November 20, 2017

What Roasters Need to Know About Decaf Coffee


Roasters, don’t make the mistake of thinking you can use the same roast profile for decaf and regular coffee. Decaffeination affects the composition of your beans – and in turn, this affects how heat is transferred along the beans’ cells. If you want to get the best out of your decaf beans, and really allow their origin to shine through, you’re going to have to create a unique roast profile.

So how should you adapt your roast profiles for a great-tasting decaf coffee? Aaron Braun, Coffee Quality Specialist at Swiss Water Decaffeinated Coffee Company, agreed to share his advice with me. Here’s what I learned.

Spanish Version: Tostadores: Lo Que Deben Saber Sobre el Café Descafeinado

swiss water decaf process

Green coffee beans on their way to be decaffeinated. Credit: Swiss Water Decaffeinated Coffee Company

Decaf Coffee: How Different Is It?

Aaron explains that the aim of the Swiss Water Process is to remove just the caffeine from the beans – without adding any specific processing taste. However, even just removing the caffeine will affect the structure of the beans. Let’s take a look at those differences.

The first thing you should be aware of is the colour difference. The decaffeination process will alter the appearance of the coffee; in the case of Swiss Water, the beans will be uniform in colour but a few shades darker than regular green coffee. “That exterior visual appearance needs to be taken into consideration,” Aaron emphasises. “Coffee might look visibly more developed than it actually is, so you need to pay special attention to the temperature of the roast.”

Another important point is the bean’s weight: decaffeinated coffee is lighter and less dense because the caffeine compounds have been removed. In turn, this affects how the coffee responds to heat.

SEE ALSO: Roaster Basics: How to Roast Hard & Soft Beans

That being said, decaf coffee is still coffee. Say you have a decaf Ethiopian Yirgacheffe: the biggest determiners of the roast profile are still going to be that origin, the altitude, the flavour profile, the variety, and so on.

What we’re about to suggest is just a few tweaks to your roasting process – the kind of tweaks that will make sure you really do get the best out of those exquisite green beans.

swiss water decaf processed beans

Decaffeinated beans are slightly darker than regular beans. Credit: Swiss Water Decaffeinated Coffee Company

Charge Temperature

Roasting always comes down to heat. And with decaf, you want to be that little bit gentler with it. Keep the charge temperature – the heat of your drum just before you add the coffee – lower. Your decaf beans have less weight and their cell structure has been slightly degraded. This means you want to avoid heating them too quickly.

SEE ALSO: Millennials Turn to Decaf: What Does This Mean for Café Owners?

Aaron wouldn’t give me a guide to the exact temperature (after all, no two coffees are the same). However, he tells me that when they sample roast their decaffeinated coffees at the Swiss Water facilities, they use a charge temperature of 375–400ºF/190.5–204.5ºC.

swiss water

Roasted beans ready for analysis. Credit: Swiss Water Decaffeinated Coffee Company

First & Second Crack

Be careful not to roast your coffee for too long, or too short, a time. First crack should occur at roughly the same time for both decaf and regular beans. However, the roast is likely to progress faster after first crack when it’s decaf in the drum. This is because of the degraded cells and lighter weight. You might be surprised by how quickly second crack comes around.

On the other hand, remember that the beans will be darker than regular ones. Don’t let that fool you into stopping early. Roasting decaf coffees is a delicate balance: you need to pay attention to the development of those delicious coffee aromas, your drum temperature, and more.

Regular and decaf roasted beans

Regular and decaffeinated beans from the same coffee, ready for testing. Credit: Swiss Water Decaffeinated Coffee Company

Final Quality Control

Just like with regular coffee, you’ll want to cup your beans after roasting them. But Aaron also recommends paying close attention to the ground colour consistency. Since the bean surface colour is darker, it’s even more important to check the internal colour.

Not sure how dark your coffee should be? There isn’t a “right” answer (after all, roast levels are a matter of preference). However, when sample roasting, the coffee experts at Swiss Water aim for number 63 on the Agtron scale.

swiss water coffee

Checking the colour consistency of ground decaf coffee. Credit: Swiss Water Decaffeinated Coffee Company

There is no one rule for roasting every coffee, Aaron says, and similarly there is no one rule for roasting every decaf coffee. Be a little gentler with the heat and don’t trust the external bean colour – but remember that, ultimately, you’re not just roasting decaf coffee. You’re roasting a Colombian Bourbon-Caturra blend, a Zambia Mafinga Hills, or a Sumatra Mandheling. There is so much more to a coffee than whether or not it has been decaffeinated.

Please note: This article has been sponsored by Swiss Water Decaffeinated Coffee Company.  

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