Real-time monitoring of cell membrane modification during supercritical CO2 pasteurization

This study addresses cell membrane permeabilization phenomena over microorganisms induced by high pressure CO2: a real-time measurement has been set-up and performed by an innovative cell fluorescent staining technique. A common yeast, S. cerevisiae was used as test-microorganism. Different sets of experiments were carried out in batch mode at 100 bar, 36 °C and different treating time (10–30 min). The change of optical signal intensity collected by an optical spectrometer indicates a progressive permeabilization of the cell envelopes during the treatment. This new analytical method provides a real-time indication of cell membrane integrity during the pasteurization process. Both the permeabilization and inactivation kinetic rates were calculated and compared; the reported data evidence a correlation between the cellular death and the CO2 permeabilization inside the cell, which, in turn, can be considered the key factor of microbial inactivation.