Somehow we've found ourselves back in the classroom, studying geography, climatology, chemistry, and statistics. The roasting process is tricky, but we are not intimidated. Fostering green coffee beans to create a beautifully-brown roast that can be ground and brewed to perfection is, well, complicated. Some insight...
[Sidebar, if you are a coffee expert and reading this, you may judge us as novice and inexperienced. We don't care. We are farmers serving coffee to farmers--for us, this isn't a sophisticated process. So, if this reads as a clunky, coffee hack, this is likely not the coffee for you. Back to the fun...]
It starts with geography--we've now sampled beans from four continents, across several latitudes and altitudes. The make up of each bean varies according to where, how and at what climate it was grown. Being farmers, we get this. Some of these variables are controllable, and others are not--that's the interesting part. Some beans arrive greener in color than others. Some are super small. Some smell like soybeans (wet and musty), while others smell like chocolate or flowers. None smells like coffee.
When you add heat, all of these characteristics matter. And, as we learned on the first batch, how heat is applied (temperature climb, intensity, distribution, and removal) also matters. We absolutely burned the first batch, cranking up the heat and driving the roast as far as we could just to hear the *cracks*. Oops.
As it turns out, coffee beans pop like popcorn. Each type of bean cracks at a different temperature point--for most of our beans that happens when the bean temperature reaches approximately 385-degrees f. What is happening during the cracking is an internal chemical reaction involving acids, proteins, sugars and caffeine. In short, it's the SPARK that makes coffee beans taste like coffee. The cracking sound is louder and lasts longer with some beans than others. The beans expand in size--dramatically--and look more like those you buy in the store. If you stop at this point, the beans are light roasted.
IF you keep adding heat to the beans, however, you will turn your beans into a medium roast. They start to smell differently as the sugars cook and you turn the corner on 400-degrees f. Here's where we get nervous in the process. No distractions at this point. Bringing the temperature up carefully from 400- to 425-degrees f. can happen very quickly and can make or break the roast. Stopping at this point provides a nice, light-brown bean that is matte and likely very flavorful. This is an ideal roast profile for some geographic beans. Some call this an "American" roast. Others may refer to it as a "City" roast.
Taking the beans one step further to 425-degrees f. and beyond... this is my favorite part. I love dark roasts, and that's what we're about to produce here. It only works well for some beans, those that can tolerate the heat. We've found great success with the Ethiopian, Columbian, Sumatran, and Rosebud varieties. At some point after 425 (again, this temperature threshold varies across beans), there is an audible second *crack*. This time, the popping sounds more like the snapping of Pop Rocks candy in your mouth or Rice Krispies cereal in a bowl of milk, if you've ever had those experiences. The cracks are rapid and happen very quickly relative to the first cracks. At this point, more chemical changes are happening inside the beans resulting in the release of natural oils. These oils seep out over time, coating the dark roasts with a shiny or oily film. Note: the longer your beans rest after roasting (we tend to prefer resting for 4-7 days before tasting the fresh roasts), the more the natural oils will ooze out and coat the beans. This explains why Starbucks espresso beans are so shiny--they tend to roast to super-dark, which draws out significant oil and shine.
The time after the beans have reached full second crack is the most delicate/fragile point of the roasting process. The beans start to smell burnt after second crack and may even smoke. To prevent burning, we take the beans out of the roaster and try to cool them very quickly in a cooling bin. Stopping the roasting quickly will hold the beans to a nice, dark roast. If you bag these after they've cooled in an airtight container and allow them to rest even just overnight, the smells in the morning are heavenly. The same goes for lighter roasts, but we've found they take longer to rest and for the flavors and smells to develop.
So far, we've found magic in the process for some of our beans. Fan favorites include the medium-dark-roasted Ethiopian Yirgacheffe and Costa Rican varieties and the dark-roasted Rosebud espresso. Our Colombian Supremo can be held at a medium (just to the start of second crack). We're currently experimenting with Brazilian and Sumatran--each unique from green to finish. We feverishly update our roasting notes with each batch we roast.
Each day we have the opportunity to experiment in the "lab" is an adventure, discovering hidden elements in each bean. And, we can't wait to send these geography-climatology-chemistry experiments out into the world for tasting. We're getting closer, and we're crossing our fingers for above-average lab grades...