Fun With Ferment: Anaerobically Processed Coffees

In early April, some rather odd-smelling packages began arriving at the Coffee Review lab. Describing the collective aromas that wafted from them is difficult. And describing those aromas continued to be difficult once we started actually tasting the coffees inside the packages. Certainly, there was lots of fruit and chocolate. And fragrant cut cedar, and sweet flowers. But along with these more familiar coffee aromas came some that we do not usually associate with coffee. Maybe soft cheeses, like the mild goat cheese one eats in salads. Or, occasionally, more pungent cheeses like feta or blue cheese. Sometimes kefir, that gentle, tangy-creamy liquid version of yogurt. Sometimes fresh earth, tobacco or mushrooms. And occasionally, notes that we may not associate with food at all. Musk, for example, the deep, pungent, often perspiration-like aromas used as base notes in perfumes, originally derived from secretions of the male musk deer.

These packages contained coffees that were processed using techniques the coffee world has come to call “anaerobic.” Very broadly, this term means that at some point the coffees were subject to fermentation while shut inside sealed bags or tanks with limited access to oxygen.

Most of us are familiar with the sensory character of coffees that have been fermented with access to oxygen. We recognize the sweet, fruit-forward notes produced by oxygen-loving, alcohol-generating yeasts, particularly as we enjoy them in fine dried-in-the-fruit, natural-processed coffees: berries, chocolate, lush flowers, suggestions of wine or spirits.

On the other hand, when fruit is largely deprived of oxygen during fermentation, as happened with this month’s coffees, yeasts are suppressed and various bacteria become more active in fermentation. Rather than the fruit or alcohol-related notes produced by yeasts, these bacteria tend to generate the tangy lactic acid notes we find in yogurt and cheeses, in some sour beers, and in fermented vegetable preparations like sauerkraut or kimchee.

Description Difficult, Pleasure High

Fortunately, we did not have any sauerkraut- or kimchee-nuanced samples among the 43 coffees we tested for this report. Nevertheless, we did struggle a bit in describing and evaluating these anaerobic samples. Many of them almost violently violated the familiar rules defining taints and defects that for years have enabled us to comfortably evaluate classic washed coffees. We found that we needed to examine these coffees from a fresh perspective, starting from the great traditions of fine coffee but not stopping there. We avoided asking ourselves, “is this a fine coffee in the way we already understand coffee?” Rather, we asked ourselves: “Is this an exciting and inherently pleasing variation on the sensory possibilities of coffee?” In particular, we looked for ways that the subtle-to-striking sensory intrigue that anaerobic fermentation brings to the cup expanded on more familiar coffee pleasures.

Coffee cherries processed by carbonic maceration at Finca Villa Loyola in Colombia’s Nariño growing region. Courtesy of PT’s Coffee.

And although we often puzzled about how to understand and characterize these coffees, overall we ended up liking a lot of them. Of the 43 samples we cupped, a very impressive 19 (44%) came off the table at 93 or higher. We’ve chosen 12 of those 19 to review here. All five samples that rated 94 or higher are included. From the additional 14 that rated 93, we selected seven to review based on a range of method, origin and profile.

Anaerobic Definitions

Again, what makes the coffees we tested “anaerobic” by current coffee terminology is that, soon after picking, they were shut inside sealed tanks or bags, protected from access to oxygen-bearing air. The CO2 produced by the fermenting fruit builds up inside the bag or tank, further limiting access to oxygen. Valves allow surplus CO2 to escape while preventing air from entering. The coffee remains sealed this way, largely oxygen-deprived, for anywhere from around one day to six days, after which it is dried. (Predictably, the longer in the bags or tanks, the more pronounced the anaerobic impact.)

Coffees processed by the ASD (anaerobic slow dry) method drying on raised beds in Panama. Courtesy of Geisha Coffee Roasters.

