Critical electric field strengths of onion tissues treated by pulsed electric fields.

Abstract

The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (E(c)) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-μs pulses indicate that breakdown of the plasma membrane occurs above E(c)= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either E(c)= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n≥10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses.

AI evidence extraction

Main findings

For 100-μs pulses, plasma membrane breakdown was detected above a critical field strength of 67 V/cm for 10 pulses, while tonoplast membrane breakdown was detected above 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. A single pulse up to 333 V/cm produced no observable effect on measured properties, whereas significant differences were observed for n≥10; the minimum field strength needed to cause measurable change decreased as the number of pulses increased.

Outcomes measured

• cellular integrity (membrane rupture/breakdown thresholds)
• texture
• electrical properties/characteristics
• ion leakage rate
• enzymatically formed pyruvate (alliinase activity; indicator of tonoplast breakdown)

Limitations

• Sample size not reported in the abstract.
• Study is on plant tissue (onions), limiting direct relevance to human health outcomes.
• Exposure parameters beyond pulse width and field strength (e.g., waveform details) are not provided in the abstract.

{
    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "pulsed electric fields (PEF) treatment",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "100-μs pulses; varying number of pulses (single pulse, 10 pulses, 100 pulses)"
    },
    "population": "Onion tissues (Ranchero and Sabroso onions; Allium cepa L.)",
    "sample_size": null,
    "outcomes": [
        "cellular integrity (membrane rupture/breakdown thresholds)",
        "texture",
        "electrical properties/characteristics",
        "ion leakage rate",
        "enzymatically formed pyruvate (alliinase activity; indicator of tonoplast breakdown)"
    ],
    "main_findings": "For 100-μs pulses, plasma membrane breakdown was detected above a critical field strength of 67 V/cm for 10 pulses, while tonoplast membrane breakdown was detected above 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. A single pulse up to 333 V/cm produced no observable effect on measured properties, whereas significant differences were observed for n≥10; the minimum field strength needed to cause measurable change decreased as the number of pulses increased.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in the abstract.",
        "Study is on plant tissue (onions), limiting direct relevance to human health outcomes.",
        "Exposure parameters beyond pulse width and field strength (e.g., waveform details) are not provided in the abstract."
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "pulsed electric fields",
        "PEF",
        "onion",
        "Allium cepa",
        "membrane breakdown",
        "plasma membrane",
        "tonoplast",
        "critical electric field strength",
        "ion leakage",
        "texture",
        "pyruvate",
        "alliinase"
    ],
    "suggested_hubs": []
}

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