Abstract: The study investigated the effect of the ice-binding protein from Leucosporidium sp. AY30 (LeIBP) expressed in food-grade Aspergillus niger on the physicochemical quality and microstructure of frozen largemouth bass fillets. The freezing point, supercooling degree, and thermal hysteresis activity (THA) of LeIBP solutions with mass fractions ranging from 0% to 0.5% were measured. The effects of the LeIBP solutions on the ice crystal morphology, protein secondary structure, water-holding capacity, pH, color difference, and texture properties of frozen fish muscle were analyzed to determine the optimal concentration of LeIBP for preserving the quality of frozen fish. The results showed that the freezing point of the LeIBP solutions ranged from −1.26 to −1.47 ℃, the supercooling degree was 5.04 to 7.07 ℃, and the THA was 1.25 to 1.49 ℃. Compared with the control group, the addition of LeIBP effectively inhibited recrystallization, reducing the cross-sectional area of ice crystals by 5.62% to 95.57% and the equivalent average diameter by 0.07% to 78.74%, while maintaining the stability of protein secondary structure by increasing the α-helix content. Additionally, the addition of LeIBP reduced the thawing loss of fish muscle by 1.65% to 4.38%, decrease the pH by 0.06 to 0.29, and effectively maintained the color difference and texture. Therefore, LeIBP addition could significantly slow down the quality deterioration of largemouth bass muscle during the freezing process, with the best cryoprotective effect observed at a concentration of 0.05%.

Key words: ice-binding protein from Leucosporidium sp. AY30; frozen storage; largemouth bass; microstructure; physicochemical quality