Moisture content
also: green moisture, moisture level
The water percentage in green coffee; roughly 10 to 12 percent is the storage sweet spot.
Moisture content is the percentage of water held inside a green coffee bean, measured by weight. After processing and drying, coffee is dried down to a target window of about 10 to 12 percent before it is bagged, with roughly 11 percent often treated as the sweet spot.
Why it matters: moisture sits at the center of how stable and how good coffee stays in storage. Too high (much above 12.5 percent) and the beans risk mold, fermentation taints, and faster staling. Too low (under about 9 to 10 percent) and the coffee can taste flat, papery, and brittle, having been over-dried, often on poorly managed drying beds or in rushed conditions.
In the cup, off-target moisture shows up as muted sweetness, baked or woody flavors, or musty defects. Roasters also care because moisture affects how a bean takes heat and reaches an even roast. Note that moisture content and water activity measure different things: one is total water, the other is how available that water is to microbes.