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Coffee 101 & History > Coffee Harvesting > Coffee Milling > Cupping & Grading

Milling

Wet Method
The "wet" method is primarily used with higher quality arabicas. It is a more expensive process as it is more complex and requires a great deal of water. In this classic method, first the outer layer is gently removed by a "pulping" machine. The next step, called fermentation, is a process of allowing natural bacteria to dissolve away any fruit that may remain on the bean. There are a few types of fermentation:

• Wet fermentation: The beans are soaked in water for many hours to aid in the growth of the natural bacteria
• Dry fermentation: No water is added to the beans, rather they are allowed to ferment in their own juices.
• Aquapulping: A mechanical process used in arid climates which uses much less water and eliminates the need for fermentation. We're helping install aquapulping equipment in Kenya. Read about our Kenya Project.

Following fermentation or aquapulping, the beans are dried on large concrete patios or elevated drying beds. Depending on the weather, the drying can take up to several days. During the drying process, the beans are constantly raked or hand stirred to ensure even drying and to prevent any build up of microorganisms. In some countries, like Africa, defective beans are sorted out by hand at or near the end of the drying process.

Dry Method
The "dry" method (sometimes referred to as naturals or unwashed) involves picking the beans from the plant and simply allowing them to dry in the sun naturally on large drying patios. This method of drying can take up to three weeks. Once fully dried, millstones or machines are used to remove the husk. The "dry" method is most commonly used in regions that lack an adequate water supply.

Pulped Naturals
Most commonly found in Brazil and certain parts of Indonesia, this method is similar to the "wet" method. The main difference occurs after the removal of the outer skin, where the second layer of sticky fruit is allowed to dry on the bean. Once dried, the fruit and the parchment underneath are removed at the dry mill.

Dry Milling
It is at the dry mill that the beans are prepared for shipping. The first step in the dry mill is to remove a final layer of parchment from the green coffee. The parchment has been protecting and allowing the bean to recover or "rest" and is now mechanically removed so that the beans can be sorted and graded. In most dry mills, huge machines are used to remove debris like twigs and stones. Then the beans are sorted by density and size.

Color Sorting
The final step in the milling process is the sorting of beans by color. Although color sorting is the final step in this long process of milling, it may also be the most time consuming because in most countries sorting is being done by hand. More developed countries have begun using machines that optically scan each bean for color but these machines are very expensive and not yet practical in most coffee producing regions.

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