The coffee bean is the seed of a sweet ripe cherry. Much like wine, it contains a wonderful combination of flavors from the variety of the fruit as well as the ground in which it is grown. Climate and altitude obviously play major roles in the complexity of the overall flavors of the fruit. As such, the seeds of the cherry, your future cup of coffee, also carry these flavors; and the real art to great roasting is preserving this character as much as possible. Over-roasting results in loss of most of these flavors, and so it is imperative to us, that even our Darker roast retains the character of our beans.
For David’s Roasting, we chose the fluid bed method for several reasons. Fundamentally, a fluid bed roaster is a lot like a hot-air popcorn popper. The hot air is forced through the chamber where the beans are contained, and allowed to circulate around each bean more consistently. As the beans roast, they become lighter, due to the loss of water and are blown around more and more. This allows them to circulate more efficiently through the chamber. The hot air moves the beans. The temperature sensor allows for a consistent monitoring of the roasting process and we can control it much more accurately. Additionally, the chaff, or outer skin of the bean, is blown off completely and kept away from the beans during the entire process.
By contrast, the drum roasting method, rolls the beans inside a metal drum. Contact with the metal drum often creates an uneven roasting process. Coffee roasted too quickly, or with too much heat may also be unevenly roasted throughout the bean. Likewise, coffee roasted too slowly or with inadequate heat will be completely void of the natural flavor oils and compounds. Much of the burned chaff stays with the beans until the cooling process, adding unwanted flavor. Additionally, drum roasters tend to need a much higher operating temperature in order to properly roast the beans, making it harder to achieve consistent results in a lighter roast profile.
Below are several pictures of the roasting stages using our fluid bed process; from their initial green stage, all the way through to the finished product. This takes approximately 18 minutes start to finish, including cooling, depending on the roast level.
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- Green beans
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- In the first few minutes the coffee actually becomes paler as it loses water and dries.
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- The beans are starting to assume a browner color, and a marbling appearance is starting to emerge. The first “toasty” smells (like toasted grains) can be detected, and less humid air coming off the coffee.
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- Just before first crack. The coffee has browned considerably, which is partly due to browning reactions from sugars.
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- First crack is done. This is considered a City Roast. The bean surface is smoother somewhat from expansion but still has darker marks in the coffee. The edges of the seed are still fairly hard. At this point the coffee starts giving off carbon dioxide.
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- Full City +, the coffee has barely entered 2nd crack. As you can see, compared to the green beans, these are much larger due to their expansion. In fact they will often be double their original size. They also flow freely though the entire chamber because they are much lighter.
