Cold-set whey protein gels induced by calcium or sodium salt addition

Cold-set whey protein isolate (WPI) gels formed by sodium or calcium chloride diffusion through dialysis membranes were evaluated by mechanical properties, water-holding capacity and microscopy. The increase of WPI concentration led to a decrease of porosity of the gels and to an increase of hardness, elasticity and water-holding capacity for both systems (CaCl₂ and NaCl). WPI gels formed by calcium chloride addition were harder, more elastic and opaque, but less deformable and with decreased ability to hold water in relation to sodium gels. The non linear part of stress-strain data was evaluated by the Blatz, Sharda, and Tschoegl equation and cold-set gels induced by calcium and sodium chloride addition showed strain-weakening and strain-hardening behaviour, respectively. The fractal structure of the gels indicated a weak-link behaviour. For WPI gels results suggest intrafloc links, formed at heating step, which were more rigid than the interfloc links, promoted by salt addition.