“Since the rise of the coffee shop, culture has disappeared, don’t you think? People are horrified that they have to pay for music. Music! But $20 for two coffees, oh, absolutely.”
Noel Gallagher (singer, guitarist and frontman of Oasis)
I didn’t plan to end up in coffee.
It’s one of those ice breakers that you can fall back on at any industry gathering, asking what meteor had to strike which road to divert you into the penniless pursuit of caffeinated, brown water—and my journey was no different.
In college, I paid my way through second and third year working off-hours out of the recording studio in my college’s basement, engineering tracks for whatever band needed to get whatever demo together to book a whatever show or tour. I’ve been playing and recording music for most of my life at this point—and back then, I thought music engineering and production would be a good career for me, or at least one that would offer engaging, interesting work.
To this day—many of the ways I talk about coffee on the cupping table are related to that experience in the recording studio (“it’s all trebles and no basses,” or “that one’s got the mids scooped,” or referring to “loudness” of a coffee rather than its intensity).
Back when I was doing audio engineering work, it was the height of what would come to be known as “the Loudness War.” Mainstream acceptance of compact discs and the advent of digital recording technologies led to a certain phenomenon: mastering houses (mostly at the behest of record labels) began producing recordings that had the audio signal compressed: that is to say, the dynamic range was reduced.
[Oasis’ (What’s the Story) Morning Glory? is often credited with firing the first shot of the Loudness War, which also gave us such auditory atrocities as Californication by the Red Hot Chili Peppers and Katy Perry’s Teenage Dream, which is technically—and inexplicably—louder than Megadeth]
Before, you might have a recording of a song where the difference between the loudest note and the lowest note was 20 dB; now, it might be just 2 dB (and keep in mind, the decibel scale is logarithmic). By reducing the difference between the loud and quiet parts, you could increase the gain of the overall signal—making the track louder.
Much louder.
And it turns out that if you were to take a song and play it back at two different volumes (one standard and one just a little louder), humans prefer the louder one—at least in the short term.
Grabbing attention matters for radio and commercial sales, of course, and it matters for selling records. Master the record hot, and it’ll sell—or so the logic goes.
But that loud signal lacks dynamic range and never gives your ears a rest. At first it grabs your attention and sounds really good—but then, your ear gets used to it. It attenuates the sound, and, after a while, grows fatigued. It gets tired. Eventually, we get used to that feeling of having our ears shredded, so anything less than doesn’t seem that exciting anymore. It just sounds…quiet. And thus, we need more signal, more noise, more loudness—just to feel that same excitement again.
The cycle of escalation lives on.
Over a decade later, I’m not doing much audio work anymore and my drums have collected more dust than a chaff barrel. But as I taste through coffees from exporters and high-end specialty roasters around the world, I can’t help but wonder: is the coffee industry currently engaged in its own Loudness War?
Processing—and fermentation specifically—isn’t new to coffee, any more than compression was new to the recording industry. But the way modern processing uses fermentation—to amplify, to make a coffee loud on the cupping table—can make it seem like the fermentation itself is the front man and has greater impact on the final cup than cultivar, climate, or agronomy.
It defines a style in and of itself, and like so-called “brick wall compression” (called that because it takes the signal and jams it against unity as hard as possible—like driving into a brick wall) has as many advocates as it does detractors.
And it’s hard to say that there’s anything objectively wrong with these coffees: much as I might sometimes lament the difficulty of finding clean, washed coffees or complain about anaerobic style coffees that taste like compost bin juice, I also know that these wild, loud flavor profiles are driving a new generation of coffee drinkers to pay attention to where their coffee comes from. In some ways, they’re growing the industry—just like those blueberry-bomb Harrars you can’t get anymore did back in the days of music’s Loudness War.
But looking around, it seems that coffee processes are kind of like days of the week: no matter what we do, a new one just keeps coming.
It’s gotten confusing: for every “washed process” there’s a “bioinnovation” or “molecular process;” for every “natural” there’s a “hydro-natural” or “cryomaceration.” Gone are the days of over-simplified, generic descriptors.
