Abstract
Pulsed magnetic field (PMF) has been proposed as a non-thermal technology for inactivation of microorganisms in food. The changes in intracellular Ca2+ concentration in microorganisms may contribute to explain the inactivation mechanism by PMF. A fluorescence method for evaluating the intracellular Ca2+ concentration in Listeria monocytogenes was established to reveal the effect of PMF on the intracellular Ca2+ level in cell. Fluo-4 AM, a fluorescent calcium assay reagent, was used to determine the intracellular Ca2+ concentration in L. monocytogenes. The results showed that Fluo-4 AM was successfully loaded into L. monocytogenes and could be used to determine the concentration of intracellular free Ca2+ level. The optimal loading temperature and time were 37 °C and 120 min, respectively. After exposure to PMF, intracellular Ca2+ concentration in L. monocytogenes increased by amounts varying between 27.5 and 45.2%. In addition, laser confocal scanning microscope (LCSM) analysis conformed that the Ca2+ fluorescence intensity in L. monocytogenes increased after PMF treatment, indicating that large amounts of exocellular Ca2+ permeated into the cells. Therefore, it can be inferred that PMF may increase the permeability of the cell membrane and promote Ca2+ transmembrane behavior. These results help to explore the inactivation mechanism of microorganism treated by PMF from the angle of the intracellular Ca2+ concentration.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
