Effects of ice-binding protein from Leucosporidium sp. AY30 (LeIBP) on physicochemical quality, myofibrillar protein and ice crystal morphology of largemouth bass during air freezing

This study investigated the freezing characteristics of Arctic yeast Leucosporidium sp. AY30 ice-binding protein (LeIBP) after heterologous expression by Aspergillus niger at different concentrations (0.01 %, 0.05 %, 0.1 %, 0.2 %, 0.5 %) and elucidated its effects on physicochemical quality, myofibrillar protein (MP) and ice crystal morphology of largemouth bass during air freezing. LeIBP achieved ice crystal regulation by significantly reducing the freezing point, super-cooling degree and phase transition time of the aqueous solution and prolonging the time of the maximum ice crystal formation zone (−1 to −5 °C). Its thermal hysteresis activity (THA) reached a peak at 0.2 % concentration (1.36 °C), which was superior to the THA of most traditional AFPs. Notably, the addition of 0.05 %LeIBP dramatically reduced the cross-sectional area and mean diameter of ice crystals by up to 91 % and 70 %, respectively. In addition, the addition of LeIBP better maintained the texture of fish, led to an increase in the L* value and a decrease in the b* value, and inhibited the decrease in the a* value, but decreased its water holding capacity slightly. Meanwhile, the addition of 0.01 %LeIBP better inhibited the reduction of MP content and maintained the stability of MP tertiary structure. The addition of LeIBP increased the α-helix content by 1.0–6.9 % to maintain the MP secondary structure, also significantly increased the ion bond content, hydrogen bond content, and hydrophobic interactions. In summary, the addition of low concentration (0.01 % and 0.05 %) of LeIBP better maintained the quality of fish meat during air freezing.