By Harold McGee
Preservation by natural drying works well in cold and hot climates. Temperate Europe, where fish generally spoil before they can dry sufficiently, developed the habit of salting fish first, or instead. A day’s salting would preserve many fish for several days more, long enough to be carried inland, while saturating the fish with around 25% salt keeps it stable for a year. Lean cod and relatives were salted and then air-dried, while fatty herring and their ilk were guarded from air-induced rancidity by immersing them in barrels of brine, or by subsequent smoking. The best of these are the piscatory equivalent of salt-cured hams. In both, salt buys time for transformation: it preserves them long and gently enough for enzymes of both fish and harmless salt-tolerant bacteria to break down flavorless proteins and fats into savory fragments, which then react further to create flavors of great complexity.