Understanding coffee roasters – Fluid bed roasters

Yker Valerio
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July 14, 2023
An image of a coffee roaster using a fluid bed coffee roaster, air coffee roaster, roasting coffee with an fluid bed roaster, in an article on fluid bed roasters

Transforming green beans into the aromatic coffee loved by millions depends on one vital piece of equipment – the coffee roaster. Today, drum roasters are the most popular machine for professional coffee roasters around the world. 

However, in the past few decades, some manufacturers have started looking away from drum roasters in favour of an alternative model. Fluid bed roasters, also known as air roasters, are becoming increasingly popular – despite the technology being available since the early 1970s. 

To gain a better understanding of fluid bed roasters and how roasters can benefit from using them, I spoke with Ken Lathrop from Coffee Crafters, a fluid bed roaster manufacturer, and coffee roaster Emilio Inda-Díaz of Origen Cafe Tequepexpan.

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History of fluid bed roasters

The history of fluid bed coffee roasters dates back to the early 1900s, when the process was first used to dry magnesium pellets. Chemical engineer Michael Sivetz filed a patent for the first commercial fluid bed roaster in 1976.

Considering that air roasters are often cheaper than drum roasters, it is surprising they aren’t more popular. The reasons behind this are unclear, but innovation adoption isn’t entirely rational. John T. Gourville explained it in a Harvard Business Review article about new product adoption.

Overall, Gourville states people are more reluctant to invest in a new product when it requires changing behaviour and learning new skills. This is particularly true when the user experience is different from the status quo.

“I believe fluid bed roasters are less popular because they are relatively new to the industry,” explains Ken. “Early models on the market lacked the fit and finish to compete with the well-established drum roaster brands.”

An image of a fluid bed roaster roasting coffee beans, air roaster, fluid bed coffee roaster, in an article on fluid bed roasters

Understanding how fluid bed roasters work

The main difference between fluid bed roasting and drum roasting is how the heat is transferred to the bean.

Heat transfer

Fluid bed roasting uses convection,” Ken explains. “This is where the bean is introduced to heat through hot air that is circulating consistently through the bean mass. Adjustments in heat and airflow happen instantaneously in this roaster. With the addition of computerised heat control, the Rate of Rise (RoR) on a roast profile can be very accurate,” he adds.

On the contrary, conduction is the transfer of heat through direct contact. In a drum roaster, the metal drum is heated, which then transfers heat to the beans. 

Convection often allows for faster temperature adjustments and manipulation during roasting. “Air roasters respond very quickly when adjusting temperature, explains Emilio, who works with a 15kg fluid bed roaster. “Plus, you notice changes in the profile almost immediately. The downside is that you can instantly ruin a batch if you get distracted. Or simply get a different roasting profile than planned.”

While Ken agrees, he touches on a few different points. “Fluid bed roasters do a good job of bringing the bean temperature up smoothly and consistently. The shorter roast times also allow you to achieve darker roasts in a shorter amount of time, keeping the sugars and oils inside the bean where it belongs.”

Roast speed and control

As the beans constantly move in an air roaster, more heat is transferred in a shorter time, resulting in a faster roast. Emilio claims this is one of its main advantages. “Air roasters have an expeditious way to operate. They’re very fast, and you can finish roasting in about 3 minutes.”

He stresses that as they work faster, you as the roaster must be extremely focused. “You can perceive physical and aromatic properties changing and adjust gas pressure quickly. It’s more subtle with air roasting, but you have control.”

Roast profiles

Roasting on a fluid bed tends to highlight the acidity of coffee beans more than drum roasting. The result is a more acid and fruity profile. Drum coffee roasting allows for more precise temperature control than fluid bed roasting and can produce a darker roast with more body and sweetness.

“I haven’t struggled with roasting problems with air roasters, such as baked coffee beans, scorching, tipping, or any other roast defects. It just takes special care, like any method,” Emilio says. 

Ken adds that fluid bed roasters also do an excellent job of removing chaff from the roast chamber before it reaches the stage of burning. This protects the beans from taking on the bitter flavour.

Cost

Overall, fluid bed roasters are less expensive than drum roasters. “Roasters save energy and money, as they don’t need gas to preheat the roaster,” Emilio explains. 

“One of the main benefits we see in fluid bed roasting is the initial startup cost,” Ken agrees. “Most fluid bed roasters are less expensive to manufacture and more cost-effective to maintain. This is because most fluid bed roasters have one moving part: the bean loft motor.”

Furthermore, Ken explains air roasters are easier to operate, which makes training staff less complicated. 

An image of a coffee roaster weighing roasted coffee for packaging, sustainable coffee packaging, sustainable coffee bags, PLA coffee bags, LDPE coffee bags, in an article on fluid bed roasters

Are fluid bed roasters a more sustainable option?

“Another benefit that is becoming more important is the environmental impact,” Ken says. “Electric fluid bed roasters take much less energy per pound to roast.” He explains the fluid bed roasters at Coffee Crafters take approximately 3200 British Thermal Units (BTU’s) per pound to roast with a 6 to 10-minute roast cycle. “That is less than half the BTU’s per pound of most drum roasters.”

As Emilio does not need to heat his roaster, he saves about two gas loads per roast. “When calculating a full year of roasting, that’s a significant saving,” he says. 

Regarding product fit, finding small and amateur roasters using fluid bed coffee roasters was more common. Now, it has become easier to use air roasting for commercial purposes. Ken explains the brand used to focus on home roasters, but that is shifting. “We have added a focus on coffee shops, bakeries and other food-based businesses. We are also releasing a new medium-size roaster with a 150lbs per pound capacity so our customers can enter the wholesale market.”

Those entering the wholesale coffee market must ensure their coffee is packaged correctly so customers can enjoy a quality product. At MTPak Coffee, we offer our roasters 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.

Our custom coffee mailer boxes are made from recycled cardboard and are strong, durable, and weather resistant. These highly customisable and recyclable coffee boxes can be used for ecommerce sales, coffee subscriptions, blind-tasting boxes, and more.

All of our packaging options are designed to minimise waste and contribute to a circular economy. Plus, we can customise your coffee packaging to your specifications – ensuring your brand stands out. 

We also offer 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 coffee bags, contact our team.

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Yker Valerio
Yker Valerio

Yker is a writer for MTPak Coffee and is very passionate about his craft.

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