If the seeds or beans remain enveloped by fruit throughout fermenting and drying, the coffee becomes an anaerobic natural. If the drying is deliberately slowed down to 60 or more days the coffee may be further labeled an anaerobic slow-dry (ASD) natural. Finally, if the tanks in which the fruit is fermented are injected with additional CO2 to further cut off the fermenting beans’ access to oxygen, the method may be called carbonic maceration (carbonic refers to the use of CO2; maceration is a rough synonym for fermentation).

So: sealed in bags and dried in the whole fruit for a normal period, anaerobic natural. The same but with deliberately prolonged drying, ASD natural. CO2 injected into the ferment tanks: carbonic maceration natural.

However, we face yet one more layer of terminology. The preceding methods all involve keeping the coffee beans encased in the fruit all the way from fermentation through drying, making them anaerobic variations on the natural method. Other coffees we tested for this report were anaerobic washed coffees: The skin and fruit flesh were removed from the beans immediately after an initial anaerobic fermentation, but before they were dried. These samples understandably tended to be a bit leaner in body but brighter in structure than the anaerobic naturals, yet still quite uniquely composed. Still other samples had only the skins removed after fermentation and were dried with the fruit flesh or mucilage still adhering to them, making them anaerobic honey-processed coffees.

Lots of Surprises, No Neat Distinctions

Returning to the broad picture, a lot goes on inside those sealed tanks or bags during the time the coffee fruit is sequestered in them. Wilford Lamastus of Panama’s Elida Estate, who more than anyone else popularized the slow-dry version of the anaerobic method, points out that during fermentation inside the tank, “There is a significant amount of concentrated liquid from the coffee fruit. This leach is full of the flavors of the variety, the terroir where the plants are located, of natural yeasts, natural microorganisms, natural bacterias …”

Father and son: Wilford Lamastus and Wilford Lamastus, Jr. of Panama’s Elida Estate. Courtesy of Willoughby’s Coffee & Tea.

Note that Lamastus mentions both bacterias and yeasts. From this exercise, I think I can observe with confidence that the neat conceptual separation between fruit-forward coffees subject to yeast fermentation and those subject to tangy bacteria-lactic fermentation is seldom clear-cut in the actual context of the cup. Almost all of the 43 coffees we tested showed clear anaerobically driven characteristics ranging from full-on tangy lactic acid notes to subtle lactic innuendos, but these unorthodox tendencies always overlaid more familiar coffee styles and satisfactions. In naturals, the lush fruit-forward tendencies we associate with alcohol ferment were fused with lactic influences. And in coffees processed with a washed step before drying, the predictably brighter acidity and subtler fruit was deepened by various pungent, tangy-lactic inclinations.

Drying coffee on raised beds at the Ana Sora Washing Station in Ethiopia. Courtesy of Paradise Roasters.

What virtually all of the samples seemed to present is greater-than-usual intensity of sensation, an inclination toward fuller mouthfeel, and often increased sweetness. Roasters who responded to our questions about anaerobically processed coffees often used the term “intensity” when describing them. Most of these correspondents found the intensity valuable, though many cautioned that, given how powerfully anaerobic processing impacts the cup, the method should be applied with tact. A good number apparently would agree with Barry Levine’s (of Willoughby’s Coffee & Tea) observation that “Too much intensity can mask a coffee’s inherent qualities like a dark roast would, although in a completely different way.”

Different in Different Ways

Certainly, one of the most striking overall characteristics of all of this month’s anaerobic coffees is how they express their differences with often disconcerting variety and originality. Here are the 12 samples we review this month very briefly characterized in terms of the singularly successful way each embodies some of the diverse possibilities of the anaerobic approach.

Corvus Coffee Roasters La Estrella Carbonic Geisha Reserve (Colombia; 95). Here the great floral Geisha variety was fermented in sealed, pressurized CO2 and dried in the whole fruit. The result: bright yet lushly layered, complex — overlaid with a very subtle funky intrigue.

