The Complete Handbook of Fish Sauce

Chapter 1: Understanding Fish Sauce

Fish sauce is a translucent, amber-to-dark-brown liquid produced by the controlled fermentation of salt-packed fish, most commonly anchovies. The process is straightforward in principle: fresh fish is mixed with sea salt at a ratio of roughly two to three parts fish to one part salt, packed into large wooden vats or concrete tanks, covered with a brine layer, and sealed for six months to two years. During that time, the salt draws water out of the fish and prevents putrefactive bacteria from thriving, while enzymes naturally present in the fish's digestive tract break down muscle proteins into peptides and free amino acids. The resulting liquid is drained from the bottom of the vat, filtered, aged in the open air, and bottled. That is the entire process, and the enormous variance in quality, flavor, and price across fish sauces comes from variations in fish species, salt quality, fermentation time, pressing method, and whether the producer adds water, sugar, or caramel to stretch the yield.

The central chemical event is proteolysis. Fish muscle tissue is roughly 18 to 20 percent protein by weight. When the fish dies, autolytic enzymes - primarily trypsin and chymotrypsin from the digestive organs - begin breaking down those long protein chains into shorter peptides and individual amino acids. This is the same process that tenderizes meat during aging, but in fish sauce it is carried to extremes. The most important amino acid released is glutamic acid, the ionized form of which produces