What is Yeast Fermentation Processing? The Origin of Yeast Fermentation and Panama's Emerald Manor Geisha

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FrontStreet Coffee's Overview of Yeast Fermentation Processing

Yeast Fermentation

The yeast fermentation processing method draws inspiration from the wine industry. Today, through continuous experimentation, coffee farmers add yeast and bacteria during the fermentation process to better control the effects of fermentation.

Yeast and bacteria are very important elements in the fermentation process. In the natural fermentation of coffee, different microorganisms participate in the fermentation process. Enzymes produced by yeast and bacteria will break down the sugars in the mucilage.

Yeast commonly appears in bread making, wine brewing, cocoa bean processing, and the treatment of green coffee beans.

Wine brewing primarily uses commercial yeast fermentation. Yeast fermentation controls the microorganisms during the coffee fermentation process, changing the coffee's flavor to make it less bitter and less astringent, sometimes even less acidic. The method involves selecting specific yeast or microorganisms for what is called secondary fermentation.

Yeast fermentation originated from Gothenburg, Sweden. French biology PhD Camille Delebeque gave a presentation at Re;co. His company, by controlling microorganisms during the coffee fermentation process, changes the coffee's flavor to make it less bitter and less astringent, sometimes even less acidic. He calls this product "Cultured coffee" or "microbial coffee."

Their method involves selecting specific yeast or microorganisms for what is called secondary fermentation, enhancing good flavors or reducing undesirable ones. Although he didn't reveal what microorganisms he uses, nor explain how his secondary fermentation is conducted, and provided no information about coffee origins or bean varieties, his product pricing is by no means cheap - 5 ounces (148g) costs $29.

El Salvador's most renowned coffee farmer, Aida Batlle, collaborated with American roaster Equator to test the impact on flavor by adding yeast to fermentation tanks for Bourbon from the Buenos Aires farm in El Salvador, comparing it with traditional washed processing without yeast. In 2017, they experimented with two different yeasts and found that different yeasts produced different results. One increased the coffee's sweetness, balance, and consistency, while another enhanced brightness and fruit notes. The yeast processing added flavors that are difficult to obtain with traditional washed processing: sugarcane, lemon, nutmeg, and sage.

Panama Geisha Auction Yeast Processing Series

According to official disclosed information, this ES-Y series consists of four LOT batches and nine boxes of beans, using a brand new processing method "yeast fermentation" that produces uniquely flavored Geisha.

One of the biggest highlights of this year's auction is the addition of "yeast processing batches": special yeast is added to the fermentation tanks for 48 hours of fermentation before washing, then dried on drying beds for 4 days. This unique yeast processing batch. Adding yeast during the post-processing makes the fermentation process faster and more thorough, producing special flavors.

Depending on the yeast, the red wine flavors vary. Compared to yeast B, yeast A has more obvious red wine flavors, while yeast A's red wine flavors are more delicate, presenting Geisha's characteristics more beautifully, which is why Y-1 is priced higher.

Lot ES-Y-1: Processing method: Added yeast A for 48 hours of fermentation, then washed, followed by 4 days of drying on racks, auction price: $340/pound!

Lot ES-Y-2: Processing method: Added yeast B for 48 hours of fermentation, then washed, followed by 4 days of drying on racks, auction price: $111/pound!

According to estate manager Rachel Peterson, this "yeast fermentation method" is an experiment by Hacienda La Esmeralda in processing methods, used to observe how Geisha coffee performs after yeast inoculation fermentation.

Processing method: Fully mature bright red fruits are hand-picked, filtered for undersized and water-floated selection, then soaked in clean water. Fermentation time is approximately 48 hours with yeast added, followed by sun drying. Spread on drying beds at approximately 1-2 layers thickness, undergoing 4 days of sun exposure. Average temperature: daytime: 16°C - 23°C, nighttime: 10°C - 15°C, completing completely different unique flavors!

After our cupping of the yeast-processed red label, we were delighted to find that this method enhanced Geisha coffee's performance in all aspects (including aroma, body, acidity, and aftertaste), and it's very different from natural processed Geisha. Overall, it's closer to anaerobic fermentation. This processing method's Geisha is excellent in aroma and flavor aspects; it removes the harshness and excessive acidity of washed coffee, bringing balance and rich layers, while adding red wine-like flavors.

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