helpful introduction to coffee roasting

helpful introduction to coffee roasting

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.


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 adapted 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 must also be prepared by 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?

The 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 are developed.

The content is the same; acids, proteins, and caffeine.

We’re talking about roasting coffee, but we are not looking for roasted coffee beans. 

The term “roast” means to roast, either in an oven or in a pan.

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

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 reduced to between 3 and 0.5 percent of the bean weight, depending on the degree of burning. 

The sugar content of the coffee beans is also affected during the roasting process.

It is the so-called Maillard reaction – reactions between carbohydrates and amino acids, which gives the product a “tan” in 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.

Very important in the culinary arts and very important in coffee roasting.

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.

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​

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

Then what 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.

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 is no universal standards.

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

Coffee roasted in the Western world is funny enough 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.

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 using a colorimeter. 

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” / popping that the burner listens to. 

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

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

When the beans are medium roasted, 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 controlled quickly.  

cooling the coffee beans

Almost as important as the burning is the cooling process. 

For the heat not to 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 the cups have found and which 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 of us, coffee lovers, into a new world through its uncompromising pursuit of the optimal result.

Does it sound like coffee roasting for you?

You know 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, ordering green coffee beans from different parts of the world, and combine them into a great cup of coffee.

I think it’s very comparable to running a microbrewery in the garage, except that coffee roasting does not require large barrels and so on… Just a small roaster on your kitchen counter.

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

Or if you are ready to get started on this fun, exciting hoppy, you can get yourself a new roaster below.

Photo Title Buy
Coffee Bean Roaster Machine for Home Use, Coffee Roaster Machine with Timing, 110V 1200W Find now on Amazon
Sandbox Smart Home Coffee Roaster Machine with Cooling Tray – Electric Direct Fired Beans Roasting For Home Use, Delivered via the App. 110V (Black) Find now on Amazon
JIAWANSHUN Household Coffee Roaster Coffee Roaster Machine for Home Use Made of 304 Food Grade Stainless Steel (110V) Find now on Amazon
Electric Coffee Roaster Machine, 0-240℃ Household Roasting Machine 1000G Coffee Bean Roasting Baking Machine For Coffee Shop and Home Use, Popcorn, Peanuts, Chestnut Sunflower Seed Roaster,110V Find now on Amazon

Here is a video of a man using one of the above-mentioned coffee roasters, and they make great coffee 🙂

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