Cod from the cold waters of the North Atlantic was one of Europe's major foods for several centuries. Salted and dried on the shores of Newfoundland or Norway, salt cod was traded all across Europe for trade goods including salt for the next year's fishery. Although the cod are now sadly diminished from their former numbers, salt cod remains a popular food in many parts of the world. The heavily salted fish resists spoilage but still requires a modest degree of scrutiny before it is cooked.
Examine the salt cod for signs that it has come into contact with moisture. Salt cod will keep for years if properly stored, but moisture makes it vulnerable to spoilage and fermentation. Any soft or blotchy areas on the flesh, or any discolouration, usually indicates damage from moisture.
Check the colour of the cod. Properly cured cod should remain white or ivory in colour, even after long-term storage. If the cod has developed a yellow or red hue, it has become oxidised or been affected by microorganisms. Discoloured salt cod should be discarded.
Smell the cod. Properly cured salt cod will have a strong smell of fish and brine, but the odour is not unpleasant. Any mouldy, fermented or vinegary smells indicate spoilage, and the fish should be discarded.
Soak the cod overnight in cold water, to begin rehydrating it. Drain the water, and once again check for soft or discoloured spots and unpleasant aromas. If no signs of spoilage are detected on the dried or soaked fish, it should be safe to use.
Buy your salt cod in large pieces, rather than small, whenever possible. Larger pieces have less exposure to oxygen, and oxidation in salt fish detracts from flavour. When looking for salt cod recipes, don't limit yourself to New England. Italy, Spain, France, Portugal and the Caribbean each have a varied repertoire of salt cod dishes.