This is the second of a series of two articles about roasting Ethiopian coffee. Previously, experienced roasters Dudley Powell and Lukas Komurka explained how they navigate the huge flavour potential of this origin and why profiling heirlooms can be challenging (see part 1 here).
Here, they’ll share roast profiles for Natural and Washed Ethiopian coffees, compare roasting in different machines, and control the heat as they approach the first crack in highly charged roasts.
They will also talk about how to make sure you have a uniform roast when dealing with green coffee beans of different screen sizes.
Different roasteries approach profiling in a variety of ways and there is no ultimate solution for a coffee lot. Sharing the experience of these two roasters is simply a way to broaden one’s set of tools to achieve a great cup!
Using a Standard Roast as a Starting Point
Once you have chosen your coffee and explored the potential in the cup by sample roasting in a few different ways, it’s time to go to the big machine.
At this point, Dudley reviews the roast curves of previous Ethiopian coffees he roasted that had a similar density and flavour profile. He uses them as a starting point, changing variables to bring out the aromas he picked when roasting the sample.
If you never roasted Ethiopian coffee before, you can use Dudley’s roast as your starting point. He uses a 12kg batch size on a 35kg machine.
Keep in mind that production roast curves won’t translate directly to your machine. But the logic behind a roast profile can be tweaked to suit your own settings.
Dudley’s Roast Profile for Ethiopia Fully Washed Sidamo
With a Washed Ethiopian, he’ll bring out the juiciness of the coffee, boosting body and sweetness by prolonging the development time.
Dudley’s Roast Profile for Ethiopia Anaerobic Natural Guji
With Natural Ethiopian coffees, Dudley chooses a faster, hotter roast with a shorter development time, looking to enhance floral notes and acidity.
Working Through Your Variables
At Horsham Roaster, Dudley uses the same charge temperature for all single-origin coffees. What varies are the total roast time and the gas input throughout the roast (see roast curve above).
Having something fixed helps him maintain consistency and systematically change the other variables to achieve the flavours he’s looking to enhance based on the sample roast.
“For the Natural Ethiopian I mentioned, I wanted to get to the first crack quicker, so I went to 100% [gas] for the first injection of heat and then reduced the heat in a controlled and measured way, allowing for just the right amount of development.”
Air Roaster vs Drum Roaster
Dudley uses a Loring S35 Kestrel. According to him, the air roasting machine helps him roast faster than he would in a traditional drum roaster. He says it’s easier to have a gentle heat reduction throughout the roast even when the charge temperature is high.
Horsham’s Head Roaster believes there is a higher risk of scorching if you use a drum roaster. Scorching is a roast defect that happens when the charge temperature is too high and the drum speed isn’t fast enough. As a result, the bean’s exterior ends up with burnt patches.
A really hot drum can derail the entire roast and shorten the Maillard phase. Having a good between-batch protocol will reduce that risk as the days go on and the heat builds up.
Managing Heat as You Approach the First Crack
“After the first crack, the temperature of Naturals in particular can rise exponentially, so there I’d advise watching the rate of rise up to the first crack really carefully. There’s also a risk of underdevelopment, although some people actually enjoy those slightly more vegetal, peanutty flavours too.”
Finding the sweet spot here is a “balancing act”, as Dudley puts it, and there is no one-size-fits-all approach. It’s important to know the machine and how different coffees react.
As a general rule, he advises approaching the first crack with enough energy to avoid a crash, which can lead to underdevelopment and a lack of sweetness.
On the other hand, “too much energy and you will risk the end temperature running away from you and therefore your outer colour will be too dark before you have the desired amount of development time”.
How to Roast Beans of Different Sizes: the Middle Soak
Ethiopian beans tend to be of small screen size, around 14 to 15. But the screen size is less consistent than in coffees from other origins - even when you buy a Grade 1, as the country’s grading system is based on defects.
