Abstract:Vacuum-assisted low temperature salting was used to pickle fresh fish，and the effects of this technology were assessed by evaluating changes in water migration and tissue structure in the fish during the pickling process.Extending salting time positively correlated with NaCl content in the fish，reaching a peak value（1.48%）at 240 min.By contrast，water content in the fish showed a downward trend，reaching its lowest value（75.5%）at 280 min.When curing time reached 120 min，the relaxation time（T22）of weakly bound atmospheric water，and the relaxation time（T23）of immobilized water both reached their maximum values（P<0.05）.The corresponding relaxation peak area ratios for P22and P23were the respective minima and maxima，indicating that the degrees of freedom of bound atmospheric water and immobilized water increased，and some bound atmospheric water molecules were converted to immobilized waters.Magnetic resonance imaging results also showed that fish proton density began to increase at 120 min，then became basically unchanging after reaching a peak at 160 min.Scanning electron microscopy（SEM）showed that muscle fibers from fish tissue underwent expansion，loosening，and successive blurring from their original compact filamentous structure to their final flaky gel state.In conclusion，the changes were observed in water migration and fish tissue structure during vacuum curing correlate well with fish gelation during salting.