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Post-Harvest Processing, Milling, and Grading
Post-Harvest Processing

• General: The coffee fruit is similar to a cherry, with a skin, pulp, and a (double) pit. The skin and pulp have to be removed, and the seeds dried, so they can be shipped and roasted.

• Wet Processed or Washed: The skin and pulp are removed by fermenting them quickly, and washing them off. This creates brighter, cleaner, and lighter bodied coffees.

• Dry Processed or Natural: The skin and pulp are allowed to dry over a week or so, they are then easily peeled off. This creates a heavier bodied, sweeter, more subdued coffee that can be tainted by ferment flavors.

• Pulped Dry Process or Semi-washed: The skin is washed off, but the pulp is allowed to dry on the bean over 24 to 48 hours. This creates an intermediate between dry and wet process coffee.

• Patio or Sun Drying: After being depulped, the beans are dried on patios or platforms by the sun. This is considered preferable to kiln drying. Kiln drying is used when an overly humid climate can rot beans left to dry in the sun.

Post-Harvest Milling Information

The first step in dry milling is the removal of what is left of the fruit from the bean.

Hulling is done with the help of machines, which can range from simple millstones to sophisticated machines.

Most specialty coffee goes through a battery of machines that sort the coffee by density of bean and by bean size. Sticks, rocks, nails and other material is removed here as well. There are added sorting steps done here prior to grading.

The final step in the cleaning and sorting procedure is called color sorting, or separating defective beans from sound beans on the basis of color rather than density or size. Color sorting is the trickiest and perhaps most important of all the steps in sorting and cleaning. With most high-quality coffees color sorting is done in the simplest possible way: by hand. Teams of workers pick discolored and other defective beans from the sound beans. The very best coffees may be hand-cleaned twice (double picked) or even three times (triple picked). Coffee that has been cleaned by hand is usually called European preparation; most specialty coffees have been cleaned and sorted in this way.


This process is done by certified graders in each country and there are varying Grade levels for each coffee, typically 1-4.

Grading is based on categorizing coffee beans by size of the bean, altitude, how it was prepared and picked on a particular farm or harvest cycle, and most importantly, how good it tastes or its cup quality. Coffees also may be graded by the number of imperfections per sample. For the finest coffees, origin of the beans makes a big difference in its grading. Some growers want to impose quality control for grading because of desired price points for limited edition or very specialized crops.

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