“Over the years, I have observed that often, due to the variation in sizes, my Ethiopian beans were prone to roasting at different rates,” explains Lukas. “To mitigate that, I started experimenting with what I call ‘the middle soak’.”
Lukas’ method is similar to Scott Rao’s “the soak”, but he uses it at a different stage. In the soak, the coffee is dropped into the roaster with very little gas or no gas at all. The beans “soak up” the heat built up in the drum (the gas will be on until the last second) for one or two minutes.
Lukas has tried the middle soak on both drum and air roasters. This is how he approaches it:
- He starts by turning up the gas in the drying phase of the roast, for about one minute.
- At around the turning point, he switches the burner off, letting the beans soak up the initial heat for 60 to 90 seconds. Only then he kicks on the gas again, usually at 80%-100%.
- Right before the gas is back up, “you can see the beans taking on more even colours, rather than a mix of green and yellow,” he says.
- Once the heat builds up, not a lot changes. You can “roast to your final time and temperature, and you end up with a much more even roast.
Though the rest of the roast is pretty similar to a classic profile, “the middle soak method prolongs the Maillard phase and the coffee usually turns yellow earlier”.
Lukas also says that the temperature needs to be stabilised before you approach the first crack stage, as the sharp gas uptick mid-way can build momentum too fast.
Lukas Komurka Middle Soak: Guji Natural for Single-Origin Espresso
Filter Roast vs Espresso Roast
As the middle soak prolongs the roast, resulting in more body, Lukas recommends it when roasting Natural coffees for espresso. For Fully Washed coffees to be enjoyed as a batch brew or pour-over, he uses a more classic roasting method.
“I think Ethiopian coffee actually works really well as an espresso that’s served with milk,” he says. “I like my espresso to be full-bodied with a nice sweetness, and Ethiopian coffees can be perfect for that style of drink.”
Some people in the industry believe that you would only “waste” lesser quality Ethiopian coffee on milk-based beverages. This is not how Lukas and Dudley (and Algrano, for that matter) feel.
A great Ethiopian can transform a flat white or latte. It can even help introduce new customers to specialty.
Lukas Komurka Classic Roast - Guji Natural Lukas recommends calculating the weight loss of the roasted coffee after a batch. “I aim for a weight loss between 12.5% to 13.5% for filter roast and 13% to 14,5% for espresso.”
The percentage varies depending on the water content of the beans, but there is another positive in tracking it. “The weight loss gives me good feedback about my consistency.”
The roaster also changes the batch size. Currently roasting on a Loring S15 Falcon, he roasts 8kg for filter and 12kg for espresso. He has applied the same logic on a Giesen W6, roasting with no more than 4kg for filter and up to 4.5kg for espresso.
Back at Horsham, Dudley also works with Ethiopians for milky beverages. “I love the way that the brightness of Ethiopian coffee cuts through the creaminess of the milk,” he says. A Natural coffee would be Dudley’s first choice for espresso, ideally with a strong floral or berry profile as well as milk chocolate notes.
To roast a Natural, “I would extend the development time by 30 seconds or so to reduce the acidity. And if it were a Washed coffee, I would look at a slightly higher end temperature. But in general, the way I approach high-quality single-origin espresso and filter roasts are very similar.”
Not Always Easy to Roast. Always Vibrant.
Ethiopian coffee may need more trial and error to achieve the best results, but the payoff is in a unique cup in the end.
“I’m always excited to work with Ethiopian coffees because you don’t know exactly what you’re going to get,” concludes Lukas. “It’s always slightly different, and that’s the great thing about Ethiopian coffee. It makes things much more interesting.”
Dudley’s main advice for roasters working with Ethiopian coffee for the first time? Keep things simple. “Start from a previous roasting curve that’s worked for you and take it from there. Chances are that it’s going to taste great” he says. “Think about development time, colour, and end temperature. Don’t overcomplicate things.”
Despite all the variables, roasting Ethiopian coffee can be easy. “They can be so vibrant, meaning a less-than-ideal roast will still give you an interesting coffee,” Dudley says
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