Tea polyphenol-loaded chitosan/pectin nanoparticle as a nucleating agent for slurry ice production and its application in preservation of large yellow croaker (Pseudosciaena crocea).

Slurry ice preparation experiences considerable supercooling, which can be mitigated by nano-nucleating agents. A nano-nucleating agent (CH/PE-TP NPs) was prepared by ultrasonication-assistant self-assembly of chitosan (CH) and pectin (PE), encapsulated with tea polyphenols (TP). Ultrasonication for 10 min downsized self-assembled aggregates from 5.4 μm to approximately 500 nm and improved the dispersion of NPs. Optimal encapsulation efficiency was achieved with a CH/PE ratio of 1:5 (v/v), pH 5.0 and a TP concentration of 0.8 mg/mL. FTIR analysis indicated CH and PE encapsulated TP through electrostatic interaction between amino and carboxyl groups. Furthermore, the spherical shape of NPs was captured by electron microscopy. The addition of CH/PE-TP NPs (simulated seawater/NPs 4:6, v/v) for slurry ice production led to a reduction in supercooling by 8.3 °C and decreased energy consumption by 24.8 %. Notably, the CH/PE-TP NPs could be reused by refreezing the melted water of slurry ice. Total volatile basic nitrogen, pH, thiobarbituric acid reactive substances and total viable bacteria count demonstrated that CH/PE-TP NPs-based slurry ice was more effective than flake ice and conventional slurry ice in preserving large yellow croaker. In summary, CH/PE-TP NPs as nucleating agent effectively reduce energy consumption and extend the shelf life of aquatic products.