Abstract: In order to investigate the effect of salt concentration on the texture, microstructure and quality of wet-cured grass carp muscle, we studied changes in the centrifugal loss, thiobarbituric acid reactive substances (TBARS), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern, scanning electron microscopic (SEM) image, transmission electron microscopic (TEM) image, Fourier transform infrared (FT-IR) spectrum and low-field nuclear magnetic resonance (LF-NMR) spectrum of cured fish samples as a function of salt concentration. Also, we monitored the protein, moisture and fat contents, microstructure and texture. Our results showed that the crude protein content decreased by 2%, the centrifugal loss rate decreased by 8%, and the TBARS value increased about twice when salt concentration increased from 30 to 120 mg/mL. NMR data revealed that bound water and free water were converted into non-flowable water with increasing salt concentration. The second-derivative infrared spectrum showed that the intensity of the 1 747 cm-1 peak was significantly reduced after curing, and the intensity of the peaks in the ranges of 1 612–1 698 cm-1 and 1 523–1 553 cm-1 was significantly increased at a salt concentration of 30 mg/mL. The peak intensity gradually decreased with increasing salt concentration. SEM and TEM results showed that fish muscle fibers became blurred at 30 mg/mL salt concentration, while the sarcoplasmic tissue remained intact. The morphology of sarcoplasma became loose at 120 mg/mL salt concentration, and the spatial structure of fish protein was destroyed, thus making fish muscle tissue loose, increasing water loss, and reducing the eating quality of fish meat. However, 30 mg/mL salt concentration had the smallest effects on fish muscle texture. Our study can provide a scientific basis for the development of high-quality ready-to-eat aquatic products in the future.

Key words: wet curing; salt concentration; grass carp; quality; muscle tissue; texture