Cold-set gels of whey protein isolate (WPI) were produced. The cold gelation was induced through the addition of magnesium chloride whose cation is an alternative to the most common cations used in this kind of gelation. A phase diagram for denatured WPI in magnesium was determined by varying protein and salt concentrations. In this diagram the protein and cation concentrations varied from 0.3 to 8.0 wt % and 1 to 75 mM, respectively. The viscoelastic behaviour of the WPI was analysed, whereas gels elastic properties were measured by means of texture tests. Mathematical manipulation of the experimental data relative to the puncture tests was made in order to obtain the Young’s modulus for each cold-set gel.