>>21449607The major difference between nuoc nam or colatura d'alici, and true liquamen/garum is in the inclusion of the entrails.
Modern fish sauces gut the fish, then pile them with salt. This simply produces a saline extract of the oils and proteins from the meat and skins of the fish.
A true garum includes the entire digestive tract, they don't gut the fish prior to layering with salt. The digestive enzymes then proceed to break down the fish, it essentially digests itself, which results in a more nuanced flavor that is less fishy and more meaty.
Also, garums were commonly made from a variety of fishes, including mullet, tuna, mackarel and anchovy, as opposed to modern fish sauces that are usually only anchovy. Another key difference is that garum often included other spices and herbs than just the fish and salt, which were unique to each branded formulation. One of the most popular ancient liquamen brands was made with a proprietary blend of aromatic resins and spices, including cumin, rosemary, lovage and coriander.