bean, which it did, but it also brought additional complexity.
Attempt #1:
Roasting targets:
Fast roast (<8 minutes) to try and highlight acidity
12%-15% development time ratio
The result of this roast wasn't great. After cupping, we found the brew to be very umami-like with some very savory qualities.
But this roast didn’t entirely go to waste. I was able to get my bearings with this coffee by figuring out some basics about this coffee.
Insights:
It was hard to determine when "yellowing" started. I think given that it was a super fermented natural, there was already a lot of dark discoloration in the beans. So they weren’t that green to start with, so figuring out the point when the beans started to yellow was confusing.
We can expect hints of first crack at around 190C, with us hitting a rolling first crack at around 200C.
Attempt #2:
Roasting targets:
Longer roast (> 8 minutes)
12%-15% development time ratio
Use a drum strategy that would push more heat into the beans.
Insights:
I still got some hints of umami flavors
But I also started to taste hints of acidity and bursts of fruit.
Other than still tasting some hints of umami, this roast didn't provide much insight. I realized that I still had some roasting discovery to do.
Attempt #3:
Roasting targets:
Skip on DTR, and drop right at rolling first crack
Try for a shorter roast to highlight acidity
Insights:
I still got some hints of umami flavors
Shorter development time didn’t seem to have an effect on why the umami flavors were being exhibited.
Attempt 4:
Roasting targets:
Skip on DTR, and drop right at rolling first crack
Go softer on heat for a longer roast
Upped power to P5 instead of P7 (in roast #3) post-soak
Insights:
The umami was gone! The resulting flavor was a very upfront raspberry note.
The bean was receptive to the softer heat, as it could still decrease RoR steadily.
The sourness could be mellowed a bit.
So after four different roasts, I finally found a profile that I liked and was comfortable selling and refining.
Post-Roast Analysis:
I went back and tried to deduce what was happening in Roast #4 that made it a better roast than the prior two.
I divided each roast by when specific chemical reactions should happen. The chemical reactions I used for this naive analysis were just
Maillard Reaction (from 140C-170C): This is a non-enzymatic browning reaction caused by the interaction of simple sugars and amino acids, particularly in the presence of heat (per Ally Coffee).
Caramelization (from 170C-200C): The process of browning a sugar (per Wikipedia).
From the data gathered, we could see that what made roast #4 unique was how much longer (~25% more time) the roast spent in the caramelization reaction phase.
What was also interesting was that even with an extended maillard reaction (roast #3), the umami flavors were still pretty intense. The Maillard reaction is known to be responsible for umami flavors, so my guess is that that's what's producing the taste. The extended caramelization was what helped mellow out the umami flavors, better balancing the acidity from being umami and savory to more sour and fruity.
So in conclusion, the points I wanted to convey in this post are:
How you roast will affect the end flavors, and it doesn't take much to go from a savory profile to a fruity one.
Nailing down a profile can be tedious and hard. Sometimes it takes multiple iterations and rounds of testing to get a profile down. Other times you get it on the first try.
If you are interested in trying this coffee, I have a few bags left for purchase at my online shop!