| Summary: | 碩士 === 東海大學 === 食品科學系 === 100 === The contamination of highly plate counts including Escherichia coli in black tea drink, one of the most popular beverages in Taiwan, has been becoming a major concern for the public health. The traditional methods for detection of E. coli include API System, Coliform Agar and Pertrifilm, etc., however, these culturing methods are excessively time-consuming and take cumbersome steps. In this study, a simple, rapid and cost-effective analytical method for the detection of E. coli and coliforms was established. Cultures of E. coli, coliforms and non-colifoms gram-negative bacteria were tested using the electrochemical method. The amperometric measurements were performed in the selective medium by the addition of black tea drink at a working potential of 0.3 V or 0.5 V and temperatures at 37 ℃. The results showed that a linear relationship exists between the logarithm of the bacterial concentration (over the range of 101 to 108 CFU/mL) and the detection time (DT). The addition of black tea drink into the selective medium caused the release of electrochemical active substances in microorganisms and produced a significant signal through the electrode reaction. The correlation coefficient (R2) was 0.9354 and 0.9144 for the detection of E. coli and coliforms, respectively. The DT obtained from the proposed method is about 10 hours, which is shorter than those by traditional culturing methods. The proposed electrochemical method could both rapidly and sensitively determine the concentration of E. coli and coliforms in black tea drink samples.
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