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In this study, cold-set large yellow croaker (Pseudosciaena crocea) roe protein isolate (pcRPI) gels were prepared by glucono-δ-lactone (GDL) at different concentrations. The 0.1% and 0.2% GDL induced pcRPI at 50 mg/mL to form cold-set gels, while pcRPI suspension with 0.4% GDL addition still showed a fluid state. The pcRPI gel induced by 0.2% GDL showed better rheological properties and its G' value was about 5.1 times than that of 0.1% GDL. In addition, pcRPI gels induced by 0.1% and 0.2% GDL showed similar water holding capacity, and 0.2% GDL-induced pcRPI gels showed a special T 2 peak in 2249.0 ms which might represent free water on the surface of the gel. Furthermore, the higher total number of junctions, vessels percentage area, and lower lacunarity indicated a denser three-dimensional network structure in pcRPI gels induced by 0.1% and 0.2% GDL. Particle size tests and AFM results further confirmed that GDL induced pcRPI to form cold-set gels by promoting the formation of protein aggregates. Therefore, 0.1–0.2% GDL are suitable to prepare pcRPI cold-set gels. These results may deepen the understanding on cold-set pcRPI gels induced by GDL. • Pseudosciaena crocea roe protein isolates (pcRPI) had potential to form cold-set gels. • 0.2% glucono-δ-lactone (GDL)-induced pcRPI gels showed good rheological properties. • The 0.1–0.2% GDL induced pcRPI gels had a dense three-dimensional network structure. • GDL-induced pcRPI gels were promoted by the formation of protein aggregates. [ABSTRACT FROM AUTHOR]

Roes are the main byproducts during the processing of large yellow croaker (Pseudosciaena crocea) and have not been well utilized. Heat-induced gels were prepared by using P. crocea roe protein isolates (pcRPI), and the influence of pH on the gel properties was also investigated. pcRPI could not form a gel at pH 4–6 but showed gelation behaviors at pH 7–9. The pcRPI gels prepared at pH 8 had a lower gel point (84 °C), and their G ′ reached 535.4 Pa. Moreover, pcRPI gels formed at pH 8–9 had a more continuous network structure with a shorter T 2 relaxation time than those at other pH conditions. Additionally, vitellogenin and vitellogenin B and C in pcRPI easily formed protein complexes during heating. The hydrophobic interactions, which were the main force between protein molecules during heating, as shown by molecular dynamics simulation, also contributed to gel formation. pcRPI has the potential to be used as a novel hydrogel product in food and other fields. • The optimum pH of P. crocea roe protein isolates (pcRPI) to form gels was pH 8. • The water holding ability of pcRPI gels was enhanced as pH increased. • The pcRPI gels had smoother surface and continuous network structure at pH 8–9. • Hydrophobic interactions were the main forces in the formation of pcRPI gels. [ABSTRACT FROM AUTHOR]