Rheology and interactions of whey protein isolate with galactomannans

This study examines the influence of thermal denaturation time and shear on the interactions and gelation behavior of whey protein isolate (WPI) combined with either of two plant-based galactomannans, guar gum (GG) or locust bean gum (LBG). WPI gelation at 80 °C under a shear rate of 20 s -1 produces a three-dimensional crosslinked network, with the incorporation of GG and LBG further enhancing its elastic modulus ( G' ). An optimal denaturation time of 15 min maximized gel strength for both WPI and WPI+LBG, whereas WPI+GG exhibited a high and nearly invariant G' across varying denaturation times, highlighting its robust network structure. Shear-rate dependent experiments reveal G' increases with shear rate, particularly in WPI+LBG, which formed a more interconnected bi-continuous network. Confocal imaging with fast Fourier transform (FFT) analysis indicates that GG primarily increased matrix viscosity, while LBG promotes gelation through phase separation and structural reinforcement. Temperature cycling experiments reveal irreversible structural modifications, with additional elasticity observed upon reheating. The activation energy for gelation, determined using Arrhenius-type analysis, is consistent across all systems, indicating that the fundamental gelation mechanism is unaffected by the presence of the gums. Isothermal titration calorimetry (ITC) reveals segregative interactions between WPI and the galactomannans, highlighting their role in gel reinforcement without altering protein denaturation pathways. Collectively, these findings demonstrate the synergistic potential of incorporating GG and LBG into WPI hydrogels, offering valuable insights for the design of tailored biopolymer systems in food and materials science. • Examined interactions between whey protein & galactomannans using multiprong approach • Isothermal titration calorimetry (ITC) and confocal imaging complement rheology • ITC provides thermodynamic evidence of segregation-driven protein gelation • Locust bean gum reinforces protein gels, while guar gum acts as a passive thickener • Gelation mechanism independent of temperature