Water properties and salt uptake in Atlantic salmon fillets as affected by ante-mortem stress, rigor mortis, and brine salting: A low-field 1H NMR and 1H/23Na MRI study

A low-field (LF) 1H NMR T2 relaxation and 23Na/1H MRI study was performed on Atlantic salmon to study the effect of ante-mortem handling stress and rigor mortis on muscle water properties and subsequent post-rigor salting. Compared to rested fish, exhausted fish exhibited a more rapid and stronger development of rigor mortis. This resulted in significant differences in post-rigor water-holding capacity and salt uptake. By LF NMR T2 relaxation analysis significant differences in water distribution according to (1) ante-mortem handling, (2) fillet location, and (3) brine salting were detected. Furthermore, 23Na MRI revealed differences between the two treatments in fillet salt distribution, where the salt penetration in exhausted fillets was more pronounced. By combining 1H and 23Na MR images, the salt diffusion and distribution seemed to be highly affected by the distribution of fat.