Dried fish

Fresh fish rapidly deteriorates unless some way can be found to preserve it.Dryingis a method offood preservationthat works by removingwaterfrom the food, which inhibits the growth ofmicroorganisms. Open air drying using sun and wind has been practiced sinceancient timesto preserve food.Water is usually removed byevaporation(air drying, sun drying, smoking or wind drying) but, in the case offreeze-drying, food is firstfrozenand then the water is removed bysublimation. Bacteria, yeasts and molds need the water in the food to grow, and drying effectively prevents them from surviving in the food.
Fish arepreservedthrough such traditional methods as drying,smokingandsalting.The oldest traditional way of preserving fish was to let the wind and sun dry it.Drying foodis the world's oldest known preservation method, and dried fish has a storage life of several years. The method is cheap and effective in suitable climates; the work can be done by the fisherman and family, and the resulting product is easily transported to market.
Stockfishis unsalted fish, especiallycod, dried by cold air and wind on wooden racks on the foreshore. The drying racks are known asfish flakes. Cod is the most common fish used in stockfish production, though otherwhitefish, such aspollock,haddock,lingandtusk, are also used.
Over the centuries, several variants of dried fish have evolved. Stockfish, dried as fresh fish and not salted, is often confused withclipfish, where the fish is salted before drying. After 2–3 weeks in salt the fish has saltmatured, and is transformed from wet salted fish to Clipfish through a drying process. The salted fish was earlier dried on rocks (clips) on the foreshore. The production method of Clipfish (or Bacalhau in Portuguese) was developed by the Portuguese who first mined salt near the brackish water of Aveiro, and brought it to Newfoundland where cod was available in massive quantities. (q.v.).Saltingwas not economically feasible until the 17th century, when cheap salt from southern Europe became available to the maritime nations of northern Europe.
Stockfish is cured in a process calledfermentationwhere cold adapted bacteria matures the fish, similar to the maturing process of cheese. Clipfish is processed in a chemical curing process called saltmaturing, similar to the maturing processes of other saltmatured products like theParma ham.
Thewater activity, aw, in a fish is defined as the ratio of thewater vapourpressure in the flesh of the fish to the vapour pressure of pure water at the same temperature and pressure. It ranges between 0 and 1, and is a parameter that measures how available the water is in the flesh of the fish. Available water is necessary for the microbial and enzymatic reactions involved in spoilage. There are a number of techniques that have been or are used to tie up the available water or remove it by reducing the aw. Traditionally, techniques such asdrying,saltingandsmokinghave been used, and have been used for thousands of years. These techniques can be very simple, for example, by using solar drying. In more recent times,freeze-drying, water bindinghumectants, and fully automated equipment with temperature and humidity control have been added. Often a combination of these techniques is used.
Salt cod has been produced for at least 500 years, since the time of the European discoveries of theNew World. Beforerefrigeration, there was a need to preserve the codfish;dryingand salting are ancient techniques to preserve nutrients and the process makes the codfish tastier.
The Portuguese tried to use this method of drying and salting on several varieties of fish from their waters, but the ideal fish came from much further north. With the "discovery" of Newfoundland in 1497, long after theBasquewhalersarrived inChannel-Port aux Basques, they started fishing its cod-richGrand Banks.  Thus,bacalhaubecame a staple of thePortuguese cuisine, nicknamedFiel amigo(faithful friend). From the 18th century, the town ofKristiansundinNorwaybecame an important place of purchasingbacalhauorklippfisk(literally "cliff fish", since the fish was dried on stone cliffs by the sea to begin with.) Since the method was introduced by the Dutchman Jappe Ippes around 1690, the town had produced klippfisk and when the Spanish merchants arrived, it became a big industry. The bacalhau or bacalao dish is sometimes said to originate from Kristiansund, where it was introduced by the Spanish and Portuguese fish buyers and became very popular. Bacalao was common food in northwest Norway to this day, as it was cheap to make. In more recent years, it has become less of an everyday staple and mostly eaten on special occasions.
This dish was also popular in Portugal and other Roman Catholic countries, because of the many days (Fridays,Lent, and other festivals) on which the Church forbade the eating of meat.Bacalhaudishes were eaten instead.