Abstract: In order to investigate the effect of salt concentration on the structure and quality of grass carp muscle during wet pickling, the effects of salt concentration on the protein, water, fat, muscle tissue structure and texture of grass carp muscle during wet pickling were studied, and analyzed by centrifugal loss rate, thiobarbituric reactive substances (TBARs), dodecyl sulfate Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier infrared and low-field nuclear magnetic resonance. Our results showed that: 1) the crude protein content of grass carp decreased by 2%, the centrifugal loss rate decreased by 8%, and the TBARs value increased by 2 times when salt concentration increased from 3% to 12%. 2) Based on the low-field nuclear magnetic resonance analysis data, it was found that the bound water and free water in the fish tissue were converted into non-flowable water with the increasing of the salt concentration. 3) The second-derivative infrared spectrum results showed that the peak intensity of 1747 cm-1 significantly reduced after pickling, and the peak intensity ranging between 1612-1698 cm-1 and 1523-1553 cm-1 significantly increased at asalt concentration of 3%. The peak intensity gradually decreased with the increasing of salt concentration. 4) SEM and TEM results showed that the muscle fibers of fish meat became blurred at 3% salt concentration, but the sarcoplasmic tissue remained intact. The morphology of sarcoplasma became loose at 12% salt concentration. 5) 12% salt concentration would destroy the spatial structure of fish protein, thus making fish tissue loose, increasing water loss, and reducing the edible quality of fish meat. However, 3% salt concentration had the smallest effects on fish meat texture. Our study can provide scientific basis for the development of high quality and convenient aquatic products in the future.

Key words: wet pickling, salt concentration, grass carp, quality, muscle tissue, texture