Histological Study of Ultrastructural Changes in Muscle Exposed to Various Concentrations of NaCl Brine

Efforts to reduce NaCl content in meat products hinge on gaining a deeper understanding of how NaCl content shapes product changes during the salting process. Bovine semitendinosus muscle samples were incubated for 5 days in 7 different brine baths at NaCl concentrations of 0 (control), 0.15, 0.30, 0.50, 0.75, 1.0, and 1.5 M, respectively. Histological and ultrastructural analyses showed that after incubation, muscle fiber size increased almost 30% in 0.15 and 0.3 M NaCl brine but decreased in 0.50 and 0.75 M NaCl. At above 0.75 M NaCl, brining led to significantly degraded muscle tissue, preventing the morphological characterization by image analysis. Structural modifications were strongest in samples immersed in 1 M NaCl brine. M and Z lines showed dramatic solubilization from 0.5 M NaCl upwards. Extracted proteins were released into subsarcolemmal space at 0.75 M NaCl then into extracellular space at higher NaCl levels. These findings bring insight into the sequence of structural alterations in meat as a function of ionic strength, making it possible to optimize the meat salting process.

Knowledge on the relationship between NaCl concentration, in situ structural changes and transfers of salt-extracted proteins can be usefully mobilized to reduce sodium content in cured meat products.