We’re slamming that brick wall—using fermentation in ways it would have been inconceivable in the year that Oasis released (What’s the Story) Morning Glory?
Some argue that streaming and the use of “normalization” technology, which makes every song on your playlist, no matter when or where it was mixed and mastered, play back at the same volume—ended the loudness war. I think that’s where my analogy breaks down—but maybe, if we’re lucky, we’ll find a way to dust off our old LPs and fall in love with the sweet, warm tones of impeccably-processed washed coffees again and keep those in our playlist, too.
I spend a fairly inconceivable amount of time on Instagram these days responding to DMs from people asking me to clarify the differences between X and Y process, or to explain what Z process means, so I thought it might be helpful if I put together a little glossary of some of those processing terms that have made their way into cut sheets that exporters send with green coffee samples and that roasters stamp on their bags—and if I missed any, please feel free to drop them in the comments.
And if you happen to know what coffee started our own Loudness War—I’d love to know that too.
Looking at the list that follows, there are roughly four main levers that a producer can manipulate and which will define the processing style:
- Variations on pulp/skin removal
- Variations on environment
- Various inoculations and additives
- Variations on time/contact
Broadly speaking, coffee processes as they’re labeled and marketed by roasters and producers today tend to speak to the influence or intention of a certain style, or perhaps naming the primary variable a producer manipulated to create that coffee. That is, they tend to speak more specifically to manipulation of one variable and leave assumptions about the others.
All of the processes below have been explored through the lens of these four categories, which all have different impacts on the fermentation kinetics. I’ve also provided a bit of a description in case that’s more helpful.
Luca Costanzo suggested I lay this out in a table to make it a bit easier to understand, and since he’s often right about these things, I have done exactly that.
It’s a bit hard to read the table below—so this is the original spreadsheet, for ease of searching and reference.
| Process | Pulp removal | Environment | Inoculants or additives | Time/contact | General description | Also known as |
|---|---|---|---|---|---|---|
| Wet | Yes, always | Varies | If you want | Not critical to definition/ varies wildly | “Wet process” is a general category that defines all coffee processes in which skin is removed before drying. It doesn’t matter if there is never water used in the process—all we’re talking about is whether the “wet” part of the cherry is exposed during drying. If the skin is removed at any point during processing, it’s a wet process. | |
| Dry aka natural | No, never | Varies | Sometimes | Not critical to definition/ varies wildly | “Dry process” is a general category that defines all coffee processes in which the coffee dries with the skin and pulp still attached. It doesn’t matter if there is water used in the process either for floating or fermentation in cherry—all we’re talking about is whether the coffee dries in cherry. Dry process is the opposite of wet process: if the skin stays on, it’s a dry process. “Natural” process is a synonym for this category, but it most commonly refers to coffees that have not undergone additional fermentation steps and is simply picked (possibly floated) and then dried in cherry. | Natural process |
| Washed | Yes, always | Varies | Si lo quieres | Not critical to definition/ varies wildly | Washed process refers simply to coffee that has had its mucilage removed. This can be done mechanically (in which case, it’s most common for there to be little if any fermentation though it is possible to ferment both before and after mechanical washing and some producers do this) or via a fermentation to break down the pectin in the mucilage to allow the mucilage to be washed away by running water over the coffee. Every other variable in the equation is up for grabs—including fermentation in cherry and pre-ferments (and depending where you are, traditional practices vary wildly), but no matter what: the mucilage will be removed before drying. | Fully washed |
