A traditional method of processing and preserving anchovies is to gut and salt them in brine, allow them to cure, and then pack them in oil or salt. This results in a characteristic strong flavor and the flesh turning a deep grey. Pickled in vinegar, as with Spanish boquerones, anchovies are milder and the flesh retains a white color. In Roman times, anchovies were the base for the fermented fish sauce garum. Garum had a sufficiently long shelf life for long-distance commerce and was produced in industrial quantities.