First discovered in Ethiopia around 850A.D. the small red fruit that is the coffee berry must go through many stages to become the tasty brown bean that we all know as coffee. Most gourmet coffee is first wet processed to remove the outer skin, pulp and the inner parchment skin. The inner seed, or bean, is then dried and becomes the green coffee that is shipped and stored around the world. Green coffee is a like the dry pinto bean – it can be stored for a long time yet still become a fresh and aromatic food when it is roasted or cooked.
To make the coffee bean ready for brewing coffee the green beans must be roasted. Without roasting, a beverage made from the green coffee bean would be bitter and undrinkable. For centuries the simple act of roasting coffee was a common home task but in the early 1800’s commercial roasting of the coffee bean was introduced with the drum roaster in which the beans were roasted in an enclosed cylinder drum heated from below. Coffee beans were rotated in mass at high temperatures that would sometimes scorch and tar the coffee as the hot beans touched each other and the sides of the cylinder. Also, as the beans roast they shed a thin skin called chaff that would catch fire in the drum. This process while greatly increasing the availability of coffee beans around the world left the beans with the slightly bitter, smoky or burnt taste that has long been associated with coffee.
Then in the mid 1970’s a dramatic and radical change occurred when an alternative to the drum coffee roaster was developed by Michael Sivetz. It involved using hot air instead of a hot surface thus air roasting the coffee beans while they were levitated on a cushion of heated air. While many drum roasters began in the late 1800’s to introduce hot air into the roasting chamber, the Sivetz system used only hot air to greatly increase that rate of heat transfer to the beans creating a cleaner, more aromatic roast free of bitter tasting tars. The beans are kept in motion throughout the roasting process not touching each other, in turn not burning, eliminating the bitter taste of coffee while enhancing its rich taste. As the beans shed their skin, the hot air blows the chaff into a separate chamber eliminating any bitter aftertaste. If you are a true coffee lover then you owe it to yourself to taste the difference that air roasted coffee can bring to your brew.
With the growing popularity of gourmet coffee and an increased awareness of the superiority of air roasted coffee, there is a revival of the traditions of roasting coffee at home. You can find instructions on using a popcorn popper for air roasting coffee at home on any number of sites on the internet. Also YouTube has several excellent demonstrations of air roasting coffee at home. If you have never tasted bitter-free coffee from air roasting, you are in for a treat.