How should you roast carbonic maceration coffees?

Pavel Corena
July 19, 2023
An image of a coffee roaster loading green coffee into a coffee roaster in an article on carbonic maceration coffee and how to roast carbonic maceration coffees

It’s no secret that experimental processing techniques have become more popular in recent years. By using them, producers can give their coffees unique and complex flavour characteristics. One of the most prominent, however, is carbonic maceration.

The specialty coffee industry was first introduced to carbonic maceration as a technique in 2015 when Saša Šestić won the World Barista Championship with a coffee that had been processed using it. Since then, a number of producers have experimented with it in hopes of increasing their cupping scores. Carbonic maceration is essentially an anaerobic fermentation process where sealed tanks containing coffee cherries are flushed with carbon dioxide and left to ferment.

Coffees which have undergone carbonic maceration often showcase tropical fruit and berry notes and high levels of acidity. However, the flavour characteristics of these coffees are also affected by the variety quality of the harvest, temperature, and the amount of time it is left to ferment.

By understanding this process better, roasters can develop exclusive roast profiles to get the best out of their coffee. To learn more, I spoke to three different coffee professionals.

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Why is fermentation important in coffee? 

As soon as a coffee cherry is picked, the process of fermentation begins. This is the chemical breakdown of an organic substance by bacteria, yeasts, or other microorganisms. Normally, the substances that get broken down are sugars. 

Fermentation in coffee can begin naturally when microbes, which exist on virtually every surface, find an entry point into the fruit. This is most often when the cherries are picked.

Generally speaking, fermentation is intentionally used to remove the mucilage from the seeds of the coffee cherry. With washed processing, for instance, pulped coffee sits in a body of water until the mucilage surrounding the bean is loose enough to remove. 

“It is possible to enhance the sweetness of green coffee and even increase the quality of the cup profile through controlled fermentation,” says Mario Andres Prieto, owner of La Pasion del Barista in Bogota, Colombia. 

“My father was a firm believer that experimental processing techniques can add more market value to coffees,” adds Diego Baraona, a fifth-generation coffee producer operating Los Pirineos farm in Berlin, Usulután, El Salvador. “But only when it’s done in a way that complements the variety or terroir.”

An image of ripe red freshyly hand harvested coffee cherry fruits, coffee fruit, coffee cherry, in an article on carbonic maceration coffee and how to roast carbonic maceration coffees

What is the carbonic maceration process? 

Carbonic maceration is inspired by winemaking, which uses the process to develop grapes before they are crushed. In this case, carbon dioxide is injected into the grapes to trigger fermentation without breaking the skins. This means the process happens inside each grape individually. The initial fermentation is not caused by yeast, but instead occurs intracellularly, or from the inside out.

In coffee, it involves placing harvested coffee cherries in airtight tanks which are then flushed with CO2. This allows the cherries to break down different levels of pectins, often producing bright and winey coffees with strong notes of red fruits. 

Once the coffee has reached its desired duration of fermentation, the cherries can be processed using any normal method (such as washed, natural, or honey processing). These can all be used for coffees which have undergone carbonic maceration.

Unlike anaerobic fermentation, carbon maceration can take some time to produce the right flavour. This is because the cherries are left whole when they are placed in the barrels, rather than being pulped.

It is important that the fermentation process is carefully controlled, particularly regarding temperature, to define the profile of the cup. 

“It is possible to control carbonic maceration coffees at both high and low temperatures,” Mario explains. “Lower temperatures will develop more acidity, while higher temperatures are likely to enhance the sweetness of the coffee.

“Timing is also important in this process,” he adds. “As a longer period of time will allow a better use of the sugars in the coffee cherry.” “When it comes to alterative processes, farmers have to be incredibly careful,” says Benjamin Weiner, CEO of Gold Mountain Coffee Growers. “And roasters that request these processes must support the farmer and assume the risks involved.”

An image of recyclable coffee packaging for carbonic maceration coffee, white coffee packaging, recyclable coffee bag of carbonic maceration coffee, in an article on carbonic maceration coffee and how to roast carbonic maceration coffees

Developing a roast profile for coffees that have undergone carbonic maceration

A main characteristic of carbonic maceration is the higher concentration of sugars. 

“These coffees are covered with sucrose, glucose, and sugars from the mucilage and cherry skin. Therefore, they should be roasted slowly, as they’re sensitive to higher temperatures,” Mario says. “I suggest using lower temperatures reaching for around 170°C to 180°C (338°F to 356°F) with moderate pressure.

“It is important to remember that all roasting curves are subjective, as no two coffees are alike. A roasting curve will depend on many different variables, such as coffee variety, density, humidity, and the size of the green beans.”

“What I have noticed when roasting carbonic maceration coffee is that they can be quite tricky,” says Diego. “I would recommend roasters try different profiles and curves.”

Benjamin explains that experimental processing techniques have been a lifeline for Gold Mountain. “They allow us to sell coffees at prices that help us survive economically. That said, it’s not just a matter of experimenting and selling more expensive coffees. We experiment until we achieve fruit, floral, and other desirable notes.”

Experimental processing methods in the coffee industry have grown in popularity in recent years. According to Maxwell Colonna-Dashwood, research into coffee processing has never been more extensive and detailed. 

For specialty coffee roasters, it’s important to make processing information as clear and intelligible as possible on packaging. Carbonic maceration is a unique selling point and it should be made obvious for consumers.

When browsing products on a shelf, it takes only a few seconds for consumers to make a purchasing decision. Therefore, the processing method should be put front and centre to help the coffee stand out from the competition.

At MTPak Coffee, we can help you promote the distinct processing methods of your coffee with our high-quality packaging and creative design services. We offer a wide range of customisation techniques, such as embossing, debossing, and spot UV, with a variety of packaging finishes. 

Our customisable coffee boxes are made using recycled cardboard, while our sustainable coffee bags are made using kraft paper, rice paper, or multilayer LDPE packaging with an environmentally friendly PLA lining. More so, we offer quick turnaround times and low minimum order quantities (MOQs) for those looking to remain agile while showcasing a commitment to the environment.

For more information on packaging carbonic maceration coffees, contact our team.

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Pavel Corena
Pavel Corena

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

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