helpful introduction to coffee roasting

Introduction To Coffee Roasting

Coffee roasting is extremely important to create a flavorful cup of coffee.

The aroma of coffee is something very special. About 1000 different aromatic compounds are hidden inside a coffee bean – more than 850 are known. Through the burning process, these are released.

Here’s all you need to know about coffee roasting:

It is the Taste That Counts

There are many ways to roast coffee, and there is no general standard. 

The coffee beans are different and must be processed accordingly. 

Both time and temperature are adjusted according to the raw materials you have. An experienced coffee roaster can make coffee with different aromas from the same batch by controlling time and temperature.

Ultimately, it is the taste that counts, and the taste preferences are different. 

Coffee is also prepared through various methods, which are taken into account when roasting. The coffee distilleries develop their own profiles and try to find their style.

Craft traditions run deep, whether it is large-scale industrial production or micro-production in small distilleries. 

It is about getting the most out of the raw materials you have through a controlled process.

What Happens During the Coffee Roasting Process?

Coffee beans are the seeds inside a ripe, red stone fruit from the coffee tree. By carefully burning these green beans, the physical and chemical properties of the beans change. 

They expand and change the taste, color, and smell – flavors and aromas develop. The content is the same; acids, proteins, and caffeine.

Roasting can be done either in an oven or in a pan.

In the roasting process, the coffee beans undergo several chemical reactions. 

Loss of Moisture

The most obvious change at such a high temperature is the loss of water content (moisture). Water makes up between 8-14 percent of the weight of raw coffee. 

After burning, the water content is decreases to between 3 and 0.5 percent of the bean weight, depending on the degree of burning. 

Maillard Reaction

It is the so-called Maillard reaction – reactions between carbohydrates and amino acids, which give the product a “tan” for the lack of better words. The color of french fries, chips, fried buns, crust, beer, brown cheese, and caramel comes from the same chemical reaction.

One thing is the color, but perhaps more interesting is that the Maillard reaction forms hundreds of different aromas. It is quite important in the culinary arts as well as in coffee roasting.

Change in Density

During the roasting process, the density also changes. Moisture disappears, weight decreases but volume increases. The beans expand close to 50%.

We calculate a burning loss of 15% for lightly roasted coffee and 19% for dark roasted coffee.

Heat Changes

In the beginning, we have a so-called endothermic process where the beans absorb heat. When the beans reach around 175 °, an exothermic reaction occurs where they give off heat.

For the coffee roaster, it is necessary to follow, as this means that the beans heat themselves. An adjustment of the temperature may be necessary.

Coffee Roasting Grades

Coffee Roasting Grades​

For how long the coffee is roasted and at what temperature depends primarily on the type of roasting equipment you use. 

Then whichever taste profile you want the finished coffee to have.

If the coffee is roasted too little, the taste becomes raw and Emmen. If it is roasted for too long, the taste can become tight and bitter.

Unfortunately, roasting coffee too dark is often used to camouflage poor coffee quality.

Degrees of Roast

Internationally, coffee producers often have names for the different degrees of roasting, such as Light Roast, City Roast, Full City Roast, French Roast, and Italian Roast.

However, there are no universal standards.

The roasters often follow their own recipes and often make their own blends.

Coffee roasted in the Western world is usually lighter roasted than for example in Asia or the Middle East.

Light roasts highlight the acidity of the coffee and any fruity flavor components.

Darker roasts give more fullness and sweetness but also more bitterness and less acidity.

When roasted too dark, the coffees lose their distinctive taste characteristics.


The temperature when the coffee enters the burner is normally around 200 ° C. It can be both higher and lower. 

Then the temperature drops to between 100 and 150 ° C.

Gradually, the temperature rises, and here, the burner can adjust concerning its own profile. 

The roasting time is generally between 10 and 20 minutes.

Factors Affecting the Roast

Many factors help the burner decide which profile is best suited. 

The profile is shown on a graph, with time on one axis and temperature on the other. 

Larger roasteries control this using computer programs and sensors inside the roaster.

You can judge the degree of the roast by looking at the color of the beans either with your eyes or by using a colorimeter. 

Visual Changes

As the beans absorb heat, they change color from greenish to yellow and then to darker shades of brown. 

If you continue to roast them, you will see oil on the surface of the beans. 

Color is not enough, both sound and smell are important to the burner while monitoring the process.


Sound is a good indicator of bean temperature during the roasting process. 

There are two temperature thresholds called “cracks” or popping that the burner listens to. 

First, the beans will crackle like popcorn does when it pops, only calmer. 

This point is the “first crack”, which marks the beginning of the candle burning. The beans have then increased in size by 50%.

When the beans reach medium roast, they give off a “second crack.” 

This is the midpoint between medium and dark burning.

Between the first and second cracks are considered as a good time to stop the roasting, if you are looking for a nice mid-range coffee.

If you, for example, want to make an espresso, you would leave it longer and get a darker roast, ad thereby a stronger tasting bean.

peanut coating machine

Coffee Roasters

There are several types of incinerators, but the most common are either drum or hot air-based. 

The drum machines consist of horizontally or vertically rotating drums that dry the green coffee beans under the influence of heat. 

In hot-air roasters (flat-bed, fluid-bed), the air is inflated through holes in the bottom of the combustion chamber.

In this way, the beans will circulate and stay “liquid” and will not come into direct contact with the metal for a long time.

When it comes to the heat source, most people prefer gas, as it can be easier to control.  

Cooling the Coffee Beans

The cooling process is almost as important as the actual burning.

For the heat to not develop inside the beans, the roaster must quickly take them out of the roasting apparatus and ensure rapid cooling within 2-3 minutes. 

This is done using air or a water shower.

Small and Large Coffee Roasters

The large coffee roasters can produce several tonnes per hour, and the coffee often comes on the market as so-called blends (coffee blends). 

Whether you drink from large roasters or small local roasters, all roasts will be the result of carefully composed mixtures that they have found and should be as similar as possible over a long period of time.

The small coffee roasters produce blends to a lesser extent. The volume is small in relation to the total coffee production but is still of great importance.

A handful of coffee roasters led by dedicated enthusiasts has lifted all coffee lovers into a new world through its uncompromising pursuit of the optimal result.

Is Coffee Roasting for You?

Surprisingly, coffee roasting is a cheap and gratifying interest.

Personally, I love roasting coffee, and I believe that I have learned to appreciate coffee more through my journey as a coffee roaster.

It’s fun to try to make your own coffee blends. The whole process of first ordering green coffee beans from different parts of the world and combining them into a great cup of coffee is wonderful.

I think it’s comparable to running a microbrewery in the garage, except that coffee roasting does not require large barrels. All you need is a small roaster on your kitchen counter.

If you would like to try, I recommend checking out our article to get some more information.

Or if you are ready to get started on this fun, exciting hobby, you can get yourself a new roaster. Here is a video of a man using one.

Hopefully, by the end, you learned more about coffee roasting than you knew before.

As mentioned above, you can give it a try on your own!

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