Processing prior to exporting is called thrashing. The stored beans are transported out of the storage bins/silos by machines. All of the precautions adhered to during storage should continue to be followed even after loading onto transports. It is important to ensure that all transporting equipment such as containers is clean, and has no holes or smell that could impair the quality of the beans. Loading should be done in dry conditions, not under rain or direct sunlight. The coffee beans should continue to be handled with the utmost care to minimize the chances of contaminating them.
Once transported to the thrashing unit, the parchment beans are processed into green beans.
Once the beans are dried, all of the layers are removed from the beans. This process is called hulling and is accomplished by using a hulling machine. Wet-processed coffee has the dried hull removed, while dry-processed coffee has the entire husk removed.
Occasionally, coffee beans may be polished in a polishing machine to remove the last bit of silvery skin coating the beans.
Beans are then graded and sorted, first by size, then by density. A screener sorts the beans according to their size. A densimeter sorts the beans by density, into three or more groups by density. Some defective beans (broken, small and undeveloped) are also removed in this process. The beans can further be sorted by an air jet that separates lighter (inferior) beans from heavier (superior) ones.
Since the above steps do not remove all defective beans, manual intervention is necessary to remove the rest. Alternately, a machine can be used to discard beans with colours different from the ideal blue-green colour, and sort the rest according to their colour characteristics.
Once graded, the beans are packed. Coffee is typically shipped unroasted. These beans are called green coffee.
“An Introduction to Good Manufacturing Practices for Post Harvest Processing of Arabica Coffee in Vietnam” - Jan. C von Enden.
Coffee Research Institute
Intelligentsia Coffee & Tea, Inc
INeedCoffee – The Coffee Mill
On the Road to Quality. Made by Kraft foods Germany, Vietnam Coffee Cocoa Association VICOFA and Dtsch. Gesellschaft für technische Zusammenarbeit (Gtz).
Mr. Jan C. von Enden
EDE Consulting Asia Pacific