Moderate intensity Pulsed Electric Fields (PEF) as alternative mild preservation technology for fruit juice

Area of Science:

• Food Science and Technology
• Microbiology
• Biophysics

Background:

• Pulsed Electric Fields (PEF) are explored as an alternative to thermal pasteurization and high-intensity PEF for microbial inactivation.
• PEF processing involves applying electric pulses, leading to ohmic heating and potential microbial cell membrane permeabilization (electroporation).

Purpose of the Study:

• To systematically evaluate the effect of moderate intensity PEF parameters (electric field strength and pulse width) on microbial inactivation in orange juice.
• To compare the inactivation kinetics of PEF with thermal processes to differentiate between non-thermal (electroporation) and thermal effects.
• To investigate the influence of pH and medium conductivity on microbial inactivation under moderate intensity PEF conditions.

Main Methods:

• A continuous flow system was used to apply moderate intensity PEF to orange juice inoculated with various microorganisms (E. coli, L. monocytogenes, L. plantarum, S. Senftenberg, S. cerevisiae).
• Parameters varied included electric field strength (E) and pulse width (τ).
• Inactivation kinetics were compared to equivalent thermal treatments. Further studies on E. coli and L. monocytogenes in watermelon juice and coconut water examined pH and conductivity effects.

Main Results:

• Moderate intensity PEF (2.7 kV/cm, 15-1000 μs) proved more effective for microbial inactivation than high intensity PEF (10 kV/cm, 2 μs).
• Non-thermal inactivation effects attributed to electroporation were observed at both high (20 kV/cm, 2 μs) and moderate (2.7 kV/cm, 15-1000 μs) intensity PEF.
• Under moderate intensity PEF, microbial inactivation was independent of pH (3.8-6.0) in various matrices, unlike high intensity PEF where pH is critical.

Conclusions:

• Moderate intensity PEF (2.7 kV/cm, 15-1000 μs) demonstrates significant potential for industrial application in preserving fruit juices and pH-neutral liquid foods.
• The pH independence suggests a distinct inactivation mechanism for moderate intensity PEF compared to high intensity PEF.
• Further research into the specific mechanisms of moderate intensity PEF inactivation is warranted.