Estimation of NaCl diffusivity by computed tomography in the Semimembranosus muscle during salting of fresh and frozen/thawed hams

In the elaboration of dry-cured hams, the understanding of salt diffusion is an important step to optimise salt uptake. Calibrated computed tomography (CT) gives non-destructive measurements of salt and water contents. The aim of this study is to develop a simplified methodology based on an unidirectional diffusion model and CT measurements for assessing salt diffusion in Semimembranosus muscle (SM) during salting of ham. Five pork carcasses were selected according to the SM muscle pH (5.8 ± 0.1), 24 h post mortem, and hams weight (12.7 ± 0.5 kg). One ham from each pair was subjected to a freezing/thawing treatment before salting period. CT images of a central section were taken in each ham during the 16 days of the salting period. From each voxel, NaCl and moisture mass fractions were determined and introduced in the diffusion model. Thus, NaCl apparent diffusion coefficients were calculated for each ham. Resulting diffusion coefficients are in the same order of magnitude than values given by literature. As expected, 30% higher diffusion coefficients were found for frozen/thawed hams samples. Combination of calibrated CT measurements with a simple diffusion model can be used to obtain a non-destructive estimation NaCl apparent diffusivity during dry-curing of ham.

► A non-destructive method to estimate salt diffusion in ham is proposed. ► The method combines CT images with an unidirectional diffusivity model. ► The effect of frozen/thawed ham on salt diffusion during salting is studied. ► The method confirms a positive effect of frozen/thawed ham on salt diffusion.