Effect of water-retention agents on Scomberomorus niphonius surimi after repeated freeze-thaw cycles: low-field NMR and MRI studies

Repeated freeze-thaw cycles can directly cause the changes in the water distribution, physicochemical characteristics, and microstructure of Scomberomorus niphonius surimi. To improve the quality of S. niphonius surimi, the effect of water retention agents (phosphate and trehalose) was investigated during freeze-thaw cycles. The results of low-field nuclear magnetic resonance (LF-NMR) combined with magnetic resonance imaging (MRI) analysis showed that the water retention agents could obviously decrease the water loss and water mobility during repeated freeze-thaw cycles. Water retention agent significantly reduced the cook loss and improved the surimi quality by decreasing the surimi protein denaturation. The scanning electron microscopy (SEM) characterization revealed that water retention agents could obviously ameliorate the protein structure damage. In addition, the principal component analysis combined with LF-NMR parameters showed clear discrimination between samples supplemented with different water retention agents. In a word, the LF-NMR and MRI might provide useful information in a non-invasive manner for monitoring the effects of water-retention agents on surimi after repeated freeze-thaw cycles.