Coffee roasting chemistry is the magic that tends to give the coffee beans ultimate aroma and flavor.  Roasting is the third part of a four-part work: cultivation, fermentation, roasting and preparation. 

Roasting reaction is the action of cooking, heating, and roasting in order to transform the green coffee bean into a roasted coffee bean. So, once again, we are at the beginning of a great story. So let’s wait for the roasting bible to come out and cross that fire barrier to get to the other side of the mirror.

Why is roasting important?

Roasting is arguably the most important step in making the perfect coffee. To your knowledge, untreated green beans have no aroma, but heat used on the roasting reaction can make several changes in the green coffee beans. Some of them are given below:

• They will lose some of their water and swell slightly;
• Their color will gradually change;
• The thermal decomposition of certain chemical compounds will help develop the aroma.

The result (i.e. the taste of the coffee) will however depend on the following parameters:

• The variety and geographical origin of the coffee; (altitude, type of soil, angle of the ground, sunshine, climate, humidity);
• Post-harvest treatment conditions;
• Roasting;
• The final preparation.

Without roasting, none of these steps could make it possible to obtain the aroma we know. Therefore, coffee roasting chemistry has a significant role in bringing the perfect brew to your cup.

Roasting stages

There are three main stages in roasting: drying stage, browning stage and development stage or roasting stage.

• Drying stage

Drying is very important before roasting the coffee bean as they hold humidity of 8-12%. This process typically lasts 4-8 minutes in a traditional drum roaster. This stage is very important as it helps the beans to gain much energy which can be used in the last stage of roasting reaction. A minimum of 160 degree temperature is required for this process.

• Browning stage

During this stage, the color of the beans changes to brown due to maillard reaction where sugar and amino acids are reduced which give rise to different aroma and color. In this stage, the first crack appears on the bean and the development stage begins.

• Development or roasting stage

Due to the exothermic reaction coffee breaks which gives a magical aroma to the beans. In this stage the coffee beans get their characteristic taste. However, if the development stage is not slowed down in the right time, the coffee beans can easily turn smokey and bitter in taste and flavor respectively.

Types of roast

Generally, there are four different types of roasts which are distinguished on the basis of color. The type of roast determines the overall taste of the coffee and the roasting reaction plays an important role in it. The four types of roasts are:

• Light roast

In order to obtain light mild coffee, the green coffee beans are not roasted for a long time. This short roasting doesn’t allow the oil to settle on the bean and thus, gives it a light brown color.

• Medium roast or American roast

Though the beans too have a non oily surface, however, the coffee tends to have a stronger flavour. Also, the color of the coffee is medium brown and is more popular among the people of the United States of America.

• Medium-dark roast

During the roasting reaction, some oil gets accumulated on the surface of the bean which gives it a much stronger flavor along with a slight bittersweet taste. Also, the beans turn out to be of rich brown color.

• Dark roast

After being  roasted for a prolonged time, the coffee beans achieve a shiny and oily surface which gives them a bitter taste. Also, the color of the beans turns black. However, it is proven that darker beans impart less acidic taste to the coffee.

To conclude

Coffee roasting is an art that requires dedication and knowledge in an optimum amount. Coffee roasting chemistry is really a very interesting topic as it is a story of a simple bean turning into something aromatic and flavorful. We hope that you liked our article and got to know everything about roasting.