Effect of microwave radiation on inactivation of Clostridium sporogenes (PA 3679) spores.

Abstract

Three techniques for studying effects of microwave radiation on microorganisms were introduced. Spores of Clostridium sporogenes (PA 3679) were chosen as a test organism because the kinetic parameters for thermal inactivation are well known and because of the importance of the genus Clostridium to the food industry. For the first technique, a specially designed kinetics vessel was used to compare inactivation rates of microwave-heated and conventionally heated spores at steady-state temperatures of 90, 100, and 110 degrees C. Rates were found to be similar at the 95% confidence level. The second and third techniques were designed to study the effect of relatively high power microwave exposure at sublethal temperatures. In the second approach, the suspension was continuously cooled via direct contact with a copper cooling coil in a well-mixed vessel, outside the microwave oven. The suspension was pumped through a Teflon loop in the oven, where it continuously absorbed approximately 400 W of microwave power. Inactivation occurred in both irradiated and unirradiated samples. It was suspected that copper ions entered the suspension from the copper coil and were toxic to the spores. The fact that the results were similar, however, implied the absence of nonthermal microwave effects. In the third approach, the copper coil was replaced with a silicone tubing loop in a microwave transparent vessel. The suspension was continuously irradiated at 150 W of microwave power. No detectable inactivation occurred. Results indicated that the effect of microwave energy on viability of spores was indistinguishable from the effect of conventional heating.

AI evidence extraction

Main findings

Using a kinetics vessel at steady-state temperatures of 90, 100, and 110°C, inactivation rates for microwave-heated and conventionally heated spores were similar at the 95% confidence level. In a cooled-loop setup absorbing ~400 W microwave power, inactivation occurred in both irradiated and unirradiated samples and was suspected to be due to copper ion toxicity; similar results were interpreted as implying absence of nonthermal microwave effects. With a silicone tubing loop and continuous irradiation at 150 W, no detectable inactivation occurred; overall, microwave effects on spore viability were indistinguishable from conventional heating.

Outcomes measured

• Spore inactivation rate/viability under microwave heating vs conventional heating
• Inactivation under high-power microwave exposure at sublethal temperatures

Limitations

• Microwave frequency not reported in abstract
• Potential confounding from copper ion contamination in the second technique
• Sample size and exposure duration not reported in abstract

{
    "study_type": "other",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Clostridium sporogenes (PA 3679) spores",
    "sample_size": null,
    "outcomes": [
        "Spore inactivation rate/viability under microwave heating vs conventional heating",
        "Inactivation under high-power microwave exposure at sublethal temperatures"
    ],
    "main_findings": "Using a kinetics vessel at steady-state temperatures of 90, 100, and 110°C, inactivation rates for microwave-heated and conventionally heated spores were similar at the 95% confidence level. In a cooled-loop setup absorbing ~400 W microwave power, inactivation occurred in both irradiated and unirradiated samples and was suspected to be due to copper ion toxicity; similar results were interpreted as implying absence of nonthermal microwave effects. With a silicone tubing loop and continuous irradiation at 150 W, no detectable inactivation occurred; overall, microwave effects on spore viability were indistinguishable from conventional heating.",
    "effect_direction": "no_effect",
    "limitations": [
        "Microwave frequency not reported in abstract",
        "Potential confounding from copper ion contamination in the second technique",
        "Sample size and exposure duration not reported in abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "nonthermal effects",
        "thermal inactivation",
        "Clostridium sporogenes",
        "spores",
        "food microbiology",
        "conventional heating"
    ],
    "suggested_hubs": []
}

Comments

Log in to comment.

No comments yet.