GOLDEN GATE ROASTING CLUB

The Ultimate Small Batch Coffee

April 27, 2018

In a world of ‘third wave coffee,’ where every stage of coffee production has been elevated, refined, and sharpened to deliver that transcendent cup, the emphasis has been moved from mass produced beans to carefully selected connoisseurship. "Small batch coffee" evokes a sense of quality, as it implies a care and intimacy in the selecting, roasting, and brewing processes. The culinarization and miniaturization of coffee processes work to highlight the subtle flavors that emerge from different regions, washing and roasting processes, varietals, and brew techniques. I recently had the opportunity to take the roasting process to its miniaturized and intimate extreme: roasting on a camp stove, in the heart of Golden Gate Park.  

It is hard to imagine more care and intimacy in a roasting process than the use of a campfire stove. And yet the process is surprisingly straightforward. Our setup consists of the following:

-       6 Quart Hand Cranked Whirely-Pop Popper  

-       Two analog thermometers

-       8 Oz MSR Isopro Fuel Canister

-       Backpacking Canister Rocket Camp Stove Arms

-       Lighter

-       Pasta Strainer

-       Whisk

-       Pen and Notebook 

-       Half-Pound of Green Coffee Beans (We roasted 4 half-pound batches: A washed Guatemalan, a washed Kenya, a washed Brazil, and a wet-hulled Sumatra)

All coffee roasting makes use of a graph called the Roast Profile, which tracks the temperature over time. The roast profile below shows two temperatures: 1. The air inside the oven, and 2. The beans themselves (or in our case the steel at the bottom of the popper). Different types of beans require subtle temperature differences, but all beans follow the same trajectory shown in Fig. 1.

Notice how the temperature of both the air and the steel drop off once the beans are placed into the popper. The point where the system reaches the lowest temperature (and highest temperature differential between air and bean), is called the turning point. The time between drop and the turning point is usually 90 to 180 seconds. Different varietals require different roast times, but the total cook time can be anywhere from 9-14 minutes.

For the 7-10 minutes after the turning point, notice how the temperature increase gradually levels off. It will be important to keep the heat level under control, so the stove does not flash cook the beans. If the beans cook too fast, the outer shell will have the familiar characteristics, while the inside will be green and undercooked.

Third wave coffee roasters tend toward a lighter roast, generally a total cook time in the range of 8-10 minutes. A lighter roast preserves the beans more acidic notes, which can be lost with longer cook times. This shorter cook time, resulting in a City to City+ roast doneness, emphasizes the delicate flavors highlighted in different varietals. 

As it is difficult to measure the exact temperature of the beans, we will track the temperature of the air as a measure of doneness. It is important to notice in Fig. 1 how gradual the air temperature increase is: we will want to achieve an average temperature increase of the air of about 4-5˚F every 30 seconds.

Once the popper is sitting atop the camp stove, and the heat is on, make sure that one thermometer is touching the bottom steel of the popper. Ensure the other thermometer is reading the air temperature inside the popper. After a few minutes of warming, the air temperature will reach 175˚F, with the steel reading closer to 300˚F. Once the air temperature is around 200˚F, and the steel is at 350˚F, drop your half pound of beans into the popper. Make sure the beans are evenly dispersed around the bottom. Remove the thermometer measuring the steel/bean temperature, we will be measuring the heat increase of the air the rest of the way.

Turning the crank at a constant and steady rate to slowly and evenly agitate the beans, begin taking temperature measurements of the air every 30 seconds.

Adjust the heat as necessary to maintain a 4-5˚F increase every 30 seconds. If the heat is too low, you run the risk that the beans will “stall” (stay at a constant temperature over several minutes).

If the heat is too high, you will cook the beans too fast, resulting in a charred, roasty, "baked" flavor that will overpower the more delicate flavors of your coffee.

As your beans cook, around the 4-5 minute mark you will notice them turning yellow and giving off a slight vapor accompanied by a fresh grassy smell. Make note of when the beans begin to yellow.

Keeping a continuous crank while taking temperature notes, listen for the first crack of the beans around 5-7 minutes after the drop. The sound is quite distinct, it will sound like a popcorn kernel bursting. If your beans stall, you might not hear first crack. Not enough pressure built up in the bean as it cooked too slowly. This will also give the bean a more monotone flavor profile. 

After first crack, the beans should be turning a nice brown color. First crack indicates that the beans have expanded sufficiently to begin their ‘development phase’. The development phase is the most important phase of the roast, as it develops the subtle and particular flavors that make each coffee unique and delicious.

ADVANCED NOTE: First crack will release a lot of kinetic energy (heat) into our small, sensitive system. This can create an air temperature bump. The experienced roaster will be able to anticipate first crack, and turn down the heat about 30 seconds before, to maintain a smooth heat profile as seen in Fig. 1. About 5 seconds after first crack, slowly return the heat to the previous level to maintain the 4-5˚F increase every 30 seconds.

Notice again in Fig. 1 how gradual the heat increase of the air is between first crack and completion. In the final minutes of the roast, it is important to make sure the heat increase is slowed to 3-4 degrees every 30 seconds. This prevents the air temperature from ‘running away’, or increasing too quickly beyond the end air temperature of 300˚F.

Once the air temperature has reached 300˚F, take the beans off the heat and pour them into a pasta strainer, agitating the beans with a whisk until they are cool to the touch.

Congratulations! You have roasted your very own batch of coffee! The beans will continue to ‘cook’ and off-gas for another 2-4 days, depending on the variety. Traditionally one would “cup the coffee” the day after the roast to determine its quality, and to look for any defects. For the best flavor of your freshly roasted coffee, let the beans rest for about 4-7 days.

ADVANCED NOTE: Brought your food vacuum sealer out on the trail? Try vacuum sealing your freshly cooked beans! This will shorten the off-gassing process from 2-4 days to 1-2 hours! Your brewed cup will have a very bright acidity, but it will be quite exceptional!   

Roasting coffee on a camp stove is a wonderfully thrilling experience, one that marries rugged individualism with artisanal intimacy. Just make sure you have last week’s batch, (or your vacuum sealer), so you can brew a fresh cup right there and then.

Happy Roasting!