Phase behavior and synergistic gelation of scallop (Patinopecten yessoensis) male gonad hydrolysates and gellan gum driven by pH.

Background: Previous studies have investigated complexation and coacervation of scallop Patinopecten yessoensis male gonad hydrolysates (SMGHs) and polysaccharides influenced by pH and blending ratio. It has been found that SMGHs/polysaccharide composite shows better gel properties under strongly acidic conditions. Thus, the complexation and coacervation of SMGHs and gellan gum (GG) were investigated via turbidimetric titration at different pH values (1-12) and biopolymer blending ratios (9.5:0.5-6:4).

Results: Both pH_c and pH_φ1 exhibited ratio-independent behavior with constant values at approximately pH 5.8 and pH 3.8, respectively, dividing SMGHs/GG blends into three phases named mixed polymers, soluble complexes and insoluble coacervates, respectively. Overall, SMGHs and GG exhibited synergistic gelation under neutral and acidic conditions, with the initial storage modulus (G') increasing by approximately 42.5-, 573.7- and 3421-fold and 97.7-, 550.3- and 0.5-fold, respectively, at pH 7, 5 and 3, compared with SMGHs and GG. As pH decreased from 7 to 3, the initial G' and viscosity η values of SMGHs/GG gels increased by 20.1- and 2.3-fold, respectively, exhibiting the greatest increase in gel strength. Moreover, the free water in the SMGHs/GG system significantly shifted toward lower relaxation times attributed to the immobilization of the outer hydration layers. SMGHs/GG gels in the insoluble phase exhibited denser networks and rougher surfaces, supporting the enhanced rheological properties and water retention capacity of the gel.

Conclusion: This work provides a basic foundation for the development of pH-driven SMGHs/GG gelation by examining complexation and coacervation processes. © 2024 Society of Chemical Industry.