Different electrical conductivity systems were used in comparison to follow the electrical conductivity (EC) in reconstituted skim milk (RSM) during acidification. The effects of protein and fat concentrations on the EC, lactic acid production, and soluble Ca solubilization in dairy blends, inoculated with a thermophilic starter, were evaluated. An industrial conductivity system used in automatic temperature compensation mode at 25 °C and coupled with a non-glass probe was as appropriate as a laboratory conductivity system coupled with a glass probe to follow EC evolution during acidification of RSM. The relationships between pH and EC, pH and lactic acid, pH and different soluble minerals, and pH and viscosity were curvilinear in RSM. However, in a fermented dairy blend, relationships between pH and EC, and pH and lactic acid production could be linearized, and pH evolution could be predicted by measuring EC evolution. Among soluble minerals, the contribution of soluble Ca to EC seemed to be more important than soluble P, Mg, K and Na. In a dairy blend, protein concentrations affected the EC, the lactic acid production, and the soluble Ca, while fat concentration had no influence. The contribution of proteins could be standardized by expressing data per gram of protein.