Moisture diffusivity in the lean tissue of dry-cured ham at different process times

The aim of this study was to determine the effective moisture diffusivity coefficient (D(e)) during dry-cured ham processing in two muscles, an internal one (Biceps femoris, BF) and an external one (Semimembranosus, SM), at different temperatures. Two adjacent samples, which included both SM and BF muscles, were selected after salting (PS), after resting (PR), after 4 months of drying (D1) and at the end of the process (D2). One was used to determine the initial profiles of moisture and NaCl/moisture and the other to determine D(e) at different temperatures (1 and 5°C in PS; 5 and 12°C in PR; 12, 19 and 26°C in D1; 19 and 33°C in D2). D(e) was higher in the muscle with the higher moisture content (BF) except in PS and PR, where a gradient of NaCl/moisture ratio was observed in SM muscle. There was a positive effect of temperature on D(e), but it decreased during processing of the dry-cured ham. A simple diffusive model, with a unique and constant moisture diffusivity coefficient or with a coefficient depending only on temperature, does not explain the whole drying process correctly. The effects of moisture content and the gradient of NaCl/moisture ratio on D(e) have to be considered.