Modulation of Cod Myofibrillar Protein Gels by Egg White and Whey Proteins: From Aggregation Kinetics to Gel Mechanics.

In this study, we evaluated how varying concentrations of two exogenous proteins, egg white protein (EWP) and whey protein isolate (WPI) influence heat-induced aggregation and gelation of cod myofibrillar proteins (MPs). Addition of exogenous proteins enhanced the MP solubility and surface hydrophobicity while reducing the turbidity and total sulfhydryl levels. These physicochemical changes occurred during heating in three kinetic phases, an initial rapid phase (0-30 min), a slower transitional phase (30-60 min), and a second rapid aggregation phase (70-90 min) until equilibrium was reached. Dynamic rheology revealed that EWP enhanced G' at moderate concentrations but reduced it at higher levels, while WPI caused a progressive decline in G' with increasing concentration. Gel property analysis showed that EWP-M (MP:EWP = 2:14) produced the highest gel strength, whereas WPI-L (MP:WPI = 1:15) resulted in the lowest cooking loss and highest water-holding capacity (WHC). WPI-containing systems exhibited slightly lower gel strength but showed improved water retention and a uniform microstructure. Notably, a 1:1 EWP-WPI combination showed synergistic network solubility, hydrophobic exposure, and uniform microstructure, leading to high gel strength with minimal cooking loss and maximum WHC. Mechanistically, EWP acted as a structural enhancer, promoting gel network strengthening and increased rigidity, whereas WPI functioned primarily as a filler, enhancing water retention and reducing structural heterogeneity. These findings offer key insights into MP/EWP-WPI interactions and support the optimization of composite protein gel systems.