By Rachel Beebe
In 2019 I went to the Specialty Coffee Association’s Roaster’s Camp--an industry event with workshops and lectures--in Annecy, France. One of the challenges set by the organisers that year was roasting a batch of Pacamara variety coffee. The Pacamara variety presents a challenge because the beans it produces are really big—much bigger than most other varieties of coffee beans.
Roasting a big coffee bean is a bit like the difference between roasting a chicken and roasting a turkey. Anyone who has attempted to cook a Christmas turkey that was done in the middle without also being dry and overcooked knows how hard it is to balance temperature and time when you’re dealing with a larger-than-normal mass. Unfortunately, the turkey analogy only occurred to me after ruining a perfectly good batch of coffee.
Roasters are taught to drop the beans into a hot roaster and, within a minute or two, turn up the gas to the highest setting. From there, generally, you only turn the gas down, never up. The usual logic with high grown, dense Arabica beans is that you need a lot of energy to permeate the dense cell structure, boil off the water (which is 10% of its mass in the green stage) and kickstart the chemical reactions that need to happen to develop good flavours during the roast. If you don’t get enough energy into the beans at the beginning you risk what’s known as “baking” the coffee, leading to bready, flat flavours. So, following that line of reasoning, larger beans need more energy, right?
I dutifully started with a very hot charge temperature and turned up the gas to maximum to be sure that the heat would permeate to the centre of the bean and cook it effectively. What I ended up with was an overcooked turkey.
Coffee bean sizes
Here’s another poultry analogy: coffee beans are a bit like eggs. The same plant can produce large ones and small ones. Sometimes you even get a double yolk. Just kidding. The point is, within a harvest, within a variety, even within the cherries picked from one plant, there’s some variation in size. An important step in processing is separating the different sizes using industry standard screens. To sort them, workers shake the beans through a set of metal screens with progressively smaller holes. Everyone uses the same screens, but different countries have different names for the sizes. In Colombia bigger beans (screen size 17 and 18) are called “supremo.” That same size is called “superior” in Central American countries, and “AA” in some African countries.
You might have noticed that the lexicon hints that bigger beans are better, but in practice this is not strictly the case. Traditionally it was thought that bigger beans had more complexity and sweetness because they’d matured more slowly and had more time to soak up all the good flavour stuff from the mama plant. But experienced cuppers (professional coffee tasters) often debunk this as myth. It can be confusing for a consumer who is deciding what coffee to buy. Who would buy a Kenya AB over an AA? But, on the cupping table, smaller beans often do taste sweeter and more complex. This was the case with the Malawi coffee we’re roasting soon.
The Pacamara Varietal
But let’s get back to Pacamara. Unlike other varieties of coffee, the beans from a Pacamara coffee plant are all big. And this variety also has a distinctively complex, sometimes exceptionally good, flavour profile.
Pacamara coffee plants can produce some of the most complex, delicious brews you’ll find anywhere. When we were cupping the lot grown by Alex Joaquin Flores that we’re roasting now, three different cuppers around the table identified tasting notes from four different sections of the coffee flavour wheel. There’s ripe stone fruit, sweet citrus, honey-like florals and a dark chocolate note in the finish.
In the case of Pacamara the amazing flavours and the large size might actually be connected because it gets them both from one of its parent varieties, Maragogipe (super fun to say: “mara-go-hee-pay”). In 1958 coffee scientists at the Salvadoran Institute for Coffee Research created Pacamara by crossing a Pacas, which is a small, hearty mutation of the Bourbon variety, with a Maragigipe, which is a giant mutation of the Typica variety. Bourbon and Typica are the two main strains of the Arabica species, so crossing them makes sense from a biodiversity standpoint. This particular cross was intended to take the exceptional cup quality of the Maragogipe and combine it with the toughness and higher yields of Pacas. It took about 30 years to isolate and stabilise the manmade Pacamara cultivar but it was eventually released to producers in the late 1980s.
I haven’t had the pleasure of tasting many Pacamara lots, but according to the folks at Ozone, who have a nice long blog post about the variety, they can be a mixed bag. “Of course there are bad examples, and in fact when they are bad, they are very bad. Vegetal, mushroomy, dirty, cardboard Pacamaras are very very very common,” they report. They’ve been roasting the variety since sourcing it directly from the Mierisch family’s Cup of Excellence winning farm Los Limoncillo in Nicaragua over a decade ago, so they know what they’re talking about.
How we roasted this coffee
So, how are we neither burning nor baking Alex Flores’s beautiful coffee? Ludwika discovered the secret weapon: airflow. To explain we need to do a little coffee roasting 101. In a roaster there’s three kinds of heat: conductive (the metal of the drum is made hot by the burner and that heat is transferred to the beans when they touch the drum); radiant (the walls of the drum are hot so they heat the environment of the roaster up and some of that heat gets transferred to the beans); and convective (hot air is pulled through the roaster, creating negative pressure, and transferring even more of the heat from the environment to the beans). You can’t roast coffee well without convective heat. It’s the most efficient type of heat transfer. If you try to roast without a fan providing convection you’ll end up with coffee that’s scorched on the outside and green in the middle. Or your roast will take so long that you’ll bake it, and it’ll probably also be a little burned.
To create the hottest possible environment in the roaster at the beginning we raised our charge temperature by about 7 degrees C. But, importantly, in order to not rely too much on the gas and conductive heat transfer (which would scorch the beans), we increased the airflow from the beginning of the roast. This works differently in different roasting systems, and I can’t claim to fully understand the thermodynamics of coffee roasting, which is more complicated than it might appear at first glance, but in this case, it worked! We were able to generate enough heat to get the roast going and hit the temperatures needed within the right time frame to roast the coffee well.
Above is a graph with time on the x axis and temperature on the y axis. The yellow line is a washed Mexican coffee, and the blue line is the Pacamara. The curve shows that the Pacamara roast starts out a lot hotter, but takes longer to roast and ends at a lower temperature. Because the ratio of heat transfer in the first part of the roast was more convective and less conductive, we didn’t scorch the beans, and because we eased off the gas relatively quickly over the course of the roast, we were able to control the temperature toward the end, when there’s a high risk of roasting out too much of the organic acids (which is where all the lovely fruity flavours come from) and over caramelising the sugars, burning them and turning them from sweet to bitter.
In my experience, roasting is a little bit science, a little bit craft and a little bit luck. There’s things you can control, like gas setting and airflow, and there’s things you can’t control, like roaster setup, environment and the experience you bring to the table. Ludwika and I are lucky to have a reliable roaster that we know really well and a combined 15 years of roasting experience. And still, we’re learning and excited to taste what’s possible.
Our Pacamara from Alex Joaquin Flores is available online and at our roastery in North Berwick now.
Resources:
https://perfectdailygrind.com/2015/11/interview-whats-so-special-about-pacamara/
https://ozonecoffee.co.uk/blogs/varietals/coffee-varietal-pacamara?