THE USE OF ELECTRICAL-CONDUCTIVITY TO FOLLOW ACIDIFICATION OF DAIRY BLENDS

Different electrical conductivity systems, used in comparison to follo w the electrical conductivity (EC) in reconstituted skim milk (RSM) du ring acidification. The effects of protein and fat concentrations on t he EC, lactic acid production, and soluble Ca solubilization in dairy blends, inoculated with a thermophilic starter, were evaluated An indu strial conductivity system used in automatic temperature compensation mode at 25 degrees C and coupled, a non-glass probe was as appropriate as a laboratory conductivity system coupled with a glass probe to fol low EC evolution during acidification of RSM. The relationships betwee n pH and EC, pH and lactic acid, pH and different soluble minerals, an d pH and viscosity were curvilinear in RSM. However, in a fermented da iry blend, relationships between pH and EC, and pH and lactic acid pro duction could be linearized, and pH evolution could be predicted bq, m easuring EC evolution. Among soluble minerals, the contribution of sol uble 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 hall no influence. The contribution of proteins could be standardized by expr essing data per gram of protein.