Pulsed light inactivation of Bacillus subtilis vegetative cells in suspensions and spices

The aim of our study was to assess the impact of a pulsed light (PL) technology on Bacillus subtilis grown on two model matrixes, through bacterial inactivation and cell integrity. First, the effect of PL treatment on B. subtilis vegetative cells in liquid state was evaluated. We found that PL treatment leads to 8 log reduction of B. subtilis vegetative cells while bacterial morphology was not affected. Second, spices, among which ground caraway, ground red pepper and ground black pepper were artificially inoculated with a known concentration of B. subtilis in vegetative state and then exposed to PL. In this case, PL treatment leads to a bacterial reduction of about 1 log and serious damage of the microorganisms parietal structure occurred. To conclude, this work highlights that pulsed light has a potential for inactivation of B. subtilis in both, liquid and dry state but through different mechanisms.