Roasting

Want to learn more about the roasting process? Maybe even dabble in it yourself? Here's a quick overview on the different stages of the roasting. Who knows? Maybe you've found a new hobby!

Bean Color & Roast Level

Green coffee beans experience significant color change throughout the roasting process. They will transition from green to yellow, then to the hues of brown we all recognize as coffee. The color change is due to the caramelization of sugars in the bean thanks to Maillard reactions. Finally, the beans will transition from brown to black as these sugars begin to burn.

In terms of flavor, there is an inverse relationship between origin flavor and roast flavor. Essentially, lighter roasts tend to have more origin character and as you progress through the roast the origin flavor is eclipsed by the roast character. It is an art finding the delicate balance between the origin and the roast.

Green Beans

Green processed beans typically contain around 10% moisture. Depending on the origin they will have subtle differences in smell but they will mostly smell earthy and are much smaller than roasted beans that you'll be familiar with.

Yellowing

The heat in the roaster takes a while to penetrate the beans. If the roaster has a temperature probe within, this can be observed by a drop in temperature when the beans are charged into the roaster (typically preheated). The temperature will steadily rise as the beans take on heat which will result in the first color change accurately named "yellowing" since they turn well... yellow.

First Crack

Remember back when I mentioned that green coffee beans have around 10% moisture in them? As the beans absorb heat from the roaster, their internal temperature rises. This causes steam, as well as some other gasses from the roasting process, to build pressure within the bean. Once the pressure reaches a point where the bean's structure can no longer hold this pressure, the bean will crack audibly as the pressure forces the gasses to rupture the bean and escape. This cracking sound resembles popcorn popping. The first crack marks the transition from the early stages of roasting to the flavor development stage. Light roasts are usually stopped shortly after the first crack. 

End of First Crack

Once the beans have stopped their audible popping and some time has elapsed for the beans to expand, develop an even color, and shed their chaff (cellulose cover), the roast will be nearing the end of first crack. This is where city and city+ roasts will stop. These are typically considered medium roasts.

Second Crack

If the roast is continued, the roast will reach second crack. Full City roasts are stopped right before second crack and Full City + roasts are stopped right at second crack. Once second crack is achieved the roast level is usually now considered a dark roast.

End of Second Crack

Second crack is very quick and if the roaster is not paying close attention they can easily burn the beans and ruin the batch. Beans that have been roasted past second crack develop an oily sheen on them due to the breakdown of the bean's internal structure. Vienna and French roasts can be found beyond second crack.

Like what you see?

Whether you're looking to get into roasting your first batch or you're a seasoned pro, these are my roaster recommendations for the home roasting aficionado.

Starter Roaster?

Its always best to start small with a new hobby, that's why I recommend using what you already have in your kitchen if you're thinking about getting into roasting. An air fryer or popcorn air popper can make great roasts with minimal investment!

Level Up!

If you're looking to step up your coffee roasting, you probably want to look at the Aillo Bullet. Its my dream home roaster. Drool.