| Pulped natural | Yes, always | Varies | Sometimes | Until dry | This process evolved from the need to produce coffee faster and with lower risk of defects than the dry process method traditionally used in Brazil. The name is what it is: it’s pulped (as in the skin is removed) but then it’s dried like a natural (with the mucilage still attached). This technique also describes honey processing (which comes in white/yellow/red/purple/black variants depending how much mucilage was removed) which is essentially the same thing. Popularized widely by Graciano Cruz in Panama around ~2010, honey processing aims to achieve different sensory profiles based on the amount of mucilage removed and a greater attention to cherry selection, with good honey processes achieving the body and sweetness that traditional coffee buyers would attribute to dry process coffee while also providing acidity and clarity more common to washed coffees. Coffee that was pulped and then fermented can still be described as honey process—as long as it is dried with the mucilage still attached. | Honey |
| Carbonic maceration | No—at least not initially | Carbon-dioxide flushed | Sometimes | Not critical to definition/ varies wildly | Named after the winemaking practice common to the Beaujolais region of France in which whole grapes are fermented prior to crushing, this process was popularized by Saša Šestić during his WBC presentation in 2015. In carbonic maceration, whole coffee cherry is placed into a sealed vessel which is then flushed with carbon dioxide. If I’m being honest, this process not that dissimilar from “Anaerobic processing” in that both are intended to be low-oxygen environments—but in carbonic maceration the fermentation (the initial fermentation, anyway) must always happen in cherry, and carbon dioxide is always added to the environment. | |
| Anaerobic | Sometimes | Low oxygen / closed container | Doesn’t matter/sometimes | Not critical to definition/ varies wildly | This is one of those styles of processing that is all over the place in practice but refers pretty much exclusively only to one variable: the fermentation environment. In most cases, producers will place coffee in a closed container (like a 55 gal drum) with an airlock, the idea being that as the fermentation progresses, oxygen in the tank is displaced by carbon dioxide produced through fermentation. Some producers go further and flush the fermentation environment with an inert gas like nitrogen, or carbon dioxide (see: Carbonic Maceration). The intention of this process is typically to advantage certain obligate anaerobes or facultative anaerobes (including yeasts such as Saccharomyces Cerevisiae or lactic acid bacteria) and disadvantage spoilage organisms like Acetobacter—as well as reducing oxidation. It seems logical enough. But the situation often arises where temperatures aren’t controlled well, or the fermentation progresses slowly and oxidation does occur and acetobacter does emerge as alcohol builds, pH drops, and the dormant bacteria find the oxygen…In reality, it’s extremely difficult to actually purge all free oxygen from the environment even if you flush it with gas. Besides: technically “Anaerobic” is a nonsensical fermentation style, since all fermentation is by definition anaerobic (if you listen to Lucia’s podcast you know all about this by now)—but rather than referring to the fermentation, most producers are referring to the environment, which leads to a different term: the nearer-to-correct “anoxic” (meaning “without oxygen”). The situation gets more confusing when you realize that the “anaerobic” part of the process can happen in cherry, too—which may then be either dried, or pulped for a wet process; or it may occur after pulping as parchment. Without knowing more about what happened during the processing, the term “anaerobic” on its own is rendered unspecific and incomplete to describe a coffee. | Anoxic, hypoxic, sprouting |
| Acetic process | Depends who you ask | Oxygen-rich | Not usually | Not critical to definition/ varies wildly | This is another process that changes depending who you ask—but one thing that will always be true is that it requires an oxygen-rich environment as Acetic Acid Bacteria (AAB) are obligate aerobes (meaning that they require oxygen for their metabolism). Typically, acetic acid in coffee is thought of as a cause of the defect formerly known as “ferment”—which tastes like compost bin juice, overly sour kombucha, salad dressing, or rotting cherry (or to some, inexplicably: vanilla). However, in low concentrations, we perceive acetic acid (which is also generated during roasting) as fruity or floral (in fact, there is research using acetic acid as a way to improve the sensory character of coffee). To La Palma y El Tucán, who popularized the “acetic process” naming convention, this process involves placing pulped coffee in a vessel where it can be mixed continuously during fermentation, exposing the coffee to oxygen and encouraging the growth of aerobic bacteria such as AAB (as well as yeasts like Saccharomyces Cerevisiae, which is most commonly thought of as a facultative anaerobe that is more efficient at replication in aerobic conditions). To other producers, this process means placing whole cherry under water in an open tank, which is mixed periodically again to encourage the growth of AAB. | |
