What is coffee roasting?
- The Five Distinct Stages
- Creating Different Roast Levels
- Its Role in Coffee Extraction
- Increases Solubility
- Progression of Flavor Compounds
What is coffee roasting? For coffee enthusiasts, it’s a fascinating topic, and for good reason. The roasting process involves the transformation of a coffee cherry into the complex and diverse coffee beans that we grind, brew, and enjoy every day. In this article, we explain why this process is important to enjoying a great cup of coffee.
The Five Distinct Stages
After harvest, coffee is considered “green,” which means they are still in their raw, soft forms. Roasting is the process that transforms them into the beans that most of us are familiar with — browned, slightly cracked, and with the aroma of coffee.
Roasting is an attempt to bring the beans to a specific level of development through careful heating. While the ideal conditions will differ based on the kind of coffee, any bean can go through five distinct roasting stages:
- Drying or Yellowing — A crucial stage that is determined by the initial moisture content of the beans. This is where the beans begin to turn yellow and smell almost hay-like.
- Maillard Reaction — Where the coffee starts to ‘brown.’ This reaction triggers the formation of several chemical compounds that evaporate into the air, contributing to the aroma.
- First Crack — While earlier stages are all about heating the outer shell of the bean, the first crack is all about the heat building up inside the bean. This is where the pressure from evaporation and heat begins to break the bean down from the inside out. This reaction produces an audible popping sound.
- Second Crack — Darker roasts go through a second cracking phase, which indicates that the beans are nearing a full breakdown.
- Carbonization — This is where the beans fully break down, which needs to be avoided.
Creating Different Roast Levels
As roast time increases, different roast levels are achieved. In general, there are 4 types of roasts: light, medium, medium-dark, or dark. There is a whole world of difference between each level, and the ‘perfect’ one is a subjective choice.
Light roasts — Light roast coffee has a light brown color and no oil on its surface. Light roasts have an internal temperature of 176-204 °C at their roasting peak, barely reaching the first crack. Other names for light roasts include:
Medium roasts — Medium roast coffee has a medium brown color and a non-oily surface. Medium roasts hit an internal temperature of 204-221 °C at their roasting peak, typically putting them past the first crack, but before the second. Medium roasts are also called:
Medium-dark roasts — Medium-dark roasts have deeper brown colors than medium roasts, with some oil on their surface. Medium-dark roasts reach an internal temperature of 225-230 °C, which happens during or right after the second crack. This roast is also known by the name ‘Full City’.
Dark roasts — Dark-roast coffees are roasted past the second crack, with peak internal temperatures of around 240 °C. This is as far as you can go without ruining the bean. Dark roasts are also known as:
Its Role in Coffee Extraction
Roasting is what brings out the intrinsic flavors and aromas that are locked inside a raw, green coffee bean. While it is still green, coffee beans have a grassy smell and little to no taste. The roasting process causes numerous chemical changes to take place within the bean.
The sugars, starches, fats, and oils within are emulsified, caramelized, and seep out of the bean when exposed to high heat. When they reach the ideal conditions, they are quickly cooled to stop this heating process. Roasting your coffee beans extracts the sweetness, bitterness, and other unique attributes intrinsic to the region and varietal of the bean.
Coffee roasting not only brings out the aromas and flavors but also increases the solubility of coffee beans. As the roast develops, the beans become more soluble in water.
But why is this a big deal for coffee? Because it is the essential element in the brewing experience. The level of solubility for a specific roast is the key factor for achieving the right extraction of coffee attributes. Some coffees taste better with more solubility, while other coffees flourish with less solubility. Solubility is also a major influence on the ideal brewing conditions of water temperature, brew time, and grind size.
Progression of Flavor Compounds
As previously mentioned, roasting causes a compound breakdown within a coffee bean. This breakdown not only determines solubility, but also the progression of the coffee's flavor. As the roast progresses from lighter to darker, the flavor of the beans becomes more or less pronounced.
Light roasts often have crisp acidic qualities (such as citrus, malic acid, and apple-like flavors), and a mellow body. Medium roasts can develop medium acidity, a balanced body, as well as nut and chocolate-like flavors. Darker roasts can bring out a heavy body, deeper flavors, and deep caramel sweetness.
The best level of roasting depends on the coffee bean’s origin, varietal, and other factors. A roaster has to carefully hit the ideal heating conditions and stop the roasting process at the right time to showcase a coffee’s natural flavor profile.
Many coffee beginners ask, “What is coffee roasting?” when diving into the complex world of specialty coffee. To put it simply, coffee roasting is one of the most influential factors of coffee quality and taste. It is a precise, ever-developing art that transforms the simple green bean into an aromatic and flavorful coffee.
From humbly preparing coffee beans in a home kitchen, Plain Sight Coffee Roasters have developed their roasting into the refined process it is today. We continue to train and improve our roasting process to create our specialty coffee products. Click here to check out our selection!