The Art and Science of Coffee Roasting
(Photo : Andrew Neel via Unsplash)

It reacts differently with each blend of science and art. The skillful execution is essential because it transforms the green coffee bean into the drinkable beverage most people enjoy.

When applying heat to coffee, hundreds of chemical reactions coincide. That is why most professional roasters have accurate and precise recipes, even those experimenting with beanless varieties and other innovations. The beans have the same components as raw food, and they metabolize the same way when heat is applied.

Roasting requires some skills and knowledge; the one in charge must be accurate to provide incredible coffee profiles. With that said, here is a quick look at the art and science of coffee roasting.

1. Drying Phase

From the commercial coffee roaster found in your local cafe to the industrial-grade roasteries used by Folgers and friends, the basic science is the same. Before the beans are roasted, they are green or yellow with a fruity or grassy smell.

At this point, they don't necessarily have the flavor and taste most people crave; that is why they must be roasted. The first few minutes of roasting are called the drying phase or color change. The roasting master will deposit these seeds into a pre-warmed roaster. They will heat up quickly until they reach an equilibrium with the roaster's temperature.

The roasting experts are trained to do what they do. That makes up the art part of it; they have to make roasting decisions quickly. They are the ones who determine the flavor of every batch. It's a significant role because they can destroy the whole batch if they mess up one aspect.

As the roasting process happens, the expert will be inspecting the circulating beans. They begin to change color to light brown and produce a sugary smell. The aroma will become more nutty and toasty as the beans expand and crack.

Roasting falls into four main categories; there is dark, medium-dark, medium, and light roast. Each one has a different flavor and color. You have to determine which flavor you want before you start the process. It will help you decide the amount of time you need to roast the beans.

2. First Crack

The first crack is pivotal for the roasting process because the coffee beans become exothermic. They start generating their own heat. The first crack usually happens between 385-390 degrees Celsius.

That is where the water escapes, the sugar caramelizes, and pressure builds up inside the coffee bean forcing its surface to crack. At this point, you can consider the roasting process complete because you turn off the roaster and allow the beans to continue roasting with the self-generated heat.

However, this is where roasting artistry comes to play. The roaster will determine if they should continue experimenting to get more variations and flavors or remove the beans. If the intention was to get a light roast, they could stop at this stage.

Different coffee beans behave differently when the heat is turned off. You have to remain vigilant and observe the beans until they attain the color you want.

3. Second Crack

When you leave the seeds in the roaster long enough, they will move from a chocolate brown to nearly black. That is where you achieve French, Italian, and Spanish roasts. These are the darkest beans used to make coffee.

However, you will mainly taste the roast and not the bean at this point. When you hear the second crack and are satisfied with the results, get the beans into the cooling tray. The second crack will sound like rice krispies, not the popcorn sound you heard with the first crack. If you roast past the second crack, tiny explosions on the bean will create little pits on the surface.

The roaster has to determine when the optimum color and roast is achieved and quickly release the seeds. Timing is everything; a minor delay can alter the flavor of the coffee beans. Over-roasting will create a bitter, black and unpleasant drink. Where science ends, the art begins. The artist, in this case, has to produce delicious dark, medium, or light coffee beans.

Final Thoughts

Roasting coffee transforms green beans into different coffee products. The process requires a lot of precision to allow the chemical reactions to occur. The heating and timing have to be right. A good roaster will think about the age of the beans and how dark they want the beans to become.

To maximize sweetness, you have to minimize the caramelization process. When your tasting compounds thermally degrade, you will have bitter seeds. The devil is in the details when it comes to roasting.

So whether you're drinking coffee for its health benefits, for added energy to get through the day, or because you love the flavor, now you know that there's a lot more to coffee beans than you may have ever imagined!