Black pepper is produced from the still-green unripe drupe of the pepper plant. The drupes are cooked briefly in hot water both to clean them and to prepare them for drying. The heat ruptures cell walls in the pepper speeding the work of browning enzymes during drying. The drupes dry in the sun or by machine for several days during which the pepper skin around the seed shrinks and darkens into a thin wrinkled black layer. Once dry the spice is called black peppercorn. On some estates the berries are separated from the stem by hand and then sun-dried without the boiling process.