The ability of protein micro-phase separation and proteinepolysaccharide segregative phase separation
to generate a range of gel structures and textures was evaluated. Whey protein isolate/k-carrageenan
mixed gels were prepared with 13% (w/v) whey protein isolate, 0e0.6% (w/w) k-carrageenan and 50, 100
or 250 mM NaCl. The microstructure of gels, determined by confocal laser scanning microscopy, varied
from homogenous to protein continuous, bicontinuous, coarse stranded or k-carrageenan continuous,
depending on the k-carrageenan concentration. Microstructure also varied from stranded to particulate
(micro-phase separated) depending on the salt concentration. The rheological behavior of mixed gels
corresponded to the shift in the continuous phase from protein to k-carrageenan. At small concentrations
of k-carrageenan, where carrageenan-rich droplets were dispersed in a continuous protein-rich matrix,
gel strength (fracture stress) and firmness (G0
) increased due to increased local concentration of proteins
caused by phase separation. At higher k-carrageenan concentrations, gels were substantially less firm,
weaker and less deformable (fracture strain). The change in the continuous phase from protein
continuous to carrageenan continuous explained the major change in mechanical properties and waterholding
properties. The shift in microstructure occurred at lower concentrations of k-carrageenan when
whey proteins were under micro-phase separation conditions. The results demonstrated how the
combined mechanisms of ion-induced micro-phase separation of proteins and proteinepolysaccharide
phase separation and inversion can be used to alter gel structure and texture.