Inactivation of Escherichia coli, Saccharomyces cerevisiae, and Lactobacillus brevis in Low-fat Milk by Pulsed Electric Field Treatment: A Pilot-scale Study.

Abstract

We investigated the effects of a pulsed electric field (PEF) treatment on microbial inactivation and the physical properties of low-fat milk. Milk inoculated with Escherichia coli, Saccharomyces cerevisiae, or Lactobacillus brevis was supplied to a pilot-scale PEF treatment system at a flow rate of 30 L/h. Pulses with an electric field strength of 10 kV/cm and a pulse width of 30 μs were applied to the milk with total pulse energies of 50-250 kJ/L achieved by varying the pulse frequency. The inactivation curves of the test microorganisms were biphasic with an initial lag phase (or shoulder) followed by a phase of rapid inactivation. PEF treatments with a total pulse energy of 200 kJ/L resulted in a 4.5-log reduction in E. coli, a 4.4-log reduction in L. brevis, and a 6.0-log reduction in S. cerevisiae. Total pulse energies of 200 and 250 kJ/L resulted in greater than 5-log reductions in microbial counts in stored PEF-treated milk, and the growth of surviving microorganisms was slow during storage for 15 d at 4℃. PEF treatment did not change milk physical properties such as pH, color, or particle-size distribution (p<0.05). These results indicate that a relatively low electric-field strength of 10 kV/cm can be used to pasteurize low-fat milk.

AI evidence extraction

Main findings

Low-fat milk inoculated with E. coli, S. cerevisiae, or L. brevis was treated with PEF at 10 kV/cm (30 μs pulses) with total pulse energies 50–250 kJ/L. At 200 kJ/L, reductions were 4.5-log (E. coli), 4.4-log (L. brevis), and 6.0-log (S. cerevisiae); 200–250 kJ/L produced >5-log reductions in stored treated milk and surviving microorganisms grew slowly over 15 days at 4℃. The authors report no change in milk pH, color, or particle-size distribution (p<0.05).

Outcomes measured

• Microbial inactivation (log reductions) of Escherichia coli
• Microbial inactivation (log reductions) of Saccharomyces cerevisiae
• Microbial inactivation (log reductions) of Lactobacillus brevis
• Milk physical properties (pH, color, particle-size distribution)
• Microbial growth during storage (15 d at 4℃)

Limitations

• Pilot-scale study
• No sample size reported in abstract
• Exposure parameters reported as electric field strength and pulse energy; no EMF frequency information provided
• Statement about physical properties includes 'did not change' alongside 'p<0.05' as written in abstract, which is internally unclear

Suggested hubs

• engineering (0.78)
  Pilot-scale pulsed electric field processing parameters and performance.
• food-processing (0.72)
  Application of PEF for milk pasteurization and quality outcomes.

{
    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "pulsed electric field (PEF) food processing system",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "pulse width 30 μs; storage 15 d at 4℃ (post-treatment observation)"
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "Microbial inactivation (log reductions) of Escherichia coli",
        "Microbial inactivation (log reductions) of Saccharomyces cerevisiae",
        "Microbial inactivation (log reductions) of Lactobacillus brevis",
        "Milk physical properties (pH, color, particle-size distribution)",
        "Microbial growth during storage (15 d at 4℃)"
    ],
    "main_findings": "Low-fat milk inoculated with E. coli, S. cerevisiae, or L. brevis was treated with PEF at 10 kV/cm (30 μs pulses) with total pulse energies 50–250 kJ/L. At 200 kJ/L, reductions were 4.5-log (E. coli), 4.4-log (L. brevis), and 6.0-log (S. cerevisiae); 200–250 kJ/L produced >5-log reductions in stored treated milk and surviving microorganisms grew slowly over 15 days at 4℃. The authors report no change in milk pH, color, or particle-size distribution (p<0.05).",
    "effect_direction": "benefit",
    "limitations": [
        "Pilot-scale study",
        "No sample size reported in abstract",
        "Exposure parameters reported as electric field strength and pulse energy; no EMF frequency information provided",
        "Statement about physical properties includes 'did not change' alongside 'p<0.05' as written in abstract, which is internally unclear"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "pulsed electric field",
        "PEF",
        "low-fat milk",
        "pasteurization",
        "microbial inactivation",
        "Escherichia coli",
        "Saccharomyces cerevisiae",
        "Lactobacillus brevis",
        "pilot-scale"
    ],
    "suggested_hubs": [
        {
            "slug": "engineering",
            "weight": 0.7800000000000000266453525910037569701671600341796875,
            "reason": "Pilot-scale pulsed electric field processing parameters and performance."
        },
        {
            "slug": "food-processing",
            "weight": 0.7199999999999999733546474089962430298328399658203125,
            "reason": "Application of PEF for milk pasteurization and quality outcomes."
        }
    ]
}

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