Multi-target cryoprotection of gelatin-tea polyphenol complexes on surimi through ice inhibition and component stabilization

In this study, the multi-cryoprotective effects of gelatin-tea polyphenol complexes were explored by ice inhibition and component stabilization. The structural properties of these gelatin-tea polyphenol complexes were characterized using Fourier transform infrared spectroscopy and X-ray diffraction analysis. The freezing behavior and antifreeze capabilities of the complexes were investigated through differential scanning calorimetry and ice recrystallization inhibition assays. Additionally, the cryoprotective effects of the complexes at various concentrations (1%, 2.5%, and 4%, m/m) on myofibrillar proteins were examined. The hydrogen bond interactions between the amino groups of gelatin and the phenolic hydroxyl groups of polyphenol facilitated the formation of complexes. The GP-5 group (the ratio of polyphenols to gelatin is 1:250) has the reduced freezing point (−1.68 ℃) and frozen water content (85.32%) compared to the control group. Notably, the addition of 2.5% (2.5G group) or 4% GP-5 (4G group) consistently demonstrated superior and stable ice-inhibition performance against various frozen conditions. GP-5 group also showed great ice recrystallization inhibition (IRI) ability with minimum size of ice crystals ranged of 125−214 μm2. Furthermore, 2.5G group and S group (commercial antifreeze agent (containing 4% sucrose and sorbitol)) had a comparable total volatile base-nitrogen (3.81, 4.34), thiobarbituric acid reactive substances assay (1.18, 1.32), sulfhydryl contents (29.52, 25.48) and Ca2+-ATP activity (0.44, 0.36). Furthermore, the 2.5G group also demonstrated significant tissue integrity against ice-induced damage, as indicated by similar fractal dimension to that of the S group. Size measurements and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis further suggested that the ice-inhibiting effects and compositional stabilization from complexes enhanced protein structure stability. This is the first study to make gelatin-tea polyphenol composite microgels to protect surimi from freezing. Thereafter, the dual cryoprotective roles of microgels for surimi provide some inspiring references for the development of the desired antifreeze.