On the face of it, curing hams is a simple process. All you need is salt, air and time. The process starts in conditions of low temperature and high humidity, and gradually the temperature is raised and the humidity lowered. It is a natural, spontaneous, ongoing transformation that has four distinct production stages:
. After the pigs are sacrificed, the freshly cut hams are covered with sea salt for a week or ten days, depending on weight. The rule of thumb is 1 day per two pounds of meat. The salting room is kept between 0 - 3°C at 85-95% humidity. After this period, the hams are rinsed in lukewarm water to remove salt crystals from the surface.
. Once cleansed of surface salt, the hams are kept for one to two months in cold rooms at a temperature between 3° and 6° C and a relative humidity of 80 or 90%. During this resting period the salt penetrates the pieces thoroughly, enhancing dehydration and conservation. This process gives hams a significantly denser consistency, since much water has been removed.
. During this period, hams are moved to a "secadero", or natural drying area, where temperature and humidity are controlled through ventilation. Temperature ranges from 15° to 30° C for the 6 to 9 month drying period, during which hams continue to lose moisture, and "sweating" - dissemination of fat throughout the muscle fibers, which then retain the aroma they have acquired - also occurs. The final flavor and aromas begin to develop during this stage, due to a series of changes that occur in the protein and fat of these hams. (This is usually the final stage in processing a Serrano ham.)
Unlike prosciutto or Parma ham, the curing ham is not covered by lard or any other external ingredient that would affect the flavor. It is pure ham, waiting to be improved by the mountain air. At the right time, determined by the ham master who inspects each ham, the Ibérico hams are transferred to the bodega where they hang from a cord for as much time as it will take to finish the cure and produce the best product.
. Ibérico hams are then hung in cellars, or bodegas, for up to a maximum of 30 months. Temperature may range between 10° and 20° C, and relative humidity, between 60 and 80%. During this phase, hams continue to undergo the biochemical processes initiated during the curing process, enhanced by microbial flora, which give them their particular aroma and final flavor.
Usually the Jamón Ibéricos take at least two years to reach their peak of flavor - some of the best ones the ham master will cure for another half a year, or more.
Part of his decision is based upon weight - the larger hams will take a longer time to cure, the other factor in his decision is an art.
Determining the time when the Jamón Ibérico is ready is the responsibility of a specialist who draws on years of experience. He inserts a thin sliver of bone into the interior of the curing ham, and by sight and aroma makes his decision. It is similar to a baker inserting toothpick into a baking cake to see if it is done - except the stakes are vastly higher, since this meat is so precious.