Garum is a type of condiment that was used to season food during the time of the ancient Romans. It was often made from fish that was left to ferment and combined with various herbs and plenty of salt. The condiment was enjoyed by both the wealthy and the lower classes in ancient Rome and was used to season a wide variety of foods, either in recipes or at the table. It was often mixed with wine or vinegar and used as a dressing.
The Romans got the idea for garum from the ancient Greeks, who were using the sauce as far back as the fifth century BC. Its name comes from the Greek word for a specific kind of fish, garos. Later on, in the first century BC, garum was produced in parts of Spain, including Barcelona and New Carthage. At the time, Spain had a large fish salting industry and became renowned for its garum.
Mackerel is usually the preferred fish for the condiment, and produced the most expensive garum. A less costly condiment could be made from tuna fish. Sauce made from tuna was referred to as muria. The least costly version of garum was made from whatever fatty fish a person could get his hands on and was often referred to as liquamen.
Pliny the Elder, the Roman historian, preferred the sauce made from mackerel and gave his name to it: Pliny Garum. The sauce was produced by taking the blood from a freshly caught mackerel and mixing it with the fish's entrails and other usually wasted parts of the fish. That mixture was then salted and left to sit in the sun for several weeks or months, during which time it would ferment.
During the fermentation, the fish would break down, resulting in a brownish liquid. At the end of the fermentation period, the solid parts of the fish would be separated from the liquid. The remaining fish solids, which were known as allec, were often used on their own as a paste to flavor dishes.
Roman taste for garum died out around the 16th century. A new kind of fish paste, made from anchovies that were salt cured, took its place in Roman cuisine. A more tame version of the sauce can be made at home by reducing a quart of grape juice and then mixing a bit of anchovy paste into it. Another modern day descendant of the ancient sauce is Worcestershire sauce, which more often than not, contains an anchovy paste.