Killing of microorganisms by pulsed electric fields

Area of Science:

• Food science and technology
• Microbiology
• Biophysics

Background:

• Pulsed electric fields (PEF) offer a potential non-thermal processing method for food preservation.
• Understanding PEF's lethal effects on microorganisms is crucial for its application in the food industry.
• Assessing PEF's impact on food quality and cellular components is necessary for practical implementation.

Purpose of the Study:

• To investigate the lethal effects of PEF on various microorganisms (bacteria, yeast, spores) in different media.
• To determine the critical parameters (electric field strength, treatment time) for effective microbial inactivation.
• To evaluate the impact of PEF on food components (proteins, enzymes, vitamins) and sensory properties.

Main Methods:

• Exposure of microbial suspensions in buffer solutions and liquid foodstuffs to PEF.
• Quantification of surviving vegetative cells and spores using viable cell counts.
• Analysis of food components and sensory evaluation of PEF-treated foodstuffs.

Main Results:

• PEF treatment reduced vegetative cell counts by over four orders of magnitude (>99.99%).
• Endospores and ascospores showed limited inactivation.
• Inactivation efficacy depended on electric field strength, treatment time, and medium properties (e.g., acidity).
• Minimal impact on whey proteins, enzymes, vitamins, and taste of foodstuffs was observed.
• Yeast cells were not disintegrated for intracellular product harvesting.

Conclusions:

• PEF is a highly effective method for inactivating vegetative microorganisms in acidic and thermosensitive liquid foods.
• PEF offers a promising non-thermal alternative for microbial decontamination in food processing.
• PEF is not suitable for complete microbial cell disintegration to release intracellular products.