Coffee processing
A coffee cherry is a wet, sugary fruit around a seed, and it starts to spoil the day it is picked. Processing is everything done between the tree and the sack to turn it into a dry seed that will keep. The methods differ mainly in one decision: how much of the fruit is still on the seed when it goes out to dry.
These pages are written from international guidance on processing and from published trials, and they keep two things apart that are usually run together: what is done to the coffee, which is well documented, and how it then tastes, which mostly is not. You will find no fermentation time to aim for here and no promise that a process tastes a particular way.
Four routes from the same cherry
Where the processes part company
CoffeeHQ diagram
Natural
- SortOften by floating the harvest in water.
- Dry the whole cherrySkin, flesh, mucilage and parchment all on.
- HullDried fruit and parchment come off together.
Pulped natural and honey
- Sort and pulpSkin and most of the flesh removed by machine.
- Dry in the mucilageSome or all of the sticky layer left on the parchment. No tank, no washing.
- HullParchment comes off the dry seed.
Washed
- Sort and pulpAs above.
- Remove the mucilageFermented until it washes off, or rubbed off by machine.
- WashSometimes followed by a soak in clean water.
- Dry in parchmentOnly the parchment is left around the seed.
- HullParchment comes off the dry seed.
Wet-hulled
- Pulp, ferment and washAs for washed coffee, on the farm.
- Hull while still wetThe parchment comes off before drying.
- Dry the bare beanNothing is left around the seed.
The order of steps in each process family, as described in the Food and Agriculture Organization's guidance on coffee processing and, for wet hulling, a study carried out for it in North Sumatra. No times or moisture figures are shown: they differ between farms, and none read is a target.
Read across the lanes at the drying step. A natural goes to the yard as a whole fruit, a honey as parchment in its mucilage, a washed coffee as clean parchment, and a wet-hulled coffee as a bare bean. Most of what separates the methods in cost, water, risk and reputation follows from that.
What the sources say about each
The table reports what a document says, with the method page giving the source. It has no column for taste, because no document read for these pages compared the processes on the same fruit with a tasting panel.
Four process families compared on what is documented
CoffeeHQ explanatory model — not a measurement
| Process | What goes to the drying yard | Water used before drying | Where fermentation happens | Where the sources place the risk |
|---|---|---|---|---|
| Natural | The whole fruit. Almost twice as much water to remove as from washed coffee, for the same green coffee. | None before drying, unless the harvest is floated. | Unplanned: inside the drying fruit, and in heaps or sacks if cherries are held before spreading. | A slow start on the yard and a long time wet; the fruit protects the seed. |
| Pulped natural and honey | Parchment coated in mucilage. | Pulping water only. | On the drying bed. One study found different microbes active depending on how much mucilage was left. | A wet, sugary coating that has to be turned and dried through. Not measured in any document read. |
| Washed | Clean parchment. | The most. One study of Ethiopian mills found 22 litres a kilogram with working recycling and 63 without. | In a tank, to loosen the mucilage, unless a machine removes it. One trial found its length changed the cup more than anything else it varied. | The fermentation itself if it runs on, and the wastewater. |
| Wet-hulled | The bare green bean. | As for washed coffee. | As for washed coffee, before the coffee is sold wet. | Time spent wet in trade and storage. The study that described it was investigating mould. |
Basis: The Food and Agriculture Organization's guidance on preventing mould in coffee, a study of wet processing in Yunnan, a study of wet mills in Ethiopia, a study of honey processing and a study of wet hulling in North Sumatra. Limits: Each cell is one source's statement about the general case or about one site. Practice varies between countries and between mills, and the water figures in particular are from a single river basin.
Process and taste
The trade has a shorthand: washed coffees are clean and bright, naturals heavy and fruity, honeys in between. It is a fair description of what buyers expect and it is how coffee is sold. It is not a finding. The guidance these pages rest on says only that coffee dried in the cherry and coffee dried in parchment have different sensory qualities, and adds that many claims linking a processing step to quality have never been tested against an alternative.
What published trials do show is that the same fruit can be made to taste different within one process, by fermenting it for longer or by adding a chosen yeast, and that the word on a bag changes what people report tasting. So a process name is worth reading as a description of what was done, and worth testing for yourself: washed versus natural sets up the comparison, and the Tasting Lab gives you a worksheet for doing it blind.
The stages every process shares
- Fermentation
What ferments, which microbes do it, and what trials found when they changed the time or chose the yeast.
- Drying
Three phases, the moisture and water activity limits in international guidance, and what happens on the yard.
- The newer process names
Anaerobic, carbonic maceration, thermal shock, co-fermented and infused, as words first and science second.
The methods, one at a time
- Washed (wet) process
The fruit is taken off before drying: the cherry is pulped, the sticky mucilage left on the seed is fermented or rubbed off and washed away, and the seed is dried in its parchment.
- Natural (dry) process
The whole cherry is dried with the fruit still around the seed, and the dried fruit is hulled off afterwards. No pulping and no washing water, and the most water to dry out.
- Honey process
The cherry is pulped and the seed is dried with some or all of its sticky mucilage left on. The colour names used for it, from white to black, are not standardised.
- Pulped natural
The cherry is skinned and the seed is dried in its mucilage with no fermentation tank and no washing. The name is the English one for Brazil's cereja descascado; in outline it is the same as the honey process.
- Wet-hulled (giling basah)
Used in northern Sumatra: coffee is pulped, fermented and washed, then has its parchment hulled off while still wet, so that the bare green bean is what gets dried.
- Anaerobic fermentation
A step, not a complete method: cherries or pulped coffee are fermented in a closed container before being dried as a natural, honey or washed coffee. The word is used loosely and is not defined by any standard.
- Carbonic maceration
A term taken from winemaking, generally used in coffee for whole cherries fermented in a vessel filled with carbon dioxide before drying. It is not defined by any standard, and CoffeeHQ has read no study of it in full.
- Thermal shock processing
A producers' term, usually described as moving the coffee between hot and cold water at some point during processing. CoffeeHQ has found no study of it and says nothing about what it does.
Processing where it happens
Processing is decided by climate, water and what a buyer pays, so it reads best in a country's own setting. Brazil explains why pulping was adopted beside the natural process, Indonesia sets out the wet-hulling trial in full, Ethiopia shows washed and natural following the price of cherry, and Colombia is a country of washed coffee. As a course, Coffee Expert level 5 covers the same ground with exercises.