How Does a Coffee Roasting Machine Work? Beancraft

How Does a Coffee Roasting Machine Work?

Posted by Meera Nair on

There was a time, hundreds of years ago when coffee was consumed as a beverage without even roasting the green beans. Obviously, it tasted nothing like the brews you can enjoy today.  

Historic accounts suggest that the resulting brew had a more earthy aroma and flavour profile but still packed a punch because of the caffeine and acidity. This is why Sufi mystics were known to consume the drink as it helped them focus for hours on end.

That said, can you imagine still consuming coffee decoction made with unroasted beans? Probably not! The coffee industry would not be where it is if it weren’t for the invention of coffee roasting machines. 

The Evolution of Roasting Coffee

The earliest edition of the coffee roaster consisted of a thin pan and metal spoon. The pan was placed on an open flame and the green beans were roasted by stirring them regularly to get evenly roasted coffee.

As you can imagine, it wasn’t the most comfortable method. The coffee roaster would have to deal with the fumes and heat as a great deal of attention was required in this hands-on method.

These issues were somewhat resolved with the invention of the cylindrical roaster. It was developed in the 17th century, allowing beans to be roasted within a cylindrical chamber that was externally heated. 

These machines also had a handle attached to the chamber, enabling the person in charge to simply rotate the cylinder and move the beans around. Within a few centuries, coffee roasters evolved from primitive to something far more functional. By the 19th century, commercial coffee roasters were being produced. 

Many of these were simply adaptations of the first cylindrical roaster. The main difference in some of these versions is that they had the ability to allow samples to be taken. Such innovation paved the way for modern-day coffee roasting, challenging roasters around the world to build their skills and create outstanding products.

how is coffee roasted

However, with bigger-volume coffee roasters came the hassle of handling large vessels that had just been heated to high temperatures. Over the next few decades, more and more features were added to the cylindrical coffee roaster to make the process of extracting the roasted beans safer and more efficient. 

Coffee machines that once operated within furnaces could now be adapted to function using electricity. The development of electric motors allowed producers to roast coffee consistently as well as have more control over the process and outcome.

How Do Coffee Roasters Work?

The basic stages involved in roasting coffee are drying, browning, development, and cooling. Even though green beans are usually dried before being sent for roasting, some percentage of moisture still remains in the beans.

Therefore, just before roasting can begin, the green beans go through a final drying stage in the coffee roasting machine. This stage typically lasts a few minutes.

Next, the browning stage is when the flavour compounds in the beans start to become more active. The colour of the beans also undergoes a significant change in this phase. To a certain degree, the drying of the beans continues into this second stage. Once the browning phase is over and the first crack of the beans is observed, the development stage begins. 

This is when the beans open up more and undergo further chemical changes to become flavourful and aromatic. They are no longer as dense as they were in the initial stage. 

The development phase varies depending on the roast level the producer is trying to achieve. For light roasts, the coffee beans are removed from the roaster shortly after the first crack. In the case of darker roasts, the roasting process is stopped around the time of the second crack.

Once the beans have been roasted, it is crucial that they are promptly removed from the machine and cooled down. This prevents them from getting roasted further and helps get them ready to be packaged. Large trays with a cooling fan are used in this final stage of roasting.

Types of Coffee Roasters

There are primarily two types of coffee roasting machines - drum roasters and air roasters. 

coffee roasting & cooling

Factors like temperature, time, and airflow affect the roasting process and how each of these machines operates. 

A drum roaster can be a single-walled or a double-walled one. Beans are dropped into a rotating drum that has been heated. In this scenario, beans get roasted not only because of the temperature of the surface of the drum but also by convection (as in the case of a microwave) because of the heat maintained within the drum cavity.

Drum roasters are most commonly used by coffee producers because of their features and the ultimate flavour profile that they deliver. 

On the other hand, an air roaster is a machine where hot air is passed through a chamber and into the roaster, making the coffee beans tumble around inside the roasting compartment. Think of the coffee beans as fighting gravity and floating on hot air - you’ll be visualising what goes on in an air roaster. 

Also known as the fluid bed roaster, this machine is far more energy-efficient and ideal if you want to retain the origin flavour of the coffee, but the costs that it incurs and the effort required to maintain the machine often outweigh the positives. 

Ideally, drum roasters are perfect if you prefer darker roasts, and an air roaster is suitable for lighter roasts. 

Either way, there are pros and cons to each of the machines. It entirely depends on the budget, capacity requirements, and other preferences of the coffee producer.

The taste, mouthfeel, and aroma of roasted coffee are pleasing to our senses. So much so that it has become a crucial part of our lifestyle. 

Explore the blog section of our website to learn more about coffee roasting and the roast level that is perfect for you.

For coffees that have been roasted to achieve a balanced flavour profile, check out our single origins and blends.

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