Natural processed coffees (also called dry) are capable of beautiful tropical fruit, dried fruit and rum cocktail like flavours. They are relatively low in acidity (compared with the washed process), fuller in body and are perceived as sweeter. It was a natural processed coffee which really kicked off my love for specialty coffee, and I know many other people who say the same thing. Full, juicy flavours of peach and strawberry are not usually expected in coffee, but when it balances well they can be among the most delightful drinks.
Brazil and Ethiopia are most known for their natural processed coffees. This is mostly because of a lack of water, rather than any desire to produce a certain flavour profile. The washed method uses high volumes of water and requires special structures for processing. Sometimes it is the only method available to farmers and millers without access to water or capital.
The Natural Process
In the natural (or dry) process, coffee beans are left in their skin and fleshy fruit casing. The cherries are laid out on patios or raised beds under the sun or in shade. For up to a month, the beans undergo a sugar fermentation, where they develop their unique, exciting profile.
Flavours associated with terroir and variety can be somewhat muted by these more fermented tastes. For this reason, there are some in the industry who dismiss dry processed coffees. They were once entirely overlooked by the specialty industry, but this mindset is now outdated. Although natural processed coffees have similarities, they exhibit plenty of different profiles that cannot be merely considered a result of processing. It would be like criticising any method of processing for producing coffees with recognisably similar qualities. No one would say that for washed or honey processed coffees.
To return to producing natural coffees, a huge amount of labour is required to ensure quality. Firstly, as with any specialty coffee, only the ripest cherries should be harvested. Once the coffee is drying, workers pick out unripe, damaged or mould infested fruits and any debris. The coffee must also be turned regularly to increase airflow and not trap damp or mould susceptible points.
When the raisin-looking coffee is sufficiently dried, it is milled to remove the tough skin. The naked beans should have now been dried to a moisture content of around 12%.
Risks associated with the Natural Process
There are risks involved with dry processing coffee which can dramatically reduce a farmer’s yield. For this reason, where there is an abundant water supply, many wouldn't dream of laying their coffee in the sun without removing the flesh and mucilage first. Mould can easily set in if cherries are not tended to. This means constant supervision of the harvest, turning the cherries for better air flow and removing any which show signs of mould.
Furthermore, sorting before processing is not always as vigorous as with the washed process. Washed coffees are sorted in water tanks, looking out for floating cherries which are not perfectly ripe for processing. There is also a sorting stage during pulping, a process which strips the flesh off the bean through pushing coffee against screens under high pressure. Fruit is shredded off the beans allowing them to pass the screen. Unripe cherries, too hard to be pulped and too large to pass the screen, are left behind.
Through all this we can see that some defects are more associated with the natural process than others. And these defects can taste truly awful.
Defects associated with the Natural Process
Debris – Sticks, stones and other material can get picked up along with all the coffee.
Insect Damage – Insect damaged beans are difficult to spot. When coffee is left outside in the open it is susceptible to insect attack. Beetles will bore into coffee and leave them open to fungal infection and diseases.
Quakers - Quakers, or what I like to call bread beans, are under-ripe beans which have little to no sugars. After roasting they appear much paler than the rest of the browned coffee beans. This is because reducing sugars are not present to kick off the Maillard Reaction; an irreversible chemical reaction which makes bread, steak and other browned foods smell so delicious during cooking.
To taste what a quaker can do for your coffee, eat one whole. Its sesame seed bread flavour is not so unpleasant. In the brew though it can taste as bad as off-peanuts.
Phenolic Flavour – Not caused by dry processing as such, but many natural processed coffees are so because of the hot and dry environment. This defect can occur because of such an environment, and it gives a medicinal or iodine taste to the coffee. Ultra Violet light can sort beans with this defect.
Over-Fermented – Over ripe and over fermented beans have an unpleasant sourness. Think sour onions, vomit and delicious manure. MMmmm.
Natural processed coffees add great variation to our collection of profiles. I believe, without their contribution, specialty coffee would not convert as many as it does to the industry. Their inclusion is only a good thing, building on the once lonely world of washed coffees. Thinking of them in this way may already be outdated, with new variations in processing fruiting in abundance. People are innovating and experimenting with different yeast cultures, mixed processing methods, micro-controlled honey processing and many more.