Effect of Growth Stage and Processing Temperature on the Inactivation of E. coli by Pulsed Electric Fields.

Abstract

The effect of growth stage and processing temperature on the inactivation of Escherichia coli subjected to pulsed electric fields was studied. Simulated milk ultrafiltrate (SMUF) inoculated with E. coli was subjected to high-intensity exponentially decaying or square-wave pulses with a field strength of 36 kV/cm and pulse duration of 2 μs at selected temperatures ranging between 3 and 40°C. The rate of inactivation increased with an increase in the processing temperature. Furthermore, square-wave pulses were more lethal than exponentially decaying pulses. At 7°C after 100 μs, square-wave pulses produced a 99% decrease while exponential decaying pulses produced a 93% decrease in bacterial cell population. Cells harvested at lag, log, and stationary phases were subjected to 2 and 4 pulses with an electric field intensity of 36 kV/cm at 7°C. Logarithmic-phase cells were more sensitive than stationary- and lag-phase cells to the pulsed electric field treatment.

AI evidence extraction

Main findings

E. coli in simulated milk ultrafiltrate exposed to pulsed electric fields (36 kV/cm, 2 μs pulses) showed increased inactivation rates at higher processing temperatures (3–40°C). Square-wave pulses were more lethal than exponentially decaying pulses (at 7°C after 100 μs: 99% vs 93% decrease). Log-phase cells were more sensitive than stationary- and lag-phase cells under the tested conditions (2 and 4 pulses at 7°C).

Outcomes measured

• E. coli inactivation (reduction in bacterial cell population)
• Effect modification by processing temperature
• Effect modification by growth stage (lag/log/stationary)
• Comparison of pulse waveform lethality (square-wave vs exponentially decaying)

Limitations

• No sample size reported in abstract
• Study conducted in simulated milk ultrafiltrate rather than in vivo/clinical setting
• Only one field strength (36 kV/cm) and limited pulse conditions described in abstract
• Outcomes limited to bacterial inactivation; no human health outcomes

{
    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "pulsed electric fields (food processing)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "pulse duration 2 μs; total treatment time example: 100 μs; 2 and 4 pulses"
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "E. coli inactivation (reduction in bacterial cell population)",
        "Effect modification by processing temperature",
        "Effect modification by growth stage (lag/log/stationary)",
        "Comparison of pulse waveform lethality (square-wave vs exponentially decaying)"
    ],
    "main_findings": "E. coli in simulated milk ultrafiltrate exposed to pulsed electric fields (36 kV/cm, 2 μs pulses) showed increased inactivation rates at higher processing temperatures (3–40°C). Square-wave pulses were more lethal than exponentially decaying pulses (at 7°C after 100 μs: 99% vs 93% decrease). Log-phase cells were more sensitive than stationary- and lag-phase cells under the tested conditions (2 and 4 pulses at 7°C).",
    "effect_direction": "harm",
    "limitations": [
        "No sample size reported in abstract",
        "Study conducted in simulated milk ultrafiltrate rather than in vivo/clinical setting",
        "Only one field strength (36 kV/cm) and limited pulse conditions described in abstract",
        "Outcomes limited to bacterial inactivation; no human health outcomes"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "pulsed electric fields",
        "E. coli",
        "inactivation",
        "processing temperature",
        "growth stage",
        "square-wave pulses",
        "exponentially decaying pulses",
        "food processing"
    ],
    "suggested_hubs": []
}

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