How does the application of pulsed electric fields (PEF) impact cellular structures to achieve microbial inactivation?

Pulsed electric fields (PEF) technology inactivates microorganisms by applying short bursts of high-voltage electricity to food products. This process primarily disrupts the cell membrane of microorganisms, leading to their inactivation without significant heating. The electric field creates an electrical potential difference across the cell membrane, exceeding its dielectric strength. Dielectric strength is the maximum electric field that a material can withstand before it breaks down and becomes conductive. This causes electroporation, the formation of pores or channels in the cell membrane. These pores compromise the membrane's integrity, leading to leakage of intracellular contents and ultimately cell death. The effectiveness of PEF depends on factors such as the electric field strength, pulse duration, pulse frequency, and the electrical conductivity of the food product. For example, PEF can be used to pasteurize fruit juices by inactivating spoilage bacteria and yeasts without causing significant changes in flavor or nutritional content. Gram-positive bacteria are typically more resistant to PEF than Gram-negative bacteria due to differences in their cell wall structure. Spores are generally more resistant to PEF than vegetative cells. PEF is often used in combination with other preservation methods, such as mild heat or antimicrobial agents, to enhance its effectiveness and achieve complete microbial inactivation.