| Kopi Luwak | Yes | I’ll say | No | It takes how long it takes ¯\_(ツ)_/¯ | “Coffee from assholes, for assholes” (thanks, Jason). In this process, a civets cat eats (read: is usually captured, caged and force-fed) coffee. The “Processing” occurs when the seed passes through the digestive tract of the animal, fermenting the pulp and changing the coffee along the way prior to its…..departure…from the animal’s body. Kopi Luwak coffee is weirdly heavy in body, low in acidity, and in so many words tastes like shit. It gives a different meaning to “Tail to snout.” A similar process in Brazil called “Jacu” is named after Jacu (an African Grey Parrot), which eats and gastrointestinally ferments coffee cherry. | related: Jacu |
| Cryomaceration | Yes | Very cold water | Sometimes yeast | Days. Typically 200+ hours, but I’ve seen as many as 700+ (and Ben from Manhattan shared with me a sample of a coffee that was kept for some 9+ months) | Cryomaceration seems—like carbonic maceration—to reference a winemaking technique bearing a similar name. The first time I ever tasted this process it came from Luiz Saldanha Rodriguez at Fazenda California in Brazil, where he developed what he called his “Cold Soul” process, which is a form of cryomaceration. Though there are of course variations, all follow some standard formula of placing whole ripe cherry in a closed container filled with very cold water (8-10º) where it is allowed to ferment—often for days or weeks—before being dried in cherry. I’ve seen producers in Palestina, Colombia ferment pulped coffee under 10º water for 160 hours (as they’ve found it improves the “tail of the devil” flavor common to the selection of Castillo prevalent in their region), but to my knowledge, none of them refer to the process as “cryomaceration.” | Cold Soul |
| Thermal shock | Yes | Very hot and then very cold | Sometimes—usually | Days | This process—like a couple on this list—is best attributed to Diego Samuel Bermudez. While Diego very commonly will ferment cherry in low-oxygen environments (see: “Anerobic”) prior to pulping, and then ferment coffee underwater at precise temperatures after inoculating with yeast (see: “Yeast”) or other cultures, what sets Thermal Shock apart is the washing process: after fermentation, coffee is washed first with hot water (at 40º) and then cooled rapidly by washing it again with water at 12º. It’s like the hot tub-to-pool spa ritual —but for coffee. | |
| Tree-dried | No | A tree | No | Until it’s done | It’s as simple as it gets—and probably the only process that should actually be called “natural.” Coffee is allowed to ripen and then dry on the tree. That’s it. There are many risks, there aren’t quality benefits, but it is what it is. | Raisin |
| Thermal Stroke | No | Very hot – 75ºC | Not usually | Many days | This is a weird one—with references and head-nods to hydro-natural-honey processing’s partial dehydration, a low-oxygen environment, and the extreme temperature play of “thermal shock” coffee—but in reverse. In this process, whole cherry is fermented in a closed container low-oxygen environment for about two days, then partially mechanically dried/dehydrated (which in theory should inhibit bacterial activity) at temperatures not exceeding 35º. After that, it’s placed back into that low-oxygen barrel and fermented at 70ºC for almost a day (!!) before completing drying on patios. | Thermophilic |
| Bio innovation | Yes, eventually | Low-oxygen, in sealed clay pots | A culture grown from wild microflora fed bits and pieces of each of the lots processed that year | 100 hours total (84 in cherry and 16 pulped) | Like some others on this list, this process was introduced and marketed by La Palma y el Tucán. This one takes the prize for most ridiculous name—not only does it indicate nothing about the process itself, but it presents with great confidence and poise something that is not exactly new to coffee (in fact it’s similar or related to a couple other processes I’ve described such as the “molecular” process). In this proprietary process, La Palma begins its fermentation in cherry inside of sealed, clay pots (a low-oxygen environment) for around 84 hours. LPET describes the clay as capturing the native yeasts—which then grow into a culture and continue to live inside the porous material through the harvest, meaning that the population should grow in strength and stabilize in population over the course of the harvest as the charge increases. To the delight of many competitors and high-end specialty buyers, it also means no two lots will be identical. After this extended cherry fermentation, the coffee is pulped and washed using the traditional method. It reminds me of the cheesemaking nun from episode 4 of