Use of conductimetry to evaluate Lactobacillus delbrueckii ssp. bulgaricus subjected to freeze-drying

The survival rate of Lactobacillus delbrueckii ssp. bulgaricus and the lactic acid production in milk after freeze-drying was evaluated by viability and conductimetric assays. Most strains showed a typical conductance before freeze-drying which became flat after the process. Differences in Detection Time (DT) before and after lyophilization (expressed as Delta DT) were in the range of 0.8-19.8 according to the suspension medium and the strain under study. Both the survival rate and the acidifying capacity of the cultures were better preserved when sodium glutamate (as cryoprotector) was added to skimmed milk.