Harvesting is one of the most important influences on coffee quality. Coffee processed from ripe cherries is naturally sweet and shimmering with floral and fruit notes. Coffee processed from unripe cherries may taste grassy, green, thin, or astringent. Coffee processed from overripe, shriveled cherries (sometimes called raisins) runs the risk of tasting fermented, musty, or mouldy.
Harvesting coffee is particularly challenging because coffee fruit typically does not ripen uniformly. The same branch may simultaneously display ripe red cherries, unripe green cherries, and dry, past-ripe black cherries.
In regions where labor is inexpensive or where families pick their own small plots, trees may be picked repeatedly, and only ripe fruit harvested during each pass through the trees. In parts of the world where labor is scarce or expensive, coffee may be stripped from the trees in a single picking. Ripe, unripe, and overripe cherries are all gathered together, along with some leaves and twigs. Although sophisticated sorting methods can compensate to some degree for mass picking, no expedient is quite as effective as repeated, skillful hand picking.
Machines have been developed that selectively pick ripe cherries by vibrating the tree just vigorous enough to knock loose the ripe fruit, while leaving the unripe fruit still attached to the tree. Such machines do not approach the selectivity of a good hand picker, and are used only in regions of the world — Brazil, Australia, and parts of Hawaii — where labor is too costly to support hand picking. Almost all fine coffee still is picked selectively by hand.