Perhaps you love coffee and would like to experiment, you may be looking to replicate the fresh coffee you tried in some cafe, or you may simply be starting to question why you spend so much to buy roasted coffee from someone else. Coffee is an industrial product like beer, and also like beer, you can create it yourself, giving up some quality control but gaining a much fresher product.
There is a lot of information on roasting your own coffee, starting with green coffee beans, none of it particularly definitive. If there was one book that touched all aspects of the process, it was Home Coffee Roasting: Romance and Revival by Kenneth Davids. Sweet Marias, a sourcer for green coffee, also has an excess of material (for free).
Generally, there are three characteristics to consider when roasting your own coffee:
- sound, and
Experience with these variables will allow you to know when your coffee is done roasting. Keeping track of your results is key to recognizing a pattern of complete roasts.
To vastly oversimplify, coffee is done roasting when it has started “popping” and then concluded and has a uniform brown to dark-brown color. There is a simple technique to hand-roasting, which involves rotating the beans so they don’t scorch, either using a Whirley Pop, as I do, or another machine, such as an air popper or home roaster.
Roasted coffee is grouped by color, which makes sense because it’s the most apparent feature for the consumer. Dark roasts tend to have more caramelized or burnt flavors, while lighter roasts tend to showcase brighter fruit flavors. Too light, however, and the coffee will look inconsistent and have a grainy, not pungent smell once roasted.
Home roasting is not particularly precise, though it is fairly simple to stop your roast somewhere between City+ and Full City+ on the color scale above.
After constant agitation and a low flame, my coffee starts to “pop” after around 4 minutes and 30 seconds. I’ve tried at lower temperatures and drawn out this phase for 6-8 minutes though have found I can repeat my results with a slightly faster roast. After usually 1 1/2 or 2 minutes more, the “first crack” is complete and there is a brief lull at 6 minutes. This is a signal that the lighter roast process is complete. Depending on your level of heat, this process may take as much as 10-12 minutes.
You may stop your coffee here and transfer to a strainer to cool if you prefer a typical East Coast roast. The diagram below shows the interaction between first and second crack:
Another minute or two, often around 8 minutes for me, the “second crack” begins. Following the roast process to this point begins to create a Vienna or French roast. At this level, burnt flavors start to overwhelm the coffee pungency. You’ll know you’ve reached this level by the dark brown color and spots of oil that appear on the coffee beans. After the second crack, the beans also appear both larger and lighter than previously. Vienna will be sligthly oily, while French roast beans will be larger, lighter, very dark, and very oily. Going past French roast risks a fire.
While I am able to create consistent results controlling my stove heat, time, and color, I have also inserted a metal candy thermometer into the lid of my Whirley Pop. I heat the empty container to 400 degrees before dumping in 1/3 lb of green beans. After a few minutes the air temperature in the roaster tends to bottom out slightly over 200 degrees before it starts to rise again. When my roast is complete, around 5-6 minutes, the air temperature has risen to around 385 degrees.
After I’ve roasted my beans, which tends to take around 10 minutes from start to finish, I quickly dump the beans into a strainer. There is a lot of papery skin that flies everywhere at this point. I pour the beans back and forth between the strainer and a Pyrex container, constantly shaking and wiping to remove any of the papery chaff.
Once the coffee is cool enough to touch, I leave it in the Pyrex and cover lightly overnight. This is to allow the initial carbon dioxide released from roasting to off-gas. Before the roasting process, incidentally, coffee can be stored somewhat haphazardly at room temperature and doesn’t have to be vacuum sealed. While green, the beans are hard like kidney beans and take a year or more to go stale.
Following the roast and overnight rest, I place my coffee in Mason jars where it continues to off-gas. The coffee smells and tastes great after about 3 days, if not closer to a week. Some suggest 24-48 hours, but I leave mine a bit longer. Leave the beans unground and it will maintain its smell and flavor for weeks, if not months.