If you've ever tasted Mandheling coffee, that rich woody, herbal, or even medicinal flavor is the hallmark of the "wet-hulled" method. Because Sumatra experiences frequent rainfall and high humidity, it's difficult to dry coffee beans. To survive, locals devised an ingenious method: they forcibly hull the beans while they are still very wet (with a moisture content of 30-50%) and then directly sun-dry them naked.
This method is risky. Without the protection of the parchment, the beans are like stripping off clothes and sunbathing, making them highly susceptible to damage or mold. They can even be crushed into "goat's hoof beans" by machines. But it's paradoxical: it's precisely this slightly flawed fermentation and oxidation process that creates Mandheling's unique low-acid, rich flavor with hints of cedar and caramel. However, because of the high defect rate, the beans must be repeatedly hand-sorted to achieve a clean and rich cup of Mandheling.