The only difference between green olives and black olives is ripeness. Unripe olives are green and fully ripe olives are black. Olives are cured or pickled before consumption, using various methods including oil-cured, water-cured, brine-cured, dry-cured, and lye-cured. Green olives must be soaked in a lye solution before brining, whereas ripe black olives can proceed straight to brining. The longer the olive is permitted to ferment in its own brine, the less bitter and more intricate its flavor will become.

The USDA database did not test green olives or specify the curing/pickling process used on the black olives that were tested.