Impedance sensor for rapid enumeration of E. coli in milk samples

Jen Tsai Liu, Kalpana Settu, Jang Zern Tsai, Ching Jung Chen

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Detection of pathogenic bacteria in dairy farms and processing plants is important for milk quality control. In this study, a simple in situ method for determining the bacterial concentration in milk was developed with an interdigitated microelectrode sensor. This method was based on a punctual measurement of the electrode-milk interface impedance change due to bacterial metabolism in the milk. The interface impedance varied predominately at low frequencies, attributed to the change on the double-layer capacitance. The detection time TD, defined as the time required to attain a -10% impedance change at 10 Hz, became a practicable means for the estimation of initial E. coli concentration in milk samples. Regression analysis resulted in a third-order polynomial relationship between the detection time and the logarithm of the initial E. coli concentration (N0, cells/ml) in a milk sample, i.e., log N0 = 11.48 - 2.33 TD + 0.288(TD)2 - 0.0154(TD)3 with R2 = 0.9988. The sensor was able to detect E. coli in milk of initial concentrations as low as 7 cells/ml. The proposed impedance sensor is suitable for determining bacterial contamination at dairy farms and processing plants.

Original languageEnglish
Pages (from-to)89-95
Number of pages7
JournalElectrochimica Acta
StatePublished - 10 Nov 2015


  • Electrochemical impedance spectroscopy
  • Escherichia coli
  • Interdigitated microelectrode
  • Milk


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