23Na-MRI quantification of sodium and water mobility in pork during brine curing

A model study on movements of sodium ions in pork loin during brining was carried out using 23Na-magnetic resonance imaging (23Na-MRI). Samples of different pH and post-mortem age were mounted in Plexiglas® cylinders with built-in phantoms and cured in 18.9% and 18.1% NaCl (w/v), respectively. One-dimensional 23Na-MRI and apparent diffusion coefficient (ADC) profiles were obtained over 5 days with intervals of 24 h. On day 5 the meat was cut into 1 cm slices and analyzed for chloride content. 23Na-MRI and ADC profiles of meat provided detailed non-destructive information about salt and water movements during brine curing. Quantification of salt concentration in meat by one-dimensional 23Na-MRI profiling proved successful at values above 0.9 g NaCl/100 g sample in the meat. 23Na measurements were calibrated against chemically determined chloride, yielding a linear relationship. 23Na-MRI profiles suggested that the diffusion of salt into whole meat cuts cannot be described by simple ordinary Fickian diffusion with a constant diffusion coefficient. The diffusion coefficient is suggested to be affected by changes in NaCl concentration, swelling and degree of dehydration.