Coffee roasting machine: types of roasters

What is coffee roasting and how does it work?

Coffee roasting is the process by which green coffee beans are transformed into what we know as coffee beans using high temperatures.

During a chemical process called the Maillard reaction (after the French chemist L.C. Maillard), a reaction occurs between carbohydrates and amino acids or proteins.

Atemperature of between 140 °C and 160 °Cactivates the sensory active compounds that give the coffee its unmistakable taste, aroma and colour.

However, when exposed tohigher temperatures, reactions occur which produce a number of carcinogenic compounds such as acrylamide, etc.

Roasting Spa Coffee |

Roasting coffee is a process that requires not only agood roaster, but especially a lot of experience and 100% concentration on the part of the roaster. This is despite the fact that modern roasters have electronics inside them that make the job much easier for the roaster's head and hands.

Theroaster can thus elevate aquality green coffee to thebest you have ever tasted. Or, with a little inattention, produce dozens of kilograms of coffee-shaped ash.

A brief history of coffee roasting

15th century roaster, Baghdad

Theproven history of coffee roasting dates back to the15th century in theMiddle East. There, coffee was roasted in small batches in roasters similar to large roasters over anopen fire. During this, the roaster stirred the beans with a second smaller spoon.

In the 17th century came the invention of thedrum roaster. The whole process was simplified and it was possible to roast more coffee at once.

The History of Coffee Roasting |

At the end of the18th century came gas and with it further improvements to the roasters of the time. And finally, decades later, it wasn't just coffee roasting that was revolutionised byelectricity.

In the 20th century, roasters were perhaps most improved by the invention of thefluid bed.

Since then, roasters have been changing, especially on the inside, incorporating more electronics, sensors, etc.

Types of fretboards

Today's professional roasters are divided into2 basic types:

  • drum roaster
  • hot air roaster

Drum roaster

Today's drum roasters are based on a concept invented hundreds of years ago. The whole principle is to roast the coffee in a large metal drum in which the beans are mixed like in a large slow blender. All this is placed above gas burners that ensure the high temperature required for roasting.

Thebeans are constantly stirred so that they are roasted evenly. Nevertheless, imperfections in roasting may occur in some beans. This is because some beans encounter the hot drum more often than others.

This problem is partly solved by the double drum roaster. This is because the drum in which the coffee is roasted does not come into direct contact with the heat source and thus remains slightly cooler.

Therefore, this type of roaster requires more care andattention from the roaster. However, if the roaster knows and operates his machine perfectly, you would be hard pressed to find unevenly roasted coffee.

Probat Drum Roaster |

Hot air roaster

Thehot airroaster as we know it today was experimented with as early as around 1926, but it wasn't until the1970s that thehot air fluid bed roaster saw the light of day .

Roasting Spa Coffee on a Giesen Roaster |

Theroasting system of the fluid bed roaster consists of blowing hot air directlyintothe green coffee. The coffee does not stay on the hot plate, but flies freely in the cylinder and roasts from all sides.

Theair temperature is constantly monitored and adapted to the roasting profile.

The advantage of these roasters is theeven roasting of all beans at the same time and the immediate removal of fine coffee skins. These are lighter than the beans themselves and are removed by the top end of the roller.

5 questions for the roaster of Spa Coffee Zdeněk Mareček

Is it possible to roast coffee exactly the same way twice? How can this be achieved?

Is it possible. Nowadays, the connection of the computer to the roaster helps us to do this. For example, we use theCropstersoftware to store roasting profiles, which we then repeat. So we have a profile of the temperature of the beans at a given time and then when we repeat this roasting, the coffee achieves the same taste.

How different are the machines used for roasting speciality coffee from those used to roast the coffee we can buy in the supermarket?

The roasting principles are the same. However, large roasters need a larger roaster (over 100 kg for a single roast). An adequate preview is the Starbuck's Roastery we visited in Milan. At Spa Coffee we use a 15kg roaster.

Is there any difference in the approach to roasting such two types of coffee?

Yes. Commercial coffee in the supermarket is usually roasted darker. The beans are often oily, which shows that the coffee has been exposed to a high temperature. Here, we try to roast the coffee more gently and represent its originality.

The roaster of Lázeňská kávy Zdeněk Mareček |

Are there any advantages in using a drum roaster when there is a hot air roaster with a fluid bed?

That is the question! I don't know the real advantages because I have never worked with a drum roaster. So it's hard to judge how it's better. In the end, though, it's more about the particular roaster who will be operating it. They have to get to know the machine, how it behaves and how it reacts to the different changes the roaster makes.

Anyway, there are some differences, no doubt. A hot air roaster is usually faster and one could say more gentle than roasting in a drum roaster.

Is it true that the use of drum roasters is predominant in Europe and hot air roasters overseas? Do you have any idea what the reason for that is?

They say. But I would say it's more a trend of the environment that people live in - what people see around them, they want to get. So if roasters in an area started out with hot air machines, then others who were just getting into the business were buying them.

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