the Netflix documentary series Cooked, but also of one other thing: In places like Costa Rica, Kenya and other regions with concerns about water usage, recycling water at various stages of the process—whether for floating cherry, pulping coffee, or even fermenting or washing coffee (!) has become common practice. This means that at the beginning of the harvest, the water may be crystal clear but by the end it will be dark, turbid and charged with microbial life—kind of like a less-controlled inspiration for the so-called bioinnovation process. Similarly, in many places around the world where fermentation happens in unsealed concrete tanks, the biological charge will build over the course of the harvest to the extent that the tanks will smell of microbes by peak harvest and have visible microbial growth. | |
| High Gravity | Doesn’t matter | Vacuum | Selected yeast | Typically faster | Based on research from the brewing industry, this type of experimental fermentation happens under vacuum. By pumping out air to create a vacuum in the headspace of a steel fermentation vessel (rather than flushing it with a gas like carbon dioxide), fermentation can be accelerated with the added benefit of homogenizing moisture and fermentation metabolites in the coffee pile. | |
| IPA Anaerobic | Yes, eventually | Low oxygen / closed container (twice) | Yes, IPA yeast and hops (after pulping) | ~120 hours in cherry, ~96 hours after pulping | In the US craft beer scene, the sour beer craze followed an IPA craze. In coffee, perhaps, we went from sour coffee of the early 2010s to now reaching back into our nostalgia for bitter tropicals—or that’s my mental picture of how this process came about. This process starts with a 120-hour, low-oxygen cherry fermentation. After depulping, the coffee is again fermented in a low oxygen environment for 96 hours but this time with yeast selected to ferment Imperial Pale Ale style beer and hops added. Hops contain high levels of terpenes which act to stave off spoilage organisms and scent the coffee with the bitter, tropical character typical of this processing style. | |
| Yeast | Sometimes | Not critical to definition/ varies wildly | Yes, at least yeast | Not critical to definition/ varies wildly | I’ve noted in past entries that this method has existed in some form for literally 70 years, but in short: in yeast processing, somewhere along the way—as cherry, as pulped coffee, even post-washing ahead of drying—yeast is added to the coffee at a tremendous ratio to crowd out competing microorganisms and spoilage organisms and select for a certain strain, giving a producer control over the process and the end result. Typically, producers will use a selection of Saccharomyces Cerevisiaeselected from wine making catalogs (like from Lallemand or Laffort—or Lalcafe, which is a selection of wine yeasts from Lallemand’s catalog that have been tested and proven for use in coffee) but using yeasts from beer making is common, too (although I can’t advise it unless you like swampy, cheesy, sweaty coffee). | Inoculated fermentation Yeast controlled fermentation |
| Koji | Sometimes | Temperature varies; must be an oxygen-rich environment during koji growth until fruiting | Yes, at minimum koji | Not critical to definition/ varies wildly | If you haven’t read my post on koji processing—start there. It’s where all of this nonsense began. In koji processing, spores of a mold (known as koji) as sprinkled on the coffee—either cherry or parchment (typically cherry)—and allowed to grow. The metabolism of koji produces enzymes that increase the perception of body by generating amino acids (this done by protease, primarily) as well as break down starches (amylase enzyme), producing fermentable sugars available to other microorganisms for secondary, sequential fermentation. In other words, is a “pre-ferment” fermentation. Like with yeast, is possible to use koji at nearly any stage of processing, but it’s most common to apply koji to cherry. | Koji supernatural |
| Lactic | Often | Low-oxgyen, sometimes a 2% salt solution | Sometimes a starter culture Sometimes salt | Not critical to definition/ varies wildly | La Palma y El Tucan famously introduced this process—or at least named it. Put simply, the goal of this process is to advantage Lactic Acid Bacteria (LAB) and disadvantage other types of bacteria and yeast. There are several ways to go about this, the most common of which is to inoculate the tank with a starter culture (not actually bacteria, for reasons Lucia describes here) often made from fermenting cascara or whole cherries (sometimes with salt added)—but sometimes created using non-coffee fermentation media as well. This method works like sourdough—essentially building a colony of microorganisms that is pitched into the tank to kick start