The Effect of Ice-Binding Protein from Leucosporidium sp. AY30 (LeIBP) on the Physicochemical Quality and Microstructure of Largemouth Bass During Freeze–Thaw Cycles

This study investigated the effect of various concentrations (0.01%, 0.05%, 0.1%, 0.2%, 0.5%) of ice-binding protein from <i>Leucosporidium</i> sp. AY30 (LeIBP) on the freezing efficiency, microstructure, and physicochemical quality of largemouth bass during freeze-thaw cycles and demonstrated the optimal addition conditions of LeIBP. This study found that LeIBP could effectively lower the freezing point of fish without altering the phase transition time significantly. LeIBP can significantly reduce the cross-sectional area and diameter of ice crystals and inhibit recrystallization. LeIBP was found to maintain the stability of protein secondary structure and prevented protein denaturation by increasing the proportion of α-helix. The inclusion of LeIBP retained the water-holding capacity of fish effectively. Furthermore, LeIBP treatment could partially prevent the degradation of fish meat texture. The lightness and whiteness values of fish treated with LeIBP were increased, while the redness and yellowness values were decreased. At the end of freeze-thaw cycle, the LeIBP-treated group presented pH values similar to fresh fish. Overall, 0.05% LeIBP was observed to be the most effective concentration to inhibit ice crystal growth, thereby maintaining the quality of the fish.