Dry cured-ham microestructure: A T2 NMR relaxometry, SEM and uniaxial tensile test combined study

NMR relaxation analyses were performed on dry-cured hams at different processing times to evaluate the ranges of variation of H-1 transverse relaxation time (T-2) in representative ham muscle tissues, due to dehydration and salt uptake. Changes in the mobility and distribution of water and fat marbling were detected throughout ripening. Three to four different H-1 populations were identified: T-2b, T-21, T-22 and T-2'. The shift of the main population, T-21, toward faster relaxation times indicates a higher degree of immobilization of water, and the change is related to the increase in the consistency of the meat matrix. NMR results, supported by SEM images, suggest that ripening favors the compaction of ham structure and leads to a high organized myofibrilar matrix in which the remaining water is trapped within the protein tridimensional network. A new T-2 signal, T2', was observed at the last maturation stages linked to protons related to the fat phase which is detected due to the fat redistribution in the dehydrated matrix. The main water population, T-21 showed a positive linear relationship with water content and it was negative related with the breaking strength. Consequently, the study demonstrated that NMR T-2 relaxometry is a promising technique to elucidate associations between the biophysical state of intrinsic water and progression in processing of dry-cured ham.