Washed
Mucilage left on:
From tree to bag takes weeks: the clock on the stage shows real time, the animation squeezes the long days of drying and resting.
Seed to Swan
Follow 100 kg of ripe cherries all the way to green coffee: picking, floating, pulping, fermenting, drying, milling and grading. See how washed, natural, honey and experimental processes change the beans and the cup, and what goes wrong.
From tree to bag takes weeks: the clock on the stage shows real time, the animation squeezes the long days of drying and resting.
Everything behind the animation: the cherry and its layers, ripeness, the processing methods, what fermentation does, the experimental processes, drying, the dry mill, grading and defects, pests and diseases, species and origins, and how to judge, buy and store green coffee.
Coffee is the seed of a fruit. Under a thin skin sits sweet pulp, then a sticky layer of mucilage, then a paper-like shell, the parchment, around each of two seeds. Processing is the art of getting those seeds out and dry, and every way of doing it changes the taste.
A fresh cherry is about two-thirds water, the seed inside about half. Green coffee is dried to 10–12 %; roasted coffee has only 1–3 % left.
About 5 kg of ripe cherry make 1 kg of green coffee; it takes more than 1,500 cherries for a pound (450 g). On the stage: 100 kg of cherry give about 19 kg.
About 5 % of cherries grow a single, round seed instead of two flat ones. They are sorted out and sold apart (“PB”); not better by nature, but different.
Skins and pulp become compost, or are dried and sold as cascara tea; dried husks from naturals can be burned as fuel for dryers.
Only ripe cherries make sweet coffee, and they don’t all ripen at once: one branch can carry green, yellow, red and overripe cherries together. Picking well means going back to the same trees again and again.
Every method has the same goal: get the seed out of the fruit and dry enough to keep. What stays on the seed while it dries, and for how long, changes the cup more than almost anything else; green-coffee buyers put the process first, before origin and variety.
The colour names say how much mucilage stays on and how dark the parchment turns as it dries (the mucilage oxidises). There is no fixed standard: every mill sets its own. Honey became popular in Costa Rica when water rules after the 2008 earthquake made traditional washing harder.
All coffee ferments. From the moment a cherry is picked, wild yeasts and bacteria start eating its sugars. For centuries this was simply the way to get the mucilage off; only in the last ten years or so have producers started to steer it for flavour.
Yeasts turn sugar into alcohol, CO₂ and fruity esters; lactic bacteria into lactic acid (round, creamy). With air, acetic bacteria turn alcohol into acetic acid: a little is brightness, a lot is vinegar. Acids and aromas seep through the parchment and become flavour in the roaster.
About 18–25 °C is comfortable. Cold: slow and flat. Warm: fast, and it can run away into sour, vinegary flavours. In hot weather a washed tank can be done in 6–12 hours; in cool weather it takes 24–48.
Too short and the mucilage won’t wash off and the flavours stay undeveloped; too long and it turns sour, boozy, rotten. Riper, sweeter cherries ferment into sweeter, fuller coffee; unripe ones give sharp, astringent cups.
A stick pushed into the mass stands up by itself, and a handful of seeds rubbed together feels and sounds like gravel, not slime. These tests say the seeds are clean, not how they will taste.
Cheap pH meters, Brix refractometers and thermometers made fermentation measurable. The pH falls as acids build up (5.4 → 4.3 in the washed tank on the stage); the Brix falls as the sugar is eaten. Most producers use them as guardrails, not as a stop sign.
Fermentation is by definition life without oxygen, and even open tanks drop below 2 mg/L of dissolved oxygen, the line winemakers use. On a bag it just means “sealed for a while”: 24 hours in a plastic sack and 10 days in an engineered tank carry the same word. Ask what was done.
Most coffee ferments with whatever lives on the fruit and in the air. Adding a chosen yeast (e.g. Saccharomyces) or lactic bacteria makes it more predictable. Salt is the cheap trick: lactic bacteria tolerate it, most yeasts don’t.
The same model as the stage. Choose what goes into the tank, the container, the microbes and the temperature, and watch the sugar, acids and alcohol over time. Then run your fermentation on the stage.
All of them take one or more of the fermentation’s levers (oxygen, temperature, time, microbes or what is added) and push it on purpose. Some are now common on green-coffee lists; some are still in the lab.
Freshly processed coffee is about half water and would rot in days. Drying brings it to 10–12 %, slowly and evenly: the seed is still alive. Temperature and airflow do the work; weather, layer depth and turning decide how well.
