Influence of lightly salting and sugaring on the quality and water distribution of grass carp (Ctenopharyngodon idellus) during super-chilled storage

Low Field Nuclear Magnetic Resonance (LF-NMR) was used to evaluate the water mobility in grass carp during super-chilled storage. Grass carps were analyzed for inosine monophosphate (IMP), total viable counts, cooking loss, drip loss, biogenic amines, and sensory. Pearson's regression analysis between LF-NMR parameters and quality indicators was done to assess the feasibility of using LF-NMR to predict fish quality. Three water populations, T2b (<10 ms), T21 (20 ms-80 ms), and T22 (>100 ms), were measured. The major component T21, immobilized water, shifted to longer relaxation time with added salt and sugar due to the swelling of myofibers (P < 0.05). T21 of cooked (85 °C) flesh was lowered, indicating that immobilized water mobility decreased during heating. Curing treatments predominately accelerated IMP formation, inhibited bacterial growth, retarded cooking loss, and improved the overall sensory quality. The study also showed that the LF-NMR was capable of monitoring unsalted fish deterioration.