Everything you need to know about the classic drum roaster

Esther Gibbs
September 27, 2022
Everything you need to know about the classic drum roaster

Transforming coffee from a green seed into a complex and flavoursome brown bean relies on the act of roasting.

Depending on the roasting method used, the flavour of the coffee can be altered drastically.

While there are many methods to roast coffee, one of the most traditional and prevalent ways is to use a drum roaster. Essentially, this process uses a large, cylindrical metal drum that rotates while heat is applied to the outside.

Typically, a drum roaster is easy to control and manipulate. Depending on the system, roasters can alter many elements of the roast, such as airspeed, heat application, and drum speed.

Traditional drum roasting uses a conductive heat transfer to bring out the carbohydrates and oils within the coffee bean. The result is often a thicker, denser flavour and aftertaste.

To learn more about the classic drum roaster and why it is so popular, I spoke with the owner of Lucid Coffee Roasters, Stephen Houston.

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An image of a drum roaster roasting coffee in an article about drum roaster

Why are drum roasters the most common way to roast coffee?

Many roasters will have their preferred method for roasting coffee for various reasons.

It is important to note that each roasting method will have its pros and cons. For instance, some roasters may prefer a fluid bed roaster because of its consistency and “cleaner” flavour due to the reduced conductive heat transfer.

“I would say drum roasters are the most common because of their ease of use,” explains Stephen, who is also a vice chair of the Specialty Coffee Associations Coffee Roasters Guild. “More so, they may be cheaper to make than some variations of air roasters,” he adds.

Stephen Houston, owner of Lucid Coffee Roaster roasts on a Diedrich IR12
Stephen Houston, owner of Lucid Coffee Roaster roasts on a Diedrich IR12.

As a result, drum roasters tend to be the most affordable option for many coffee roasters. Depending on the brand, prices can range from £5000 for a 2kg (4lbs) drum roaster to £60,000 for a 12kg (26lbs) state-of-the-art, fully automated drum roaster.

Alternatively, fluid bed roasters are often more expensive, starting at around £25,000 due to the technology they use.

Drum roasters may also be a popular option because of the range of variables that can be used to control the roast.

“Drum roasting is heating coffee beans in a single or double wall drum, with a direct or indirect heat source that is usually gas powered,” Stephen says.

This drum rotates at a steady pace of revolutions per minute (RPM), tossing the beans up into the air and distributing the heat. If the drum’s RPM is too slow, the beans may become scorched.

Drum roasting tends to use three heat exchanges: conduction, convection, and radiant heat. Conduction helps with the development of the coffee, the caramelisation, and the final colour.

Convection ensures an even roast throughout the inside of the bean, ensuring the chemical reactions happen correctly and a successful drying and Maillard reaction.

Although it does not specifically develop flavours, radiant heat supports the overall efficiency of the machine as well as the transfer of heat during roasting.

“Drum roasting differs from other roaster styles as it offers not just convective heat from the airflow, but conductive heat from the drum itself,” Stephen says. “This provides many benefits, as well as a few problems if not used correctly.”

With drum roasting, the heat, airflow, and drum speed can be changed throughout the roast to manipulate the energy transfers.

An image of a coffee roaster inspecting roast coffee in an article on drum roaster

Should roasters invest in drum roasters?

Drum roasters provide opportunities for roasters to create unique flavour profiles to get the most out of their coffees.

“‘I believe drum roasters give you the best balance of using conductive and convective heat transfer,” Stephen says. “To me, this can increase solubility and keep a great balance in your coffee flavour profile. I also find them easier to work with as they provide great flexibility!’

By altering variables such as heat, drum speed, and airflow, it is possible for roasters to experiment with each stage of the roast.

For instance, if a roast tastes underdeveloped and grassy, roasters can increase airflow early in the roast. Alternatively, if the flavours are smoky, roasters can increase airflow towards the end.

More so, roasters can reduce the drum speed to increase conduction and caramelisation to give the beans a darker colour without affecting internal development.

Drum roasting also allows roasters to conduct a sensory evaluation by hearing the first crack and smelling the stage of the roast. Additionally, roasters can choose to use a trier, or sample spoon to observe the physical changes in the beans.

While a drum roaster offers consistency, it does require the roaster to be consistent. This includes managing between batch protocols to ensure radiant heat is maintained.

Multitasking while using a drum roaster should be avoided. Even with a preset profile, roasters should keep watch to make sure the machine is reacting in the same way and heat is transferring as expected.

The smallest changes in a roast will impact a flavour. Thankfully most roasters can use a number of data capturing apps to help them stay in control of the roast.

An image of Lucid Coffee Roasters sustainable packaging in an article on drum roaster

To ensure his hard work and care is transferred to his consumers, Stephen packs his roasted coffee in custom-printed, sustainable coffee bags.  

At MTPak Coffee, we offer a range of 100% recyclable coffee packaging options made from renewable materials such as kraft paper, rice paper, or multilayer LDPE packaging with an environmentally friendly PLA lining, all of which minimise waste and contribute to a circular economy.

More so, we give our roasters complete control over the design process by allowing them to build their own coffee bags. Our design team is available to help you create coffee packaging that reflects your brand and commitment to providing quality coffee.  

Plus, we are able to custom-print coffee bags using innovative digitally printing technology, with a quick turnaround time of 40-hours and 24-hour shipping time. 

MTPak Coffee also offers low minimum order quantities (MOQs) to micro-roasters who are looking to remain agile while showcasing brand identity and a commitment to the environment.

For more information on sustainable, custom-printed coffee packaging, contact our team.

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