A comparison of the gelling and foaming properties of whey and egg proteins

Abstract

Whey and egg white protein ingredients are often used in similar functional applications, which involve gelation or foam formation. This chapter compares the large-strain (fracture) rheological properties of heat-induced (80°C for 30 min) whey protein isolate (WPI) and egg white (EW) gels made under solution conditions, which are optimized for gel strength (fracture stress). Gels formed under these conditions had similar values for fracture stress over the range of 6–18% w/v protein. Gel deformability (fracture strain), had protein-specific trends. Fracture strain for WPI gels decreases as protein concentration increases, whereas fracture strain for EW gels remains constant. The stress–strain relationships for EW and WPI gels are characterized by calculating a ratio between the rigidity (stress/strain) at fracture and the rigidity at 30% of the fracture strain, called the rigidity ratio. Both EW and WPI gels have higher rigidity ratios (1.4–1.8) at low protein concentrations then shift to lower values, of around 1, as protein concentration increases. The various gels formed at different protein concentrations and heating times and temperatures could be fit to a master curve of rigidity ratio vs. fracture rigidity. The yield stress of EW and WPI foams is determined by a vane method. Egg white foams exhibit relatively high yield stresses, even at low protein concentration and short whipping time. Maximum yield stress occur at 8–10 min in egg white foams, while whey protein isolate foams require >15 min. The rheological properties of egg white and whey protein isolate foams and gels show protein-specific and protein-independent properties.