a. Hams The salted hams are placed in suitable rooms (salting rooms) to allow for the diffusion of salt in conditions (low temperature) that prevent anomalous microbial growth.
The forming of a saturated solution on the surface of hams is an indispensable condition for the correct diffusion of salt to the more internal fractions (5). The thermohygrometric parameter values should be chosen on the basis of sure scientific ground (e.g. minimum growth temperature, in the pH, and Aw conditions, of the internal fractions, of a reference pathogenic microbe (e.g., type B Cl.botulinum). The technologies currently employed are essentially different on account of the thermohygrometric values (temperature and relative humidity) and the modality of storage of the products in the salting rooms.
The salted hams are placed in open containers of varying dimensions, arranged in heaps completely covered in salt or placed individually on shelving or similar supports; the latter technique is the only one adopted for hams partially covered in salt (1,6,7). In the first two cases, only one small fraction of the hams is in direct contact with the air, and the diffusion of the salt and water essentially depends on the characteristics of the salt and ham and on the temperature. In the latter case, these processes also depend on relative Humidity; values near to those of the Aw of the saturated salt solution (Aw = 0.75) ensure a good outcome of the process; the optima choice of the control parameters depends in any case on the type of product and conditioning plant.
In many technologies, the salting stage is subdivided into two or more substages. At the end of every substage, the residual salt can be removed and replaced with clean salt, and the hams can be submitted to mechanical massage (manually or with the aid of appropriate machines) to facilitate the removal of any blood still present in the main blood vessels.
The overall duration of the salting stage depends directly on the quantity of salt desired in the finished product and on the diffusion rate, ranging from a few days (for small products completely covered in salt) to several weeks (Parma ham). The differences that are noted in the more traditional products (jamon iberico, Parma ham), and that have similar quantities of salt in the finished product, depend on the differing quantities added at the salting stage, the different modalities of trimming, and the thermohygrometric conditions (8).
Independent of relative humidity values, the preestablished temperatures take into account the need to control microbial growth and to ensure the appropriate diffusion of salt and water, varying within wide limits—for example 36-40°F (9), 1-3°C (10), 2-3°C (2), 0.5-4.0°C (11).
b. Other Products For other products, similar storage techniques are used. If the products are left in tumblers, or are deposited in impermeable containers, the salt absorbs water from the surface fractions and forms a saturated brine; the quantity of brine depends directly on the quantity of salt and of lean meat in contact with the salt; generally, it is not sufficient to cover completely all the product. This may give rise to an uneven production, rectifiable by means of operations (tumbling, changing the loading of the product into the containers, etc.) that allow for a more uniform treatment.
The salting time depends on the quantity of salt and other additives or ingredients to be absorbed (the various ingredients and additives have varying diffusion coefficients) (12); because the processes are slow, the salting period may also be long (e.g., 3-4 weeks for beef products with a heavy weight). During salting, the quantity and concentration of brine diminish with the passing of the days, and the Aw and surface microbial population increase.
c. Brining The addition of salt may also be by immersion or by the injection of brines of different concentrations; in this second case, the microbiological and physicochemical conditions of the internal fractions are also modified to a significant degree, and the salting techniques must also be modified in order to optimize the growth of the characteristic microorganisms present and/or starter cultures (13).
d. Desalting In some countries, prolonged salting is followed by a desalting stage, during which the products are placed in water, sometimes running, for a certain period (more or less one day).
This technique speeds up the salt diffusion by increasing the concentration of the external fractions, and facilitates quality control of the finished product, eliminating a part of the salt absorbed. The necessity to purify large volumes of contaminated water and an increase in the quantity of moisture in the surface fractions are the most obvious limitations of this technique, which in many countries is not accepted.
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