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Effect of ionic strength on the inactivation of micro-organisms by microwave irradiation

K Watanabe1, Y Kakita, N Kashige

  • 1Laboratory of Microbiology, Faculty of Pharmaceutical Sciences, Fukuoka, Japan. kwatanabe@fukuaka-u.ac.jp

Letters in Applied Microbiology
|July 8, 2000
PubMed

Insights

Microwave irradiation effectively inactivates microbial cells like Escherichia coli and Staphylococcus aureus. Microbial inactivation rates correlate with temperature increases and are influenced by salt concentrations, not sugars.

Area of Science:

  • Microbiology
  • Food Science
  • Biophysics

Background:

  • Microbial contamination poses significant risks in various settings.
  • Effective sterilization methods are crucial for public health and safety.
  • Microwave irradiation is a potential non-thermal or thermal inactivation technology.

Purpose of the Study:

  • To investigate the efficacy of microwave irradiation in inactivating microbial cells.
  • To determine the influence of salt and sugar on microwave-induced inactivation.
  • To explore the relationship between microwave heating, ionic solutions, and cell inactivation.

Main Methods:

  • Suspension of microbial cells (Escherichia coli, Staphylococcus aureus, Candida albicans) in phosphate buffer.
  • Application of microwave irradiation at 2450 MHz.
  • Varying concentrations of NaCl, KCl, and sucrose.
  • Monitoring cell inactivation rates and temperature changes.
  • Measurement of electroconductivity and dielectric loss.

Main Results:

  • Microwave irradiation at 2450 MHz inactivated Escherichia coli, Staphylococcus aureus, and Candida albicans.
  • Cell inactivation rate was directly proportional to the temperature increase during irradiation.
  • NaCl and KCl enhanced inactivation rates, with optimal effects at 0.5-1.0 mol l-1.
  • Sucrose did not affect the inactivation rates.
  • Highest end-point temperatures were observed at optimal salt concentrations.

Conclusions:

  • Microwave irradiation is an effective method for microbial inactivation.
  • Ionic strength significantly modulates microwave-induced cell inactivation.
  • Temperature and solution properties (electroconductivity, dielectric loss) are key factors in microwave heating and inactivation efficacy.

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