What You Need to Know About Coffee Bean Roasting

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If the brewing process is to perform magic on the roasted coffee, then the roasting itself shall be called magic along. Dating back to 1650, ancient coffee pioneer try the first cylinder roaster with a crank to heat the bean and try to make it flavor out of the green little bean. Nowadays, the food industry has evolved into a new era. Roasty process has become complicated. But getting the knowledge of coffee bean roasting will help you make a better choice.

The process is complex, however, it is also simple if we only consider the flavor part of it. Because we can exclude anything that is complex but is not directly related to taste itself and only leave the aroma part.

The Outline

A good taste of a cup of coffee depends on the quality of green beans, the roasting condition, roasting profile selection and the brewing process. There are more than 800 compounds in the roasted coffee. However, only 30 compounds are responsible for the main flavor of a cup of coffee. Therefore the outline of the roasting shall be started before the roasting process because our main ingredient is the bean itself. The whole process is a balance of aroma and acid.

Pick Green Bean => Roasting Profile Selection => Roasting => Dry => Package.

The Green Coffee Beans

Green beans are from the bright-red coffee cherries. It is the seed of the cherry. Well, they are picked and sifted by their quality. So how to judge the quality? Here is the answer. The bean size, color, shape, method of dring, crop year and presence of defects are all counted to the quality of the bean.

There are many species of coffee beans but only Coffea Arabica(Arabica), Coffea canephora(Robusta) and Coffea liberica are mainly for commercial usage. Arabica has the largest portion of world production. Approximately 70%. And Robusta accounts for about 35%. Arabica has better quality.

Arabica is hard to grow and hence has a high price. The opposite, Robusta is easy to grow and has a lower price. Factory who roasts coffee will often mix Robusta with Arabica to make a better cost control. However, this doesn’t mean taste will be harmed. In contrast, it is balanced.

Green coffee beans have very minimal flavor. If you happen to get some of it, the smell will be nothing like coffee. The fresh taste of it will make you doubt whether they are coffee beans. However, upon roasting, the aroma of coffee will be developed.

Remember I have told you that Arabica is considered as the better quality? Because Arabica beans generate the aroma effect. The Robusta beans have stronger “roasty” and “sulphury” odor. Combing them together, the blend will produce a balanced taste.

Those green beans need to be dried out before roasting. They shall be dried to 10-14.5% moisture content. After drying, beans will be stored below 78 ℉ ( 26℃ ) in the dry environment. The beans could be stored for more than 3 years under optimal conditions.

The Process and Outcome

Now that you know much about the beans, it is time for you to understand the process of roasting now. It is what makes your coffee beans into aroma coffee beans.

What Changes During the Roasting

Chemical composition of green, roasted, and brewd coffee

As you can see from the figures above, the roasted coffee will have less water and more CO2 inside the beans. Less water will make the solutes in the beans more easily to be dissolved in the water. Another benefit is to get less weight. I think you will be surprised that what you drink is just a very small part of the coffee beans.

There are two cracks during roasting. During the first crack, the cellulose cell wall will be broken. Water will escape. And then as the heating continues, the coffee will be darker and the CO2 buildup will exceed the cellulosic walls of the coffee. That’s why you will see less water and the CO2 in the roasted bean.

The quality of the roasted heavy depends on the roasted process and the roasting profiles. So even the substances remain the same. The flavor will be different from varies roasted coffee suppliers.

Light, Medium and Dark Roasts

Now comes the most important part of the roasting process. Depending on the extent of the heat treatment, coffee can be categorized as light, medium or dark roasts. Let’s talk about the difference between them.


  • Light roasts tend to give sour, grassy and underdeveloped flavor
  • Medium roasts will serve a balanced taste and aroma with citrus flavor.
  • Dark roasts present low acidity sensory profiles.


Well, someone may tell you roasting process will change the caffeine ratio. That’s true. But the difference is so little that you cannot even notice it. So there is no difference between light, medium and dark roasts bean.

What It Means to Choose the Right Bean

The answer is simple for choosing the right bead.

Firstly, since we have randomness in the cropping seasons, like weather conditions, so don’t expect to get the same flavor in different years. They vary, but not too much. But to remember, if you like the aroma of the coffee, choose the one with more Arabica beans.

Secondly, different roasted coffee beans will have almost the same caffeine ratio. Therefore, if you want low caffeine beans, just directly go to decaf. Don’t waste your time choosing between the roasted colors.

Third, I have summarized a table for you to choose the right flavor. Different people have different taste, you can choose the one you want based on your needs.

Roast DegreeFlavor and Characteristics
LightLight brown color. Sour, grassy and underdeveloped flavor
MediumMedium brown color. A balanced taste, with both some acidity and good coffee aroma.
DarkDark brown color. Low acidity and minor aroma.

Fouth, since the different brands will have different roasting profiles, so just go and experiment with your taste. Even for the same roast, like medium, you will still find a huge difference for the aroma.

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