Experimental Coffee Processing Methods, Explained

Experimental Coffee Processing Methods, Explained

If you've ordered coffee from us before, you're probably somewhat familiar with terms like "washed," "honey process," and "natural"—different methods of converting coffee cherries into dry green beans that are shipped to us ready to roast. (If these terms are new to you, head over to former green coffee buyer Chuck Patton's blog post on the basics of coffee processing.)

Beyond these common processing methods lies a world of possibility for coffee producers. Experimenting with different soaking periods, wash frequencies, drying environments, and other variables—even controlled bacteria growth—can profoundly affect the flavors present in a coffee and create new experiences for the coffee drinker. 

Since we've been offering a number of uniquely-processed coffees recently, we thought we'd demystify some of the strange terminology involved for you:

Finca Villa Loyola's Carbonic Maceration Process: Developed in the Beaujolais region of France in the 1930s as a wine-making technique, carbonic maceration is a fermentation method that intensifies fruity aromatics while restraining acidity and astringency.

To apply this technique to coffee processing, coffee cherries are rinsed, separated by density, and placed in plastic containers. The containers are then purged using carbon dioxide to expel oxygen and other atmospheric gases. Once purged, the containers are sealed using lids with a one-way valve, allowing gas to escape during fermentation while preventing any from entering. In this CO2-rich environment, fermentation begins intracellularly by the action of enzymes, rather than yeast or other microbes. The cherries are allowed to ferment this way for 72 hours before being moved to shade-covered drying beds where they are dried as a natural-process coffee. Our first offering of this coffee received 93 Points from Coffee Review!

La Palma y El Tucán's Lactic Process: Direct Trade partners La Palma y El Tucán have achieved excellent results by putting bacteria to work, emphasizing fruit notes and adding complexity to various microlots from their own farm and others in their Neighbors & Crops program. Doña Rosalbina Lactic Process was our latest offering from them. Lactic fermentation allows for the growth of lactic acid bacteria under anaerobic conditions with constant measurement of oxygen level, sugar content, and pH. The bacteria feed on sugar present in the mucilage, generating a high concentration of lactic acid. After reaching the desired pH, the coffee is soaked in clean water to stop the growth of bacteria and dried on raised beds. (You may have tried our Blanca Cano Lactic Honey Process, pictured at top, or our Lot No. 36 Lactic Gesha earlier this year.)

Finca Kilimanjaro's Experimental Processes: Aida Batlle of Finca Kilimanjaro is regularly praised for her high-quality coffee and unique experiments with fermentation. Different fermentation styles highlight different qualities in coffee: dry fermentation amplifies sweet, chocolate, and fruit notes, while wet fermentation produces a soft body and complex acidity. With either method, strict control is necessary to prevent any off flavors from developing.

Last year we offered two styles of washed coffees from Aida—Burundi Process and Ethiopia Process—along with her Natural Process. More recently we offered a more radical experiment: Cascara Fermentation. For this nanolot, Aida’s team brews a batch of cascara tisane (a tea-like brew made from dried coffee cherry skins), strains it, and allows it to cool. Once the coffee is depulped, it’s placed in a fermentation tank with the cascara tea to ferment for 12 hours. The coffee is then dried on raised beds. Our roast in early 2017 received 95 points from Coffee Review! 

PT's Haraaz Special Red drying on raised bedsHaraaz Special Preparation (above): Our recent Blue Label offering from Yemen broke with tradition. Yemeni coffee has a reputation for being very earthy, with deep, muddled fruit notes, because it is usually harvested after drying on the tree and then dried further on rooftops after harvest. Instead, this selection consisted of cherries picked ripe and then dried on raised beds for improved air circulation, which results in a cleaner, juicier, yet still very rich cup. (This is akin to East African naturals, which are dried on raised beds.)

Mountain Water Process Decaf: The Mountain Water Process involves soaking green coffee in fresh mountain glacier water until it reaches a saturation level that allows the dissolvable solids, including caffeine, to be extracted. The water then passes through carbon filters, removing the caffeine before being returned to the tank. Under pressure, coffee oils are reintroduced to the green coffee, leaving it around 98% caffeine-free.

Finca Las Mercedes La Avila Double-SoakFinca Las Mercedes' Double-Soak Method (above): Lucia Ortiz of Finca Las Mercedes first tried this experiment in 2012... and the resulting coffee won El Salvador Coffee of the Year! Within hours of harvest, coffee cherries are depulped at the farm's mill. The coffee is left in a fermentation tank where enzymes break down the remaining sweet mucilage. After fermenting for 12 to 18 hours, the coffee is sent through washing channels to completely clean it. Up to this point, the process is identical to a washed coffee. The difference comes in the next step: the coffee is moved into a special tank to soak for an additional 24 hours. The tank is then emptied and the process is repeated, filling the tank again and letting the coffee rest for 18-24 additional hours. After the second soak, the coffee is dried on patios before being packaged and shipped to us.

Duncan Estate's Wine Process: The Koyner/Duncan family migrated from Canada to Panama in the late 19th century, and more recently transplanted an idea from wine production to coffee production. Their Wine Process involves leaving the coffee cherries on the shrub for two weeks after maturity, allowing the fruit to over-ripen. Once the coffee fruit is harvested, it is sun-dried for several days in a cool climate at more than 5,500 feet above sea level. The result is a uniquely strong, fruity and fermented, wine-like cup profile.


Each of these processing methods allows the producer to leave more of a mark on the coffee he or she has grown, and in some cases these experiments have led to international recognition in the specialty coffee world. 

Next time you're looking for a new coffee experience, try a new process!

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