fermentation. Additionally, these fermentations are most often conducted in low oxygen environments, as LAB tend to dominate in anaerobic, acidic environments rich with carbohydrates. One of the more interesting variations I’ve seen recently—first from José Jadir Losada at El Mirador in Huila and then again from Lucia, is to use a 2% salt solution to control the fermentation. This is a traditional formula for lactofermentation, of course, as many types of LAB are either halotolerant or halophilic—and seems to produce clean, repeatable results with inexpensive inputs (it reminds me of a producer in Hawaii that floats their cherry with salt water. This was the first time I ever experienced the cognitive dissonance of coffee not tasting like I thought it should. I expected it to taste salty: it didn’t). | Salt process |
| Molecular | Usually | Doesn’t matter but in practice usually a closed container | A culture typically grown from coffee cherry | Not critical to definition/ varies wildly | This is a newer process that I’ve seen coming from India. From the outside, it looks very similar to styles of processing like anaerobic or lactic—coffee in a closed container with an airlock on top (in fact I almost dropped it under the “also known as” for lactic process). What makes this style different, though, is that it specifically and always refers to coffee that has been inoculated with a starter culture cultivated from coffee cherry from that specific farm. The idea here is that you’d somehow amplify and control the native microbes found at one farm—creating consistency through the harvest and, depending on the environmental conditions in which that culture was grown (oxygen availability, sugar availability, salt, temperature) selected for certain attributes. Most commonly this coffee is pulped and processed as a wet process. | Very similar to Bio-Innovation |
| Cascara tea | Yes, always | Varies | Cascara — either as dried cascara, fresh pulp, or even freeze-dried cascara, cascara tea, or frozen cascara tea (looking at you, Aida) | Not critical to definition/ varies wildly | Unless you’re Luca—this process typically refers to a style popularized by Aida Batlle where parchment coffee ferments in tea made from coffee skin (or, alternatively, adds frozen chunks of cascara tea to the fermentation. That method helps a lot to combat the 30ºC daytime temperatures in Santa Ana. Or, back in 2017, I tasted a coffee with Aida that she’d processed using freeze-dried cascara tea). Often, lower-quality coffees and hybrids will macerate in tea made from the skin of higher grades (like red bourbon, SL28, etc.). This method tends to add a slight red fruit character and complex acidity to coffee when executed well. | |
| Kombucha | Yes | Varies | A SCOBY | Not critical to definition/ varies wildly | I’ve only seen this process a few times (once this year from Unblended Coffee out of Colombia), but the distinctive part of this process is that rather than inoculating the fermentation with commercial yeast or a starter culture made from cherry, it’s inoculated with a SCOBY (“symbiotic culture of bacteria and yeast”) typically used for producing kombucha. Most SCOBYs that I’m aware of contain high levels of LAB and AAB as well as yeasts like Schizosaccharomyces pombe, Brettanomyces bruxellensis, Saccharomyces cerevisiae, and Zygosaccharomyces rouxii (Villarreal-Soto et al., 2018). In other words—while the population may differ between a SCOBY and a spontaneous coffee fermentation, they contain many of the same species, allowing the Kombucha process to have a jump start in fermentation. | |
| Yogurt | Yes | Varies | Yes, a yogurt culture | Not critical to definition/ varies wildly | This is related to the Lactic process, in many ways, as well as the Kombucha process—almost so much so that it’s not worth mentioning as a separate process except that it specifically refers to coffee that was inoculated with yogurt starter cultures to kickstart fermentation and attempt to select for those specific LAB—all of which may have different sensory characteristics and require different environmental conditions (think of the “yogurt” setting on your Instant Pot, here) | |
| Flower cultured | Yes | Ambient, exposed | Yes, a starter cultured from coffee blossoms | 3 day fermentation | Most of the time, when producers use a starter culture grown from material on their farm, the microbial population is not known. In the case of flower-cultured coffee, however, the producer that developed the process (Aquiares in Costa Rica) identified the yeast growing on freshly-opened coffee blossom (Metschnikowia pulcherrima and Hanseniaspora genus yeasts—both of which also grow on wine grapes), and then, they say—cultured them on agar. Once this culture was established, they used it to inoculate coffee at 5% concentration with water and pulped coffee, allowing the fermentation to progress for three days before drying the coffee. | |
