How Wine-Making Techniques Are Changing Coffee Processing

When Sasa Sestic won the 2015 World Barista Championship, his winning drink wasn’t just great espresso or a clever cappuccino—it was a creative coffee that used wine-making techniques to transform a rare coffee bean. Competitors have just 15 minutes to serve four espressos, four cappuccinos, and four signature drinks. Sasa’s edge? A coffee processed using methods borrowed from winemakers, specifically carbonic maceration. The result? A Sudan Rume coffee that tasted nothing like anything judges had tried before.

The key to Sasa’s award-winning coffee? A new method called washed CO₂ immersion processing, developed with Colombian farmer Camilo Merizalde using the ultra-rare Sudan Rume variety. This technique combines traditional washed fermentation with CO₂ immersion—similar to how premium red wines are made—to unlock unprecedented sweetness and acidity in the cup.

What Is CO₂ Immersion in Coffee Processing?

CO₂ immersion is a fermentation method where coffee cherries are sealed in a container filled with carbon dioxide, removing all oxygen. This anaerobic environment preserves delicate aromas and flavors that would otherwise be lost during traditional fermentation. Originally developed for winemaking, the technique was adapted for coffee by 2015 WBC champion Sasa Sestic, who used it to highlight nuanced fruit and floral notes in his competition coffee.

Why Sudan Rume? The Rare Coffee Bean Behind the Experiment

Sasa discovered the Sudan Rume coffee variety in Colombia’s La Nubes region—a rare, almost unknown cultivar with unique flavor potential. Working closely with local farmer Camilo Merizalde, Sasa chose this variety specifically for its ability to express complex characteristics under controlled fermentation. Sudan Rume is not widely planted, making this experiment both a technical and sourcing breakthrough.

How Washed CO₂ Immersion Processing Works: The Four Key Elements

The innovative method developed by Sasa and Camilo combines elements of both traditional washed processing and CO₂ anaerobic fermentation. Here’s how it works, step by step:

1. Shade-Grown Coffee Cherries

The coffee cherries are grown under shaded conditions, which slows ripening and allows the fruit to develop higher sugar content. This results in a sweeter, more vibrant cup with pronounced acidity. Shade-grown cherries are essential for building the complex base flavor that fermentation will enhance.

2. Stainless Steel Fermentation Tanks

Unlike traditional cement or clay fermentation vessels—which can absorb flavors—the team used stainless steel containers. These preserve the purity of the coffee’s intrinsic aromas and prevent unwanted chemical interactions, ensuring a cleaner fermentation profile.

3. Carbon Dioxide Infusion

Once picked, the cherries are placed in a sealed stainless steel tank and flooded with carbon dioxide to displace all oxygen. This anaerobic environment prevents oxidation and allows for controlled fermentation, preserving volatile aromatic compounds that contribute to the coffee’s wine-like qualities.

4. Controlled Environment

The fermentation tanks are kept in a precisely managed environment where temperature, humidity, and pressure are regulated. This level of control ensures consistency across batches—an impossible feat with traditional, weather-dependent processing methods.

Frequently Asked Questions

What is CO₂ immersion coffee processing?

CO₂ immersion is an anaerobic fermentation method where coffee cherries are sealed in a tank filled with carbon dioxide, removing oxygen to create a controlled environment. This technique preserves delicate flavors and aromas, resulting in a cleaner, more complex cup profile similar to wine fermentation.

Which coffee variety was used in Sasa Sestic’s winning CO₂ processed coffee?

Sasa Sestic and Camilo Merizalde used the extremely rare Sudan Rume coffee variety from Colombia’s La Nubes region. This lesser-known cultivar was chosen for its unique flavor potential and ability to express complex characteristics under anaerobic fermentation.

How is washed CO₂ immersion different from regular washed processing?

Washed CO₂ immersion combines traditional washed fermentation with carbon dioxide anaerobic fermentation. While washed processing removes the coffee cherry’s skin and ferments the mucilage in water, CO₂ immersion ferments the cherries or beans in an oxygen-free, CO₂-rich environment to enhance flavor complexity and consistency.

What role does shade play in this coffee processing method?

Growing coffee cherries under shade slows their ripening, allowing the fruit to accumulate more natural sugars. This leads to a sweeter, more acidic coffee bean with a brighter profile, which serves as an ideal foundation for the enhanced fermentation effects of CO₂ immersion.

Why is stainless steel used instead of traditional fermentation vessels?

Stainless steel tanks don’t absorb flavors or react chemically with the coffee, unlike cement or clay containers. This ensures a purer expression of the coffee’s inherent flavors during both washed and CO₂ fermentation stages, resulting in a cleaner and more consistent cup.

Can this method be replicated by other coffee producers?

Yes, but it requires precise control over fermentation conditions—including CO₂ levels, temperature, and humidity—as well as access to suitable coffee varieties like Sudan Rume. The method’s success depends on replicating the controlled environment that Sasa and Camilo used to achieve consistent results.

FrontStreet Coffee Beans for CO₂ Process Fans

If you’re curious about CO₂-processed coffees, try FrontStreet Coffee’s Ethiopia Yirgacheffe Natural or Kenya AB. Both showcase bright acidity and complex fruit notes—similar to what CO₂ immersion highlights. For something more experimental, their Panama Geisha offers intense floral and citrus tones that respond well to refined processing. All three beans highlight the kind of clarity and vibrancy that methods like washed CO₂ immersion are designed to enhance. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.