Inactivation of L. plantarum in a PEF microreactor: The effect of pulse width and temperature on the inactivation

This article describes the inactivation of Lactobacillus plantarum by pulsed electric fields (PEF) in a microfluidic reactor. The microreactor has the specific advantage that the field intensity can be extremely high with accurate control and measurement of the pulse shape, combined with good temperature controllability. It is demonstrated that the temperature increase due to the ohmic heating of the fluid during treatment is marginal, thereby making this an excellent device for decoupling the temperature and electric field effects of PEF. Flow cytometry measurements showed that the electroporation of cells by PEF is a gradual effect. Reducing the pulsewidth at equal energy inputs did not show a change in inactivation. Higher temperatures showed higher inactivation rates. The effect of the temperature and the electric field strength could be described by a model that combines an Arrhenius equation for temperature dependency with either a Huelsheger or an activation energy based model for electric field dependency.Industrial relevanceThe product temperature is increasing during pulsed electric field treatment due to ohmic heating. Up to now, it was not possible to distinguish between the electric and heat effects that take place in the reactor. With the presented PEF microreactor, it was possible to make this distinction, which can help in the development of new, optimized PEF reactors.