| [Color]-washed | Yes | Not critical to definition/ varies wildly | The juice and/or pulp of a coffee | Not critical to definition/ varies wildly | A variation on washed coffees that does a lot of things, “orange” washed coffee is essentially “washing” pulped coffee with macerated cherry juice and pulp and “golden” washed is the same—but sans the pulp. This one is related to cascara processes in its use of coffee pulp in the process. Using water in processing has ecological disadvantages, and also may reduce flavor intensity as many of the compounds produced during fermentation and some inherent to the seed are water-soluble (therefore—at least in theory—by washing coffee we’re essentially diluting the strength of the coffee). By washing the coffee with its own juices and pulp, producers are attempting to preserve the flavor intensity while also adding additional sugars and microbial charge (which will accelerate or at least change the fermentation). | |
| Natural-hydro-honey | Yes, always, eventually | Varies | Water….. sort of | The process requires “interruptions” | I first saw this process from Elkin Guzman at El Mirador in Pitalito, Colombia—but since it’s a relatively simple process to execute it’s been replicated widely. This process is interesting in how it manipulates hydration as a way to select for certain fermentation kinetics. To start, cherry is partially dried (the “natural” part of the process), which allows for the red-fruit dominant notes from dry processes to set in. At this point, the coffee would be too small or dry to pass through a pulper, so it is then rehydrated in water (“hydro”) for something like 36 hours and then pulped. After pulping, it is dried on raised beds with mucilage still attached (“honey”). This process tends to produce coffee that has fruit character typical of dry process coffees but with sweet-tart characteristics more typical of honeys. | |
| Wet hulled / giling basah | Yes, always | Usually ambient | Rarely | Varies, but not dried fully prior to hulling | “Giling basah” is the Indonesian term for this process commonly practised in Indonesia—and literally translates to “wet grinding.” It is very much a product of the challenges of transporting coffee from a smallholder’s coffee garden to a central mill or purchasing point. The wet hulled process starts off very similar to a washed coffee (and is called “semi-washed” for a reason)—coffee is picked and then pulped. At this point, the pulped coffee is placed in bags (usually made of jute) for up to a day—this is typically when it would be brought to the central collection point. After that, the coffee is washed of mucilage, and laid to dry. Unlike in most methods where coffee is dried to less than 13% prior to removing the husk, wet hulled coffee is dried to just about 30% and then milled. The very high moisture coffee (which was hulled wet….. get it?) is then laid out to dry as green coffee to its final moisture content for export. | Semi-washed |
| Monsooned | No | Monsoon conditions | No | Months of contact with monsoon conditions | So — I thought about not listing this one since technically it’s not a primary postharvest process but occurs after coffee has already been dried—but since it’s unique to coffee processing in that it’s a legally protected process (under India’s Geographical Indications of Goods Act) it’s worth a mention (my own interest in rehydrating coffee aside). In the Monsooned process, coffee is dried in cherry then stored until the onset of monsoon season, at which point they are kept in ventilated warehouses for the entirety of the monsoon season (3-4 months) and subjected to the wet wind. This causes the coffee to swell up and pale in color—almost looking like parchment coffee. The process is supposed to simulate the conditions that coffee might have experienced during the British colonial period, when coffee was shipped in wooden barrels via ship—through monsoons and months’ long journeys. I guess you can think of Sumatran barrel aged coffee similar in its intention, in that regard—but while I do favor whiskey processed overtime and subjected to seasonality, I can’t say the same of this coffee which is characteristically earthy, musty, nutty and chocolate with very little acidity. | related: Sumatran barrel aged coffee |