Hot sun, thin layers, no turning: the outside dries before the inside, beans crack and split (“goat hooves”), and the coffee fades within months.
Thick layers, rain, no turning: the coffee stays wet for days, ferments too far and grows mould: musty, sour, phenolic cups and real defects.
Piled up and covered at night and in rain, the coffee doesn’t soak up water again, and the moisture evens out inside the beans.
Dry parchment (or dried cherry) is bagged and rested for weeks before milling, so moisture evens out from bean to bean; often in airtight GrainPro bags.
At the dry mill the parchment (or the dried husk of a natural) comes off and the beans are sorted until every bag is even: by size, by density and by colour. Density, moisture, size and the defect count are the “four pillars” buyers use to judge green coffee.
Mark a cup where 250 g of water comes to. Dry it, fill it to the mark with green beans (pour, don’t press) and weigh them.
Graders spread a 350 g sample on a black mat and count every defect, then roast 100 g to look for quakers. The Specialty Coffee Association lists 16 defects in two categories; a few beans of the worse kind count as one “full defect”.
Click every bean you think is a defect, then press Check. The tray is a small part of a 350 g sample: count as if it were all of it.
Each one is a normal process with one thing gone wrong. Watch it on the stage and see what it does to the beans and the cup.
Some defects start long before processing, on the tree. The sources here say little about farm diseases beyond the insect holes, potato taste and mould they cause; these cards add the main ones every coffee grower knows.
Nearly all specialty coffee is Arabica; most of the rest is Robusta. Within Arabica, varieties differ in taste, yield and disease resistance, and the same variety tastes different from farm to farm. How the trees grow, the species side by side and each variety’s tree: the Coffee Tree studio.
Why different places use different methods: water, weather, labour and space. Brazil’s dry season and flat land suit naturals; Colombia’s rain and water suit washing; Indonesia’s humidity led to wet-hulling; water rules in Costa Rica pushed honey.
Before roasting a single bean you can learn a lot: the colour hints at the process and the age, and the smell tells fresh from stale.
Green coffee keeps far longer than roasted, but not for ever. Buy what you can taste first, store it well, and know what the price pays for.
Country, region and ideally the farm or lot (a sub-region only usually means a blend of many farms), process, variety, altitude, harvest date, moisture, water activity, density, screen size, defect count and cupping notes.
Roast and cup a 100 g sample before buying; good importers send a pre-shipment sample and another when the coffee lands, to check nothing changed on the way.
Importers handle shipping, duties and bulk; direct trade gives the most traceability, but a roaster buying 5–10 bags can’t easily work with a producer selling 500–600. Home roasters: online green-coffee shops.
“Pick two”: you can’t have all three. Cheap specialty coffee usually means someone in the chain, most often the farmer, isn’t being paid enough.
Cool (about 18 °C), dry (about 60–65 % humidity), dark and airtight: GrainPro or vacuum bags. Jute breathes. Deep-frozen coffee keeps for years; roast it soon after it comes out.
About 12–24 months well stored, a little less for experimental lots. Signs of age: paler beans, straw smell, papery, woody, flat cups (“past crop”).
Caffeine is taken out of the green beans: the Swiss Water process uses water, green-coffee extract and carbon filters (about 99.9 % caffeine-free); solvent methods take out about 97 %. Good decaf starts as good green coffee.
“AA” is a size, not a quality. Fermented coffee isn’t probiotic once roasted. Roasting hardly changes caffeine. The health claims for green-coffee extract on shop blogs are not proven.
What happened at the farm decides how the beans behave in the roaster. See the roasting itself in the Bean Roasting studio.
Washed coffees roast evenly and predictably. Naturals and honeys carry sugar on the surface: they roast faster and scorch more easily, so start gentler. Experimental lots have a narrower good window.
Dense beans (high altitude, cool, slow-growing) take more heat: a hotter start and a quicker browning phase. Soft, low-density beans want a lower charge temperature and a longer, gentler browning: “low and slow”.
Big beans take longer to heat through; small beans and peaberries roast faster. Mixed sizes in one batch roast unevenly, so blend coffees with similar sizes.
Wetter beans (like wet-hulled Sumatra, 12–13 %) need longer to dry in the roaster; very dry or old beans run fast and taste flat. Coffee still holds about 5–6 % water at first crack.