Natural-processing, also known as dry-processing or sun-dried method (unwashed), is a traditional way of processing coffee. After harvesting cherries from the coffee trees, they are submerged in water to remove impurities and immature fruits.

The cherries are then spread out under the sun to dry. Depending on the farm, each farm does it differently: some use brick patios while some use raised beds. To prevent the fruits from spoiling, the cherries are turned regularly throughout the day and covered at night to protect them from the rain. This process can take up to anywhere from 3-6 weeks. During this period, the beans are fermented in the cherries.

After the cherries are dried, the seed will be separated from the skin and dried fruit flesh mechanically. What is left on the coffee beans then, will be a thin layer of skin known as the parchment skin; this skin will be removed through the last step which is also known as hulling. Thereafter, the coffee green beans are stored away to be rested.

This conventional method of coffee processing is common in regions like Ethiopia and some parts of Brazil. This process adds depths to the coffee’s flavours in terms of fruitiness and sweetness. Common flavour notes are berries and chocolate.

Pick Ripe Cherries
In the picking stage, the level of ripeness and elevation of fresh fruits (cherries) are critical. Red and purple-red cherries produce the best flavours, while under-ripe (green) and over-ripe cherries produce astringent tastes which deteriorate the overall cup-quality. Often, red-cherries grown at higher altitudes are highly demanded as it produces better flavours due to better maturity and higher sugar content.
Submerge in Water
Submerging is a process of removing impurities from the harvest. Through the fluidity and gravity of water, the immature fruits, floaters, withered beans, sticks and leaves are removed. When the fresh cherries are submerged in water, the pulp which carries microorganisms will hasten the fermentation process.
During fermentation, microorganisms in mucilage will react with sugar to degrade, leading to fermentation. This is an essential stage of coffee processing as this is when microorganisms interact with enzymes and amazing flavours are developed. The coffee fragrance changes from fresh fruits to berry-like, transforming into tropical fruits and rich red wine - the ideal state of natural fermentation.
Drying is a phase where the quality of the green bean and developed coffee flavours are preserved. Typically, drying takes about 23 days and during this period the water content in the coffee beans are reduced to the appropriate range at around 10-12%. Usually, drying is done with a suitable temperature through using convective hot air
Hulling is one of the final stages in processing coffee. It involves removing the last layers of dry skin from the now-dried coffee - the parchment skin (also known as ‘pergamino’). Parchment is a naturally formed substance that covers the coffee bean. After coffee beans are dried, the parchment skin is crumbly and dry, making it easy to be removed by a machine called “huller”.