紅茶是台灣最受歡迎的飲品之一，但常有生菌數過高、大腸桿菌群超標等問題。傳統檢測大腸桿菌及大腸桿菌群的標準方法包括：API system、Coliform agar及PetrifilmTM 等，但程序耗時且繁瑣。本研究旨在建立一套簡單快速、成本低廉的電化學檢測方法以應用於紅茶之微生物檢測；以大腸桿菌 (群) 及非大腸桿菌群之革蘭氏陰性菌 (在LST選擇性培養基/紅茶中，Lauryl Sulfate Tryptose Broth，簡稱LST) 為檢測對象，操作條件分別設定在0.3及0.5 V，維持37℃ ，菌體在代謝過程會產生具電化學活性的代謝產物，可誘發電極反應產生電流訊號。本電化學法並可藉由LST中的乳糖不同之代謝效應以分離大腸桿菌群及其他革蘭氏陰性菌，也可透過排除LST之緩衝溶液以區分大腸桿菌及大腸桿菌群。結果顯示紅茶中之所有受檢菌體濃度 (101至108 CFU/ml) 與檢測時間均呈線性關係 (R2均>0.9)，本電化學法檢測均與現行傳統方法結果相符，所需DT也可縮短約10時。整體而言，本電化學法簡單、快速具實用性，值得深入探討。

Black tea is one of the most popular beverages in Taiwan, but the presence of high bacteria counts or coliform counts exceeding the criteria in tea has become the most common food-safety issue. Conventional standard methods for detecting Escherichia coli or coliforms include API System, Coliform Agar and PertrifilmTM, etc. However, these methods are excessively time-consuming and cumbersome. The aim of this study is to establish a simple, rapid and cost-effective electroanalytical method for detecting microorganism in black tea. E. coli, coliforms and non-coliforms gram-negative bacteria (in LST (Lauryl Sulfate Tryptose Broth) selective medium/black tea) were detected using the electrochemical method. The amperometric measurements were performed at a potential of 0.3 V or 0.5 V and 37℃. Bacteria can produce electroactive metabolites through their metabolic processes, which can induce the electrode reactions and the consequent electric current is generated. Furthermore, our electrochemical approach can distinguish coliforms from non-coliforms gram-negative bacteria and distinguish E. coli from coliforms probably through differential LST-lactose metabolisms and removing the buffer system from LST medium, respectively. All the microbial concentrations (ranging from 101 to 108 CFU/mL) were linearly correlated to the detection time (DT) with correlation coefficients greater than 0.9. The results obtained by the proposed method are consistent with those obtained by conventional method. The DT required was approximately 10 hours earlier as compared to the conventional method. Our electrochemical approach has proven easy, fast and reliable in determining bacteria in black tea and is considered appropriate for further practical study.