| Deconstructed Fermentation | Yes, eventually | The pulp and juice are fermented separately from the coffee, then reunited later. and then the coffee is washed with very hot and then very cold water | A culture grown from bits and pieces of coffees that was inoculated with a selected strain of yeast cultured and grown in coffee juice | Very long… days… weeks… | This is the process that kicked off the now-infamous “adulterated coffee” controversy and which members of the Espresso Aficionados Discord server refer to, in a tongue-in-cheek manner, as “illegal coffee.” It combines almost every other process on this list in some way—carbon dioxide flushing, low oxygen fermentation, swabbing and culturing specific strains of yeast, growing a culture from bits and pieces of coffees inoculated with that one strain, back slopping the the fermentation, and thermal shocking. This is basically like the final exam in calculus when the teacher has been telling you all semester, “everything is cumulative.” Diego Samuel Bermudez developed this highly sophisticated protocol. The flavor outcomes depend on the inputs, timing, and selection of microorganisms, but I’ve provided a generalized overview here (I highly recommend Barista Hustle’s post on the process). Essentially, ripe (or overripe) cherry is washed with oxygenated water (to knock back spoilage microbes) then fermented in steel bioreactors flushed with carbon dioxide. As the cherry breaks down and juices are released, those juices are collected. Diego and his team then select a strain of yeast they’ve cataloged and grown into a culture on agar and add it to the separated cherry juice (Each of the strains is selected for a specific, known sensory outcome which is partly why many of Diego’s coffees taste so loudly of one type of fruit or flavor). This inoculated juice is then used to ferment mucilage and pulp (collected from many lots) in a second bioreactor to prepare the culture for the final fermentation phase. When the culture is ready, coffee from the first bioreactor is pulped and the seeds, mucilage and culture from the second bioreactor are fermented together in a new bioreactor. That final fermentation is allowed to progress as long as needed—often 4-5 days. Finally, the coffee is washed using Diego’s Thermal Shock technique. | Lychee |
Hey Christopher, thank you so much for this elaborate overview. This really helps re-arranging some false learnt basics. Great work!
I wonder if the use of “wild” yeasts here is overstated. I remember one study I saw on microbiologists beer podcast that looked at yeasts strains isolated from an apple orchard. Turns out the conventional wisdom of yeasts being on fruit actually yielded very few yeast cells. Moreover what was found were all ID’d as domesticated brewers yeast. One hypothesis given was that the idea originated from winery’s claiming to utilise “wild ferments” without a culture when in fact they had been dumping lees from previous ferments out onto the vineyard; unwittingly pre inoculating the grapes with domestic strains of yeast. In fact fruit was found to be one of the worst sources of microbacteria, rather wild strains were found in forest undergrowth and in bark.
I think given the pervasiveness of domesticated yeast it would be a stretch to call a ferment wild just because the source of the yeast is the environment.
I prefer the the term “wild” to “native” as, unless the work has been done to swab and identify specific strains, the mix is unknown (they might not be native / they might be domesticated species that escaped / they might be a mix / they might be something else). I’ve cited work in past blogs indicating the populations of microorganisms present in coffee fermentations (yeast and other fungi as well as bacteria—the diversity is staggering) as well as the work of Amy Dudley to identify a genetic “fingerprint” of coffee fermentation based on the prevalent strains of yeast, and overall the concept and language holds: a spontaneous fermentation is triggered by unknown yeast and bacteria present in some way in the environment that has not been selected specifically.
Interesting, in the beer and wine industry “wild” is often used in a way that implies “native” at least to the degree that it is used as a marketing term. I’ve often had it put to me that “wild” ferments are somehow more natural or more representative of terroir than inoculation with a known culture. However, given microbacteria’s rapid and stochastic variations I think it’s hard to say that any spontaneous fermentation is necessarily composed of a native composite of microfauna. Although wild ferments would certainly differ from farm to farm and offer unique and diverse ferments, much of these differences wouldn’t be endogenous to the environment.
Chris, there is a tiny factual mistake here:
“Graciano Cruz in Costa Rica around ~2010”
should be:
“Graciano Cruz in Panama around ~2010” (and possibly you can add El Salvador-Chalatenango as well)
Ahhh grateful for the proof read and correction! Updated
Hi !
The table is super useful !
Thank you
Is there a pdf version of it ?
Thank you
Hey! Yes, you can download it to PDF from the Google Sheet I linked.
Thank you! Great glossary with fantastic information.