Water and Salt Distribution in Atlantic Salmon (Salmo salar) Studied by Low-Field ¹H NMR, ¹H and ²³Na MRI and Light Microscopy: Effects of Raw Material Quality and Brine Salting

Abstract

The effect of different Atlantic salmon raw materials (prerigor, postrigor and frozen/thawed) on water mobility and salt uptake after brine salting was investigated by using LF 1H NMR T2 relaxation,1H and 23Na MRI and light microscopy. Distributed exponential analysis of the T2 relaxation data revealed two main water pools in all raw materials, T21 and T22, with relaxation times in the range of 20-100 ms and 100-300 ms, respectively. Raw material differences were reflected in the T2 relaxation data. Light microscopy demonstrated structural differences between unsalted and salted raw materials. For prerigor fillets, salting induced a decrease in T21 population coupled with a more open microstructure compared to unsalted fillets, whereas for frozen/thawed fillets, an increase in T21 population coupled with salt-induced swelling of myofibers was observed. The result implies that the T21 population was directly affected by the density of the muscle myofiber lattice. MR imaging revealed significant differences in salt uptake between raw materials, prerigor salted fillets gained least salt (1.3-1.6% NaCl), whereas the frozen/thawed fillets gained most salt (2.7-2.9% NaCl), and obtained the most even salt distribution due to the more open microstructure. This study demonstrates the advantage of LF NMR T2 relaxation and 1H and 23Na MRI as effective tools for understanding of the relationship between the microstructure of fish muscle, its water mobility and its salt uptake.

Injection of fish protein solutions of fresh saithe (Pollachius virens) fillets studied by low field Nuclear Magnetic Resonance and physicochemical measurements

“…Most studies report 2-3 water populations in fish and meat muscle, depending on their proton relaxation properties (Jepsen et al 1999;Erikson et al 2004;Bertram and Andersen 2007;Bertram et al 2009;Aursand et al 2009). Bertram and Andersen (2007) and Bertram et al (2009) identified three water populations in pork at 1-3 ms (T 2B ), suggested to correspond to water closely associated with macromolecules and proteins, at 40-80 ms (T 21 ), suggested to correspond to myofibrillar water or water located within organized protein structures and at 200-400 ms (T 22 ) corresponding to extra-myofibrillar water.…”

“…Transversal relaxation time measurement have shown to give strong correlations to various physicochemical properties of fish and meat muscle, such as moisture content (Andersen and Rinnan 2002), water holding capacities and drip loss (Jepsen et al 1999;Erikson et al 2004) and has been used to indicate pH-induced structural changes occurring in the muscle post mortem (Bertram et al 2000) as well as the effects of frozen storage on protein denaturation in fish (Steen and Lambelet 1997). The technique can give valuable information about the distribution of water throughout the muscle and how it is changed by various handling or processing (Jepsen et al 1999;Erikson et al 2004;Bertram and Andersen 2007;Bertram et al 2009;Aursand et al 2009) and is therefore an excellent technique for studies on the effects of protein injection to fish muscle.…”

Quality of Atlantic Cod Frozen in Cell Alive System, Air-Blast, and Cold Storage Freezers

“…If, for example, changes in muscle tissues would occur as a result of fish processing, this can be detected as changes in proton relaxation times (Erikson et al, 2004). A correlation between NMR relaxation times and light microscopy of salmon muscle has been described by Aursand et al (2009).…”

Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in Fossil Vertebrates Part I: Reptiles—the taphonomy of the bipedal dinosaurs Compsognathus longipes and Juravenator starki from the Solnhofen Archipelago (Jurassic, Germany)

“…On the other hand, the extent of physical activity and psychological stress before the onset of death, and the cause of death itself, can also have an effect on the point in time of the onset, dissipation and intensity of rigor mortis (Dix and Graham 2000;Krompecher et al 1983;Perper 2006;Tornberg 1996). An increased strain on the muscles antemortem (whether illness or stress related, and whether in direct relation or without any relation to the cause of death) can, for example, accelerate the onset of rigor mortis (Aursand et al 2009;Clark et al 1997;Gill-King 1997;Kiessling et al 2006;Krompecher et al 1983;Robinson et al 1953;Roth et al 2006;Tornberg 1996).…”