Coffee Please Ethiopia Guji Wush Wush Anaerobic Natural (95). Anaerobic natural processing applied to the Ethiopian Wush Wush variety and its classic southern Ethiopia style. Delicate, silky, intricate, with a bonus yogurty, lactic tang.

Paradise Roasters Ethiopia Guji Wush Wush (95). Another Wush Wush prepared with anaerobic natural processing: silky, juicy, extravagantly floral, here with a savory edge deepening the lactic inclination.

Bird Rock Coffee Roasters Tres Dragones Colombia (94). Not an anaerobic natural, as we learned after testing, but a hybrid natural — the whole fruit was subject to fermentation in a covered but not sealed vessel before drying. Consequently, it’s the only sample in this month’s report with a distinct alcohol edge. We called it rum barrel. Add to that mango, chocolate and musk.

Willoughby’s Panama Elida Estate Catuaí Natural ASD (94). Six days sealed in bags and 60 days on the drying patio nets lots of chocolate, massive mouthfeel and deep, lactic-tart acidity with a gently pungent dairy note we called fresh goat cheese.

Geisha Coffee Roaster Elida Natural ASD (Panama; 93). See above. The cheese note struck us as a little sharper here, but pleasingly so, the chocolate just as big, the flowers deep and sweet. And check out the price.

De Clieu Ethiopia Guji Natural Anaerobic Wush Wush G1 (93). Another anaerobic natural Wush Wush from Ethiopia, but this one leans toward the cedary, musky and savory, though with an abundance of crisp chocolate and sweet flowers as well.

Fumi Coffee Peru Yanesha Geisha Double-Anaerobic (93). Two stages of anaerobic ferment before the last of the fruit residue is washed off and the beans are dried makes this a particularly complex version of the anaerobic washed style. Cleanly expressed complexity with the anaerobic contribution resonantly present rather than explicit. Produced from the great Geisha variety as grown in Peru.

Ilustre Specialty Coffee Pink Bourbon Natural Anaerobic Colombia (93). An anaerobic natural that achieves a very light-footed and tropical feel (lychee, jasmine, sandalwood), probably due in part to the typical juicy sweetness of the local Colombia Pink Bourbon variety, in part perhaps to a particularly discreet application of the anaerobic natural protocol. This Ilustre sample is particularly noteworthy for us because it appears to be the first ever sample Coffee Review has reviewed from a Mexico-based roaster.

Nine Point Coffee Ethiopia Oromia Anaerobic Natural (93). Not a dark roast, more a dark-medium, but the pungently sweet, faintly smoky character imparted by the roast nicely complements the Ethiopia fruit (turned raisiny here) and spicy flowers.

PT’s Coffee Roasting Villa Loyola Carbonic Maceration Colombia (93). The plain, straightforward hybrid Colombia variety gets a gentle anaerobic natural boost here, developing quiet chocolate, citrus and flowers, with only a soft hint of fruity funk.

Steady State Roasting Castillo El Paraiso Colombia (93). A classic, powerful Colombia high-grown coffee, washed but with an anaerobic ferment phase added early on that perhaps is what pushes the fruit in a tart, pungent tropical direction: for us, passionfruit and mango.

As producers continue to experiment with the details of anaerobic fermentation, we will undoubtedly see still more variations on the method and still more names for those variations. Open your mind, freshen your palate, and get out your notebook.

And Thanks To

Those roaster contributors whose generous and perceptive comments enriched our understanding of anaerobic processes and this month’s coffees: Rudy Altamirano of Ilustre Specialty Coffee; Yu-lin Chiu of Nine Point Coffee; Phil Goodlaxson of Corvus Coffee Roasters; Patrick Lamastus of Geisha Coffee Roaster; Barry Levine of Willoughby’s Coffee & Tea; Mike Mazulo of PT’s Coffee Roasting Co.; Miguel Meza of Paradise Roasters; Elliot Reinecke of Steady State Roasting; and Maritza Taylor of Bird Rock Coffee Roasters.

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