processes: evaporation from the surface and the diffusion of water and solutes (salt, sugars, etc.) in the internal fractions.
The diffusion ratio of the solutes and water depends directly on temperature value and on the characteristics of the product (pH, the Aw of the various fractions, the fat/lean ratio etc.), whereas evaporation is linked to the characteristics of the air (relative humidity, temperature, ventilation) (22) and to the permeability of the casing (11).
The drying of the external fractions determines the diffusion of the salt toward the inside and the migration of the water toward the outside; because the evaporation ratio is generally greater than that of diffusion, a concentration gradient is created and the salami becomes a system consisting of concentric fractions, differing as to quantities of salt and water (23,24).
Excessive drying of the external fractions may give rise to surface proteinic denatura-tion with aesthetic (''drying rim'') or functional damage with reduced permeability of the surface fractions (25).
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