Using an air popper is pretty straightfoward; The hot air flows through the beans, agitating and roasting them as it does so. The tricks are the size of the batch, and timing. You cannot directly control the amount of heat the popper provides, save some tricks with voltage and electric cable lengths, unless you modify the popper’s electrical systems. So for the most part, it comes down to timing, and batch size.
I tend to favor the dark roasts, with the darker fruits, cocoa, and chocolate notes. I like earthy flavors as well, provided they are a clean taste, not too ashy. I don’t like the brighter fruit, acidic flavors, but I am learning to identify and possibly appreciate them a little more. I chose 3 different beans to start my roasting experience off with: Sumatra Pak Lintong Joner, Yemen Mokha Harasi, and Guatemala Puerta Verde Bourbon.
For the first batch of beans I chose the Sumatra, and based on some initial testing, determined that 3 ounces of green beans was about the right batch size. This was based on the manufacturer’s recommended weight for popcorn kernels, as well as several tests observing bean agitation in the popper.
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The main requirement of the air popper is the vent design. The recommended design is the side vent model, which creates a vortex air flow, agitating the beans in a circular manner. There are models with a mesh grate at the bottom that agitates the beans too much, often ejecting beans if the batch size is too small. It can also burn the beans if they are not properly agitated, or sit on the grate too long.
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The beans can be loaded directly into the air popper, just like popcorn kernels. However, care must be taken, as there are still some fire hazards during this process. As the beans heat up they will expand, which will cause them to shed their outer skin (the chaff), which can catch fire, if exposed to high heat. Most of the chaff will be blown out of the air popper during the roast, so ensure you have a bowl to collect it during the roasting process, or you can let it fly everywhere.
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The roast goes pretty quick, so ensure you stay close to the popper throughout the process. Once you start the popper and ensure that the beans are properly agitating (they should be moving, otherwise they will just burn), it should take around 3-4 minutes for first crack, and 6-7 minutes for second crack. There are multiple indicators of roast progression, including color, sound (first/second crack are audible), as well as the aromas of the smoke. These indicators will become more apparent with experience.
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Once the beans reach first crack, they are drinkable, so it comes down to what flavors you are looking for in the beans. The flavors after first crack are more acidic, brighter fruit flavors. As the roast continues, the flavors will get darker. At second crack, the roast is getting into an espresso roast, and too much further will result in an undrinkable cup of coffee. The closer you get to, or past, second crack, the flavors are less expressive of the bean, and the roast process starts influencing the flavors.
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Once the desired roast level is achieved, it is essential to cool the beans as quickly as possible, otherwise they will “coast” or continue to roast, if not cooled quickly. A colander will help with air flow, and the beans should be agitated to ensure they cool quickly. The beans will continue to release CO2 for at least 12-24 hours, so they should not be stored in an airtight container. They can be consumed immediately, however flavors will continue to develop as they de-gas, so I usually wait at least 24 hours before grinding them to make the first cup.
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A close inspection of the beans can be very informative. Some of the beans are definitely darker, indicative of an uneven roast, which may be caused by a lack of agitation, or the lack of control over the amount of heat applied. As an introductory step into the world of home roasting this was definitely considered a good start. It provided a Full City+ Roast, and the coffee was delicious!
I did several roasts using the air popper, and implemented a timer which helped to identify when the beans should be entering first/second crack, which helped to distinguish between Full City and Full City+ roasts. With the model of popper I was using, and knowing the wattage, it was possible to calculate down to 30 second intervals for roasting stages, which definitely helped control the overall timing of the roasts. The air popper roast had limited options for heat and controlling the roasts, so I have moved away from this method, to an even more manual method, but one where I can control just about every aspect of the roast. Of course, that will be a topic for another post.