Harvesting, processing, and storage are critical stages that directly affect the quality of green coffee beans for export. Yet many coffee farmers, even those with years of experience, still do not follow proper practices.
Harvesting
Table of Contents
The first requirement is to pick cherries at the right ripeness. To produce high-quality coffee, cherries must be red-ripe or just fully ripe; unripe green cherries should not be harvested. Overripe or dried cherries must also be avoided; if they are present, they should be separated and dried separately.
At least 95% of the harvest should consist of fully ripe or just-ripe cherries (except for the final picking round, when the percentage can be slightly lower). Pick cherries by hand using your fingers to pluck individual cherries—do not strip entire branches or pull off whole clusters, especially with Arabica coffee. Protect branches, leaves, and buds to safeguard the next season’s crop. Avoid dropping cherries on the ground, where they can be infected by fungal diseases.
Initial Handling
Freshly picked cherries should be processed immediately. If processing is delayed, spread the cherries on a clean brick or concrete surface in a cool, airy place in a layer no thicker than 30–40 cm. Do not pile cherries into heaps, which can cause heating and unwanted fermentation. Cherries should never be left unprocessed for more than 24 hours.
Bags for fresh cherries and transport containers must be clean and free of fertilizer smells or chemical residues.
Processing and Storing Parchment Coffee
Two main processing methods are used: dry processing and wet processing.
Wet Processing
This method is commonly used for Arabica and partly for Robusta when required by buyers. After harvest, remove unripe and dried cherries, twigs, leaves, and stones. Ripe cherries are pulped to remove the outer fruit skin. The beans, still covered by the parchment layer (husk), are called parchment coffee.
Next, the sticky mucilage must be removed by soaking and washing—hence the term “washed coffee.” After the mucilage is removed and the parchment is clean, the beans are dried to a moisture content of 10–12%, producing dried parchment coffee.
This dried parchment is then dry-milled to remove the parchment husk and polished to take off the silver skin, yielding green coffee beans, which are then graded and classified for trade.
Dry Processing
Here the cherries are dried whole without pulping until the moisture content falls to 12–13%. This usually takes 25–30 days of sun-drying. The dried cherries are then dry-milled to remove the outer husk and parchment, producing green coffee beans.
Semi-washed (or semi-wet) Processing
A hybrid approach common in Vietnam: cherries are pulped and partially cleaned of mucilage, then dried without full fermentation and washing.
Wastewater and Coffee Husk Management
Wastewater from processing can create odor and pollution if untreated. According to research from the PPP sustainable coffee project, wastewater can be collected and treated, and coffee husks or pulp should be composted into bio-organic fertilizer or placed in biogas digesters.
Food Safety and Mold Prevention
Prevent the growth of molds and contamination with Ochratoxin A (OTA) by practicing strict hygiene. Avoid letting cherries or parchment coffee contact soil, manure, or dirty drainage areas.
Storage of Finished Coffee
Before storage, ensure that green coffee beans have been dried to 11–12% moisture content and are kept dry so that they do not reabsorb moisture. Reduce impurities in the final product to no more than 0.